U.S. patent application number 16/703081 was filed with the patent office on 2020-04-02 for particles containing an opioid receptor antagonist and methods of use.
The applicant listed for this patent is The University of Chicago. Invention is credited to Chun-Su YUAN.
Application Number | 20200101026 16/703081 |
Document ID | / |
Family ID | 1000004509806 |
Filed Date | 2020-04-02 |
United States Patent
Application |
20200101026 |
Kind Code |
A1 |
YUAN; Chun-Su |
April 2, 2020 |
PARTICLES CONTAINING AN OPIOID RECEPTOR ANTAGONIST AND METHODS OF
USE
Abstract
Particles comprising an opioid receptor antagonist as well as
methods of their use and methods of their preparation are provided
herein. Such particles may be used for treating and preventing
opioid-induced side effects in patients, and may be provided to
chronic opioid users as well.
Inventors: |
YUAN; Chun-Su; (Chicago,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The University of Chicago |
Chicago |
IL |
US |
|
|
Family ID: |
1000004509806 |
Appl. No.: |
16/703081 |
Filed: |
December 4, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15835181 |
Dec 7, 2017 |
10507188 |
|
|
16703081 |
|
|
|
|
13001146 |
May 18, 2011 |
|
|
|
PCT/US09/47372 |
Jun 15, 2009 |
|
|
|
15835181 |
|
|
|
|
61077242 |
Jul 1, 2008 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61K 9/5161 20130101;
A61K 31/485 20130101; A61K 31/00 20130101; A61K 9/5138
20130101 |
International
Class: |
A61K 31/00 20060101
A61K031/00; A61K 9/51 20060101 A61K009/51; A61K 31/485 20060101
A61K031/485 |
Claims
1. An enterically-coated particle comprising at least one opioid
receptor antagonist, at least one hydrophilic additive that is
negatively charged at acidic and neutral pH, and at least one
hydrophilic additive is positively charged at acidic and neutral
pH.
2. The enterically-coated particle of claim 1, wherein the
positively-charged opioid receptor antagonist is a peripheral
opioid antagonist.
3. The enterically-coated particle of claim 2, wherein the
peripheral opioid receptor antagonist is a quaternary morphinan
derivative, a carboxy-normorphinan derivative, or a quaternary
benzomorphan derivative.
4. The enterically-coated particle of claim 3, wherein the
quaternary morphinan is a quaternary salt of N-methylnaltrexone,
N-methylnaloxone, N-methylnalorphine, N-diallylnormorphine,
N-allyllevellorphan, or N-methylnalmefene.
5. The enterically-coated particle of claim 3, wherein the
quaternary benzomorphan derivative is selected from the group
consisting of
2'-hydroxy-5,9-dimethyl-2,2-diallyl-6,7-benzomorphanium bromide;
2'-hydroxy-5,9-dimethyl-2-n-propyl-2-allyl-6,7-benzomorphanium
bromide;
2'-hydroxy-5,9-dimethyl-2-n-propyl-2-propargyl-6,7-benzomorphanium
bromide; and
2'-acetoxy-5,9-dimethyl-2-n-propyl-2-allyl-6,7-benzomorphanium
bromide.
6. The enterically-coated particle of claim 1, wherein the particle
comprises two or more opioid receptor antagonists.
7. The enterically-coated particle of claim 1, wherein the
hydrophilic additive that is negatively charged at acidic and
neutral pH is pentasodium tripolyphosphate (TPP).
8. The enterically-coated particle of claim 1, wherein the at least
one hydrophilic additive is positively charged at acidic and
neutral pH is a polymer.
9. The enterically-coated particle of claim 1, wherein the at least
one hydrophilic additive is positively charged at acidic and
neutral pH is chitosan.
10. The enterically-coated particle of claim 1, wherein a diameter
of the enterically-coated particle is between about 30-1000 nm.
11. The enterically-coated particle of claim 1, wherein a weight
percentage of total opioid receptor antagonist in the
enterically-coated particle ranges from about 8-35.
12. The enterically-coated particle of claim 1, wherein the enteric
coating comprises both a polymethacrylate and a distilled
acetylated monoglyceride.
13. The enterically-coated particle of claim 1, further defined as
a time release composition, wherein the time release composition is
formulated to release the opioid receptor antagonist over time.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S.
application Ser. No. 15/835,181 filed Dec. 7, 2017, which is a
continuation from U.S. application Ser. No. 13/001,146 filed May
18, 2011, which is a 371 national stage entry of PCT/US09/47372
filed Jun. 15, 2009, which claims the benefit of priority to U.S.
Application No. 61/077,242, filed Jul. 1, 2008; the entire contents
of each application being incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to the fields of opioid
receptor antagonists and drug delivery. In general, particles
comprising an opioid receptor antagonist are described along with
methods of their use.
2. Description of Related Art
[0003] Opioids are effective analgesics. However, their use is
associated with a number of undesirable side effects. One such
effect is constipation. Opioid-induced changes in gastrointestinal
motility are almost universal when these drugs are used to treat
pain, and at times may limit their use, leaving the patient in
pain. Common treatments of bulking agents and laxatives have
limited efficacy and may be associated with side effects such as
electrolyte imbalances.
[0004] One treatment for opioid side effects is the use of opioid
receptor antagonists which cross the blood-brain-barrier, or which
are administered directly into the central nervous system. Opioid
receptor antagonists such as naltrexone and naloxone have been
administered intramuscularly or orally to treat opioid induced side
effects. Naltrexone and naloxone are highly lipid soluble and
rapidly diffuse across biological membranes, including the
blood-brain barrier. However, naltrexone, naloxone, nalmefene, and
other opioid receptor antagonists which may reverse many opioid
side effects have a narrow therapeutic window before they are
observed to reverse the desired analgesic effect of the opioid
being used.
[0005] Many quaternary amine opioid receptor antagonist
derivatives, such as methylnaltrexone (MNTX), do not reduce the
analgesic effect of opioids when administered peripheral to the
central nervous system. These quaternary amine opioid receptor
antagonist derivatives, which have a relatively higher polarity and
reduced lipid solubility when compared to the tertiary forms of the
drugs, were specifically developed to not traverse the blood-brain
barrier or to traverse it at a greatly reduced rate. However, high
levels of MNTX in the plasma can lead to undesirable side effects
such as orthostatic hypotension.
[0006] In April 2008, the United States FDA approved the use of
methylnaltrexone bromide (Relistor.TM.) as a subcutaneous injection
to help restore bowel function in patients with late-stage,
advanced illness who are receiving opioids on a continuous basis to
help alleviate their pain. In particular, the drug is designed to
alleviate constipation in patients who have not successfully
responded to laxative therapy.
[0007] Alternative methods of providing methylnaltrexone and other
opioid receptor antagonists to patients are desirable, such as
methods that allow lower doses of the antagonist to be delivered
but with comparable efficacy, and methods less intrusive than
subcutaneous injection.
SUMMARY OF THE INVENTION
[0008] The present invention provides methods and compositions
involving particles comprising an opioid receptor antagonist. In
some embodiments, these particles allow for enhanced effects on
opioid-induced bowel dysfunction and other indications. For
example, particles of the present invention may result in improved
absorption of the opioid receptor antagonist into the circulatory
system compared to traditional formulations, thus resulting in a
decrease in the dose required to reach therapeutic plasma levels.
The particles may also be employed in preventative methods as well,
such as to prevent opioid-induced side effects. Moreover, the
opioid responsible for the opioid-induced effects may be an
exogenously administered opioid, or an endogenous opioid that is
produced by a patient in response to, for example, abdominal
surgery. Chronic opioid users may also benefit from receiving
particles of the present invention. Particles may comprise enteric
coatings and/or time-release agents to assist in targeted or
controlled absorption of the opioid receptor antagonist.
[0009] As explained in further detail below, a particle may
comprise only one type of particle ("homoparticulate"), or a
particle may comprise two or more types of particles
("heteroparticulate"). Accordingly, the term "particle" encompasses
both homo- and heteroparticulate particles. A "type" of particle
refers to a particle comprising a particular set of ingredients.
Thus, two different types of particles will have two different sets
of ingredients (e.g., one particle comprises an opioid receptor
antagonist and one particle does not). If two particles contain the
same ingredients but the ratio of ingredients differs, the two
particles are still considered to be of the same "type."
[0010] As will be explained, it is to be understood that a particle
of the present invention comprising an opioid receptor antagonist
may include, but is not limited to, a homoparticulate particle, a
heteroparticulate particle, a particle that comprises a single
particle, a particle that comprises two or more particles, an
enterically coated particle, a particle comprising a time-release
agent, or a particle comprising any other property or ingredient
described herein or any combination of these properties or
ingredients, except for combinations of particles whose definitions
(provided below) are mutually exclusive (e.g., a particle cannot
simultaneously be a homoparticulate particle and a
heteroparticulate particle). Any of these particles may be
comprised in a pharmaceutical composition, as described herein,
and/or may be employed in any methods of making, administration,
and/or use as described herein.
[0011] Accordingly, one general aspect of the present invention
contemplates a particle comprising an opioid receptor antagonist.
Opioid receptor antagonists are described herein. Another general
aspect of the present invention contemplates a particle comprising
an opioid receptor antagonist and chitosan. Yet another general
aspect of the present invention contemplates an enterically coated
particle that comprises at least one opioid receptor antagonist.
Any particle discussed herein may further comprise at least one
additive. Such additives are described herein. The diameter of any
particle described herein may be between about 30-1000 nm or
higher, as that range is described herein. In certain embodiments,
a homoparticulate particle is contemplated. In certain embodiments,
a heteroparticulate particle is contemplated.
[0012] An opioid receptor antagonist that is comprised in any
particle of the present invention may be, for example, a peripheral
opioid antagonist. In certain embodiments, the opioid receptor
antagonist may be a quaternary or tertiary morphinan derivative, a
piperidine-N-alkylcarboxylate, a carboxy-normorphinan derivative,
or a quaternary benzomorphan. The quaternary morphinan may be, for
example, a quaternary salt of N-methylnaltrexone, N-methylnaloxone,
N-methylnalorphine, N-diallylnormorphine, N-allyllevellorphan, or
N-methylnalmefene. In particular embodiments, the peripheral opioid
receptor antagonist is methylnaltrexone. In certain embodiments, a
particle comprises two or more opioid receptor antagonists. In
certain embodiments, the weight percentage of total opioid receptor
antagonist in the particle ranges from about, at most about, or at
least about 0.1-30%. In certain embodiments, the weight percentage
of total opioid receptor antagonist is about 0.1%, 0.25%, 0.5%,
0.75%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%,
15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%,
28%, 29%, or 30%, or any range derivable therein. The weight
percentage of total opioid receptor antagonist in the particle may
range higher than 30%, in certain embodiments. In certain
embodiments, the weight percentage may be about, at least about, or
at most about 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%,
85%, 90%, 95%, or 99%, or any range derivable therein.
[0013] As noted above, a particle of the present invention may
comprise an additive. Additives that may be employed are described
herein. An additive may comprise a polymer. An additive may
comprise, for example, a polysaccharide. An additive may comprise,
for example, a polyphosphate. In certain embodiments, at least one
additive is a hydrophobic additive. Hydrophobic additives are
defined herein. In certain embodiments, at least one additive is a
hydrophilic additive. Hydrophilic additives are defined herein.
More than one additive may be employed, as described herein. For
example, a particle may comprise at least two hydrophilic
additives. A hydrophilic additive may, for example, be positively
charged at acidic and neutral pH. Acidic pH refers to a pH of less
than 7.0. In certain embodiments, "acidic pH" refers to about or at
most about 6.5, 6.0, 5.5, 5.0, 4.5, 4.0, 3.5, 3.0, 2.5, 2.0, 1.5,
1.0, 0.5 or lower, or any range derivable therein. A hydrophilic
additive that is positively charged at acidic and neutral pH may
be, for example, chitosan. Neutral pH refers to a pH of about 7.0.
In certain embodiments, a hydrophilic additive may be negatively
charged at basic and neutral pH. As used herein, a basic pH refers
to a pH of greater than 7.0. In certain embodiments, "basic pH"
refers to about or at least about 7.5, 8, 8.5, 9, 9.5, 10, 10.5,
11, 11.5, 12, 12.5, 13, 13.5, 14, or higher, or any range derivable
therein. A hydrophilic additive may be negatively charged at acidic
and neutral pH, in certain embodiments. Such an additive may be,
for example, a polyphosphate, such as pentasodium tripolyphosphate
(TPP). In certain embodiments, at least one hydrophilic additive is
a hydrophilic additive that is positively charged at acidic and
neutral pH, and at least one second hydrophilic additive is further
defined as a hydrophilic additive that is negatively charged at
acidic and neutral pH. In certain embodiments, two hydrophilic
additives employed in a particle of the present invention are
chitosan and TPP.
[0014] Ratios of additives that may be used in particles of the
present invention are described herein. For example, the ratio of
chitosan:TPP may range between about 5:9 to about 50:9 (w/w). In
certain embodiments, the ratio of chitosan:TPP:opioid receptor
antagonist is between about 5:9:4 to 50:9:32 (w/w/w). In certain
embodiments, the ratio of chitosan:TPP:opioid receptor antagonist
is between about 5:9:4 to 50:9:32 (w/w/w). In certain embodiments,
the ratio of chitosan:TPP:opioid receptor antagonist is between
about 25:9:4 and 25:9:32 (w/w/w). In certain embodiments, the ratio
of chitosan:TPP:opioid receptor antagonist is about 5:1.8:3.2
(w/w/w).
[0015] Any particle of the present invention may comprise an
enteric agent, as described herein. Accordingly, any particle of
the present invention may be comprised in an enteric coating to
form an enterically coated particle. As noted above, an enterically
coated particle may have a diameter of about 30-1000 nm, as that
range is described herein. In certain embodiments an enterically
coated particle has a diameter of about 200-500 nm, as that range
is described herein. An enterically coated particle may comprise
any polymer described herein, such as a Eudragit.RTM. polymer
(e.g., Eudragit.RTM. L100 or Eudragit.RTM. S100). An enteric
coating may comprise, e.g., an acetylated monoglyceride, such as a
Myvacet.TM. distilled acetylated monoglyceride. Such acetylated
monoglycerides are known in the art, and include, e.g., Myvacet.TM.
9-45. Combinations of agents may be comprised within an enteric
coating of the present invention. For example, a Eudragit.RTM.
polymer and a Myvacet.TM. distilled acetylated monoglyceride may be
comprised in an enteric coating of an enterically coated particle
of the present invention. The mesh fraction of the enterically
coated particle may, in certain embodiments, range from about +40
to +90 mesh fraction (e.g., +40, +50, +60, +70, +80, +90, or any
range derivable therein).
[0016] Pharmaceutical compositions that comprise a particle of the
present invention are also described herein. Such pharmaceutical
compositions typically comprise at least one pharmaceutically
acceptable carrier. Particles of the present invention may be
comprised in a suspension and as such, the present invention
contemplates pharmaceutical compositions comprising a particle of
the present invention, wherein the particle is comprised in a
suspension. Any pharmaceutical composition that comprises a
particle may be further defined as an orally administerable
pharmaceutical composition. The orally administerable
pharmaceutical composition may, in certain embodiments, be
comprised in a suspension or capsule. The orally administerable
pharmaceutical composition may further comprise a flavoring agent.
A pharmaceutical composition that comprises a particle of the
present invention may be further defined as a time release
pharmaceutical composition, wherein the time release pharmaceutical
composition is formulated to release the opioid receptor antagonist
over time. Particles comprised in a pharmaceutical composition may
comprise any additive described herein, such as a polyanionic
additive (e.g., pentasodium tripolyphosphate). Another non-limiting
example of a pharmaceutical composition that comprises a particle
of the present invention is a pharmaceutical composition comprising
a plurality of heteroparticulate particles and at least one
pharmaceutical carrier, wherein the heteroparticulate particles
comprise: (a) an inner, larger particle comprising an opioid
receptor antagonist; and (b) a plurality of outer, smaller
particles comprising at least one surfactant and at least one
additive, wherein the average diameter of the outer particles is
between about 100-500 nm, as that range is described herein. In
certain embodiments, the range of the average diameter of the outer
particles is greater, such as between about 100-1000 nm.
[0017] Methods of making particles comprising an opioid receptor
antagonist are also contemplated. For example, certain embodiments
of the present invention contemplate a method of making one or more
particles wherein each particle comprises an opioid receptor
antagonist. The method may comprise, for example: (a) dissolving an
opioid receptor antagonist in water to form a dissolved opioid
receptor antagonist solution; (b) adding the dissolved opioid
receptor antagonist solution to a solution comprising a first
additive to form an opioid receptor antagonist/first additive
solution; and (c) adding the opioid receptor antagonist/first
additive solution to a solution comprising a second additive, such
that the plurality of particles is made. Such methods may further
comprise, e.g., stirring of the solution comprising the second
additive as the dissolved opioid receptor antagonist/first additive
solution is added. In certain embodiments, such methods further
comprise (d) centrifuging the suspension such that liquid therein
is separated from the particles comprising the opioid receptor
antagonist; (e) removing the supernatant; and (e) lyophilizing the
particles. Such methods may further comprise encapsulating the
particles in an enteric coating. Enteric coatings are described
herein. The opioid receptor antagonist may be any opioid receptor
antagonist described herein.
[0018] As noted herein, a particle of the present invention that
comprises an opioid receptor antagonist may be a heteroparticulate
particle. The present invention contemplates a heteroparticulate
particle comprising: (a) an inner, optionally larger or optionally
smaller particle comprising an opioid receptor antagonist; and (b)
an outer, optionally smaller or optionally larger particle. The
heteroparticulate particle may comprise at least one surfactant
and/or at least one additive, as those terms are described herein.
The diameter of a heteroparticulate particle may range from 30-1000
nm or higher, as that range is described herein. In certain
embodiments, a heteroparticulate particle has a diameter of the
outer particle that is between about 100-500 nm, as that range is
described herein. In certain embodiments, a heteroparticulate
particle has a diameter of the outer particle that is between about
100-1000 nm. The inner, larger particle may be further defined as a
microparticle. The inner particle may be a nanoparticle. The inner,
larger particle of part (a) may further comprise a loading agent.
Loading agents are described herein. A loading agent may comprise,
e.g., SiO.sub.2. The loading agent may be further defined as, e.g.,
Aerosil.RTM. 200. In certain embodiments, the inner, larger
particle comprises a core of the opioid receptor antagonist coated
by a plurality of outer particles. In certain embodiments, the
outer particles in a heteroparticulate particle comprise an opioid
receptor antagonist. In certain embodiments, one or more outer,
smaller particles of a heteroparticulate particle is formulated as
an enteric coating.
[0019] Any particle of the present invention may comprise a
surfactant. Surfactants are described herein. For example, a
surfactant may comprise a phosphatidylcholine. Phosphatidylcholines
are described herein. A surfactant may be, for example, Epikuron
170.RTM.. A surfactant may be a nonionic surfactant, such as
Tween.RTM. 80.
[0020] Any particle of the present invention may comprise a
time-release agent. Time-release agents are described herein. In
certain embodiments, the outer, smaller particle of a
heteroparticulate particle is formulated with a time-release agent
that permits release of an opioid receptor antagonist over time.
Such a time-release agent may be, e.g., a poly(caprolactone).
[0021] Another general aspect of the present invention contemplates
a heteroparticulate particle comprising: (a) an inner phase
comprising one larger particle, wherein the larger particle
comprises an opioid receptor antagonist and a loading agent; and
(b) an outer phase comprising a plurality of smaller particles,
wherein each smaller particle comprises Epikuron 170.RTM.,
Tween.RTM. 80, a poly(caprolactone) polymer and/or a Eudragit.RTM.
polymer.
[0022] Also contemplated are methods of making a heteroparticulate
particle comprising an opioid receptor antagonist. Such methods may
comprise, for example, (a) preparing an aqueous suspension
comprising a plurality of first particles; (b) dispersing at least
one second particle comprising an opioid receptor antagonist into
the aqueous suspension comprising a plurality of first particles;
and (c) spray-drying the product of step (b), wherein the diameter
of the second particle is larger than the average diameter of the
plurality of first particles. Such methods may further comprise,
e.g., concentrating the aqueous suspension comprising a plurality
of first particles. The aqueous suspension comprising a plurality
of first particles may comprise: (a) at least two surfactants,
wherein one surfactant is dissolved in an aqueous solution; (b) at
least two additives, and (c) an organic solvent. In certain
embodiments, the average diameter of the plurality of outer
particles is about 100-500 nm, as that range is described herein.
In certain embodiments, the average diameter of the plurality of
outer particles is about 100-1000 nm.
[0023] Methods of administering particles of the present invention
are also contemplated, and such methods are described herein. For
example, a method comprising administering a particle comprising an
opioid receptor antagonist and at least one additive to a patient,
wherein the particle is either (a) a particle having a diameter of
about 30-1000 nm, as that range is described herein; or (b) a
heteroparticulate particle having an inner particle and an outer
particle, wherein the inner particle comprises the opioid receptor
antagonist and wherein the diameter of the outer particle is about
100-500 nm, as that range is described herein, is contemplated. In
certain embodiments, the diameter of the outer particle is greater,
such as between about 100-1000 nm. Any particle of the present
invention may be employed in such methods. As discussed herein,
such administration may be, e.g., orally, intraadiposally,
intraarterially, intraarticularly, intradermally, intralesionally,
intramuscularly, intranasally, intraocularally, intraperitoneally,
intrapleurally, intrarectally, intrathecally, intratracheally,
intraumbilically, intravenously, intravesicularly, intravitreally,
liposomally, locally, mucosally, parenterally, rectally,
subconjunctival, subcutaneously, sublingually, topically,
transbuccally, transdermally, in creams, in lipid compositions, via
a catheter, via a lavage, via continuous infusion, via infusion,
via inhalation, via injection, via local delivery, via localized
perfusion, bathing target cells directly, or any combination
thereof. In particular embodiments, the administration is orally,
intravenously, or via injection. The outer particles of the
heteroparticulate particle may be further defined as a plurality of
outer particles. The particle may be formulated to release the
opioid receptor antagonist over time.
[0024] Patients or subjects of any appropriate method described
herein are described below. For example, a patient may be suffering
from or may be at risk of suffering from constipation, dysphoria,
pruritus, or urinary retention. In certain embodiments, the patient
is suffering from or is at risk of suffering a disorder selected
from ileus, post-operative ileus, paralytic ileus, post-partum
ileus, gastrointestinal dysfunction developing following abdominal
surgery, and idiopathic constipation. In certain embodiments, the
patient is suffering from a disorder mediated by opioid receptor
activity selected from cancer involving angiogenesis, an
inflammatory disorder, immune suppression, a cardiovascular
disorder, chronic inflammation, chronic pain, sickle cell anemia, a
vascular wound, retinopathy, decreased biliary secretion, decreased
pancreatic secretion, biliary spasm, and increased gastroesophageal
reflux.
[0025] In particular embodiments, the present invention
contemplates a method comprising administering to a patient a
particle comprising at least one opioid receptor antagonist and
chitosan.
[0026] Other general aspects of the present invention contemplate a
method for preventing an opioid-induced side effect in a patient
comprising orally administering an effective amount of a particle
of the present invention, such as an enterically coated particle,
comprising an opioid receptor antagonist and at least one additive
to the patient prior to administration of an opioid, wherein, for
example, the enterically coated particle is either (a) a particle
having a diameter of about 30-1000 nm, as that range is described
herein; or (b) a heteroparticulate particle having an inner
particle and a plurality of outer particles, wherein the inner
particle comprises the opioid receptor antagonist and wherein the
outer particles each comprise an enteric agent and the average
diameter of the outer particles is about 100-500 nm, as that range
is described herein. In certain embodiments, the range of the
average diameter of the outer particles is greater, such as between
about 100-1000 nm. The opioid induced side effect may comprise, for
example, at least one effect selected from inhibition of intestinal
motility, gastrointestinal dysfunction, constipation, bowel
hypomotility, impaction, gastric hypomotility, inhibition of
gastric motility, inhibition of gastric emptying, delayed gastric
emptying, incomplete evacuation, nausea, emesis, cutaneous
flushing, bloating, abdominal distension, sweating, dysphoria,
pruritis, and urinary retention. In certain embodiments, the
effective amount of the enterically coated particle comprising an
opioid receptor antagonist is less than the effective amount of an
aqueous solution of the opioid receptor antagonist. In certain
embodiments, the effective amount of the particle, such as an
enterically coated particle, comprising an opioid receptor
antagonist is less than the effective amount of an enterically
coated opioid receptor antagonist that is not comprised in an
enterically coated particle. In certain embodiments, the effective
amount of the enterically coated opioid receptor antagonist that is
not comprised in a particle is further defined as either: (a) an
effective amount of an enterically coated opioid receptor
antagonist that is not comprised in a particle having a size of
about 30-1000 nm, as that range is described herein; or (b) an
effective amount of an enterically coated opioid receptor
antagonist that is not comprised in a heteroparticulate particle
having an inner particle and a plurality of outer particles,
wherein the inner particle comprises the opioid receptor antagonist
and wherein the outer particles each comprise an enteric agent and
the average diameter of the outer particles is about 100-500 nm. In
certain embodiments, the range of the average diameter of the outer
particles is greater, such as between about 100-1000 nm.
[0027] Dosages of particles of the present invention are described
herein. In certain embodiments of any method described herein, the
dosage of a particle comprising an opioid receptor antagonist, such
as an enterically coated particle, is about 0.1-10 mg/kg body
weight, as that range is described herein.
[0028] Also contemplated are methods for treating an opioid induced
side effect comprising administering, e.g., orally administering,
an effective amount of a particle, such as an enterically coated
particle, comprising an opioid receptor antagonist to a patient
subsequent to administration of an opioid. The particle may be, for
example, either (a) a particle having a diameter of about 30-1000
nm, as that range is described herein; or (b) a heteroparticulate
particle having an inner particle and a plurality of outer
particles, wherein the inner particle comprises the opioid receptor
antagonist and wherein the outer particles each comprise an enteric
agent and the average diameter of the outer particles is about
100-500 nm, as that range is described herein. In certain
embodiments, the range of the average diameter of the outer
particles is greater, such as between about 100-1000 nm. In certain
embodiments, the effective amount of the enterically coated
particle comprising an opioid receptor antagonist is less than the
effective amount of an aqueous solution of the opioid receptor
antagonist. In certain embodiments, the effective amount of the
enterically coated particle comprising an opioid receptor
antagonist is less than the effective amount of an enterically
coated opioid receptor antagonist that is not comprised in a
particle.
[0029] Methods for treating gastrointestinal dysfunction following
abdominal surgery comprising administering a particle of the
present invention to a patient are contemplated, such as methods
comprising orally administering an effective amount of an
enterically coated particle comprising an opioid receptor
antagonist to a patient, wherein the dysfunction is treated,
wherein the particle is either: (a) a particle having a diameter of
about 30-1000 nm, as that range is described herein; or (b) a
heteroparticulate particle having an inner particle and a plurality
of outer particles, wherein the inner particle comprises the opioid
receptor antagonist and wherein the outer particles each comprise
an enteric agent and the average diameter of the outer particles is
about 100-500 nm, as that range is described herein. In certain
embodiments, the range of the average diameter of the outer
particles is greater, such as between about 100-1000 nm.
[0030] Methods for preventing inhibition of gastrointestinal
motility in a patient are also contemplated, such as methods for
preventing inhibition of gastrointestinal motility in a patient
prior to the patient receiving an opioid for pain resulting from
surgery comprising administering an effective amount of a particle
of the present invention, such as an enterically coated particle,
comprising an opioid receptor antagonist to the patient, wherein
the particle is either (a) a particle having a diameter of about
30-1000 nm, as that range is described herein; or (b) a
heteroparticulate particle having an inner particle and a plurality
of outer particles, wherein the inner particle comprises the opioid
receptor antagonist and wherein the outer particles each comprise
an enteric agent and the average diameter of the outer particles is
about 100-500 nm, as that range is described herein. In certain
embodiments, the range of the average diameter of the outer
particles is greater, such as between about 100-1000 nm.
[0031] Another general aspect of the present invention contemplates
a method for treating inhibition of gastrointestinal motility in a
patient receiving an opioid for pain resulting from surgery
comprising administering an effective amount of a particle of the
present invention, such as an enterically coated particle,
comprising an opioid receptor antagonist to the patient. The
particle may be, for example, either: (a) a particle having a
diameter of about 30-1000 nm, as that range is described herein; or
(b) a heteroparticulate particle having an inner particle and a
plurality of outer particles, wherein the inner particle comprises
the opioid receptor antagonist and wherein the outer particles each
comprise an enteric agent and the average diameter of the outer
particles is about 100-500 nm, as that range is described herein.
In certain embodiments, the range of the average diameter of the
outer particles is greater, such as between about 100-1000 nm.
[0032] Also contemplated are methods of preventing or treating an
opioid-induced side effect in a chronic opioid patient, comprising
administering an effective amount of a particle of the present
invention, such as an enterically coated particle comprising an
opioid receptor antagonist, to the patient. The particle may be,
for example, either: (a) a particle having a diameter of about
30-1000 nm, as that range is described herein; or (b) a
heteroparticulate particle having an inner particle and a plurality
of outer particles, wherein the inner particle comprises the opioid
receptor antagonist and wherein the outer particles each comprise
an enteric agent and the average diameter of the outer particles is
about 100-500 nm, as that range is described herein. The side
effect may be, for example, inhibition of intestinal motility,
gastrointestinal dysfunction, constipation, bowel hypomotility,
impaction, gastric hypomotility, inhibition of gastric motility,
inhibition of gastric emptying, delayed gastric emptying,
incomplete evacuation, nausea, emesis, cutaneous flushing,
bloating, abdominal distension, sweating, dysphoria, pruritis, or
urinary retention.
[0033] In certain embodiments, following administration of a
particle comprising an opioid receptor antagonist, the opioid
receptor antagonist is not substantially released in the stomach.
As used herein, "the opioid receptor antagonist is not
substantially released in the stomach" refers to a method wherein
less than 10% of the administered opioid receptor antagonist is
released in the stomach. The reduced drug absorption by the stomach
may be measured using any technique known in the art, such as by
drug plasma level analysis using, e.g., HPLC, such as C.sub.max,
T.sub.max, and AUC (area under the curve). See, e.g., Yuan et al.,
1997 and Yuan et al., 2000.
[0034] Any embodiment discussed with respect to one aspect of the
invention applies to other aspects of the invention as well.
[0035] The embodiments in the Example section are understood to be
embodiments of the invention that are applicable to all aspects of
the invention.
[0036] The term "effective," as that term is used in the
specification and/or claims, means adequate to accomplish a
desired, expected, or intended result.
[0037] "Therapeutically effective amount" means that amount which,
when administered to a subject for treating a condition, disease,
or side effect, is sufficient to effect such treatment for the
condition, disease, or side effect.
[0038] "Treatment" or "treating" includes: (1) inhibiting a
condition, disease, or side effect in a subject or patient
experiencing or displaying the pathology or symptomatology of the
condition, disease, or side effect (e.g., arresting further
development of the pathology and/or symptomatology), (2)
ameliorating a condition, disease, or side effect in a subject or
patient that is experiencing or displaying the pathology or
symptomatology of the condition, disease, or side effect (e.g.,
reversing the pathology and/or symptomatology), and/or (3)
effecting any measurable decrease in a condition, disease, or side
effect in a subject or patient that is experiencing or displaying
the pathology or symptomatology of the condition, disease, or side
effect.
[0039] "Prevention" or "preventing" includes: (1) inhibiting the
onset of a condition, disease, or side effect in a subject or
patient who may be at risk and/or predisposed to the condition,
disease, or side effect but does not yet experience or display any
or all of the pathology or symptomatology of the condition,
disease, or side effect, and/or (2) slowing the onset of the
pathology or symptomatology of the condition, disease, or side
effect in a subject or patient which may be at risk and/or
predisposed to the condition, disease, or side effect but does not
yet experience or display any or all of the pathology or
symptomatology of the condition, disease, or side effect.
[0040] As used herein, the term "patient" or "subject" refers to a
living mammalian organism, such as a human, monkey, cow, sheep,
goat, dog, cat, mouse, rat, guinea pig, or transgenic species
thereof. Non-limiting examples of human subjects are adults,
juveniles, children, infants and fetuses.
[0041] In certain embodiments, a patient is a chronic opioid user.
Accordingly, aspects of the invention are useful to prevent or
reduce the occurrence or reoccurrence of an opioid-induced side
effect in a chronic opioid patient. A chronic opioid patient may be
any of the following: a cancer patient, an AIDS patient, or any
other terminally ill patient. A chronic opioid patient may be a
patient taking methadone. Chronic opioid use is characterized by
the need for substantially higher levels of opioid to produce the
therapeutic benefit as a result of prior opioid use, as is well
known in the art. Chronic opioid use is also characterized by the
need for substantially lower levels of opioid antagonist to produce
the therapeutic benefit. Chronic opioid use as used herein includes
daily opioid treatment for a week or more or intermittent opioid
use for at least two weeks. In one embodiment, a patient, such as a
chronic opioid user, is taking a laxative and/or a stool
softener.
[0042] "Pharmaceutically acceptable" means that which is useful in
preparing a pharmaceutical composition that is generally safe,
non-toxic and neither biologically nor otherwise undesirable and
includes that which is acceptable for veterinary use as well as
human pharmaceutical use.
[0043] "Pharmaceutically acceptable salts" means salts of compounds
of the present invention which are pharmaceutically acceptable, as
defined above, and which possess the desired pharmacological
activity. Accordingly, pharmaceutically acceptable salts of
compounds of the present invention are contemplated herein. Such
pharmaceutically acceptable salts include acid addition salts
formed with inorganic acids such as hydrochloric acid, hydrobromic
acid, sulfuric acid, nitric acid, phosphoric acid, and the like; or
with organic acids such as 1,2-ethanedisulfonic acid,
2-hydroxyethanesulfonic acid, 2-naphthalenesulfonic acid, 3
-phenylpropionic acid, 4,4'-methylenebis(3 -hydroxy-2-ene-1-carb
oxylicacid), 4-methylbicyclo[2.2.2]oct-2-ene-1-carboxylic acid,
acetic acid, aliphatic mono- and dicarboxylicacids, aliphatic
sulfuric acids, aromatic sulfuric acids, benzenesulfonic acid,
benzoic acid, camphorsulfonic acid, carbonic acid, cinnamic acid,
citric acid, cyclopentanepropionic acid, ethanesulfonic acid,
fumaric acid, glucoheptonic acid, gluconic acid, glutamic acid,
glycolic acid, heptanoic acid, hexanoic acid, hydroxynaphthoic
acid, lactic acid, laurylsulfuric acid, maleic acid, malic acid,
malonic acid, mandelic acid, methanesulfonic acid, muconic acid,
o-(4-hydroxybenzoyl)benzoic acid, oxalic acid,
p-chlorobenzenesulfonic acid, phenyl-substituted alkanoic acids,
propionic acid, p-toluenesulfonic acid, pyruvic acid, salicylic
acid, stearic acid, succinic acid, tartaric acid,
tertiarybutylacetic acid, trimethylacetic acid, and the like.
Pharmaceutically acceptable salts also include base addition salts
which may be formed when acidic protons present are capable of
reacting with inorganic or organic bases. Acceptable inorganic
bases include sodium hydroxide, sodium carbonate, potassium
hydroxide, aluminum hydroxide and calcium hydroxide. Acceptable
organic bases include ethanolamine, diethanolamine,
triethanolamine, tromethamine, N-methylglucamine and the like. It
should be recognized that the particular anion or cation forming a
part of any salt of this invention is not critical, so long as the
salt, as a whole, is pharmacologically acceptable. Additional
examples of pharmaceutically acceptable salts and their methods of
preparation and use are presented in Handbook of Pharmaceutical
Salts: Properties, Selection and Use (P. H. Stahl & C. G.
Wermuth eds., Verlag Helvetica Chimica Acta, 2002), which is
incorporated herein by reference.
[0044] It is contemplated that any embodiment discussed in this
specification can be implemented with respect to any method or
composition of the invention, and vice versa. Furthermore,
compositions of the invention can be used to achieve methods of the
invention.
[0045] It is also contemplated that any method described herein may
be described using Swiss-type use language.
[0046] The use of the term "or" in the claims is used to mean
"and/or" unless explicitly indicated to refer to alternatives only
or the alternatives are mutually exclusive.
[0047] Throughout this application, the term "about" is used to
indicate that a value includes the standard deviation of error for
the device or method being employed to determine the value.
[0048] Following long-standing patent law, the words "a" and "an,"
when used in conjunction with the word "comprising" in the claims
or specification, denotes one or more, unless specifically
noted.
[0049] The terms "comprise," "have" and "include" are open-ended
linking verbs. Any forms or tenses of one or more of these verbs,
such as "comprises," "comprising," "has," "having," "includes" and
"including," are also open-ended. For example, any method that
"comprises," "has" or "includes" one or more steps is not limited
to possessing only those one or more steps and also covers other
unlisted steps.
[0050] Other objects, features and advantages of the present
invention will become apparent from the following detailed
description. It should be understood, however, that the detailed
description and the specific examples, while indicating specific
embodiments of the invention, are given by way of illustration
only, since various changes and modifications within the spirit and
scope of the invention will become apparent to those skilled in the
art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] The following drawings form part of the present
specification and are included to further demonstrate certain
aspects of the present invention. The invention may be better
understood by reference to one or more of these drawings in
combination with the detailed description of specific embodiments
presented herein.
[0052] FIG. 1 shows methylnaltrexone (MNTX) plasma levels at the
indicated times after oral administration of MNTX, N1-MNTX, and
N2-MNTX to rats.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
Opioid Receptor Antagonists
[0053] The opioid receptor antagonists of the present invention
include both centrally and peripherally acting opioid receptor
antagonists. In certain embodiments, peripherally acting opioid
receptor antagonists are contemplated.
[0054] Opioid receptor antagonists form a class of compounds that
can vary in structure while maintaining their antagonist
properties. These compounds include tertiary and quaternary
morphinans, such as noroxymorphone derivatives; N-substituted
piperidines, such as piperidine-N-alkylcarboxylates, tertiary and
quaternary benzomorphans, and tertiary and quaternary normorphinan
derivatives, such as 6-carboxy-normorphinan derivatives. Tertiary
compound antagonists are fairly lipid soluble and cross the
blood-brain barrier easily. Examples of opioid receptor antagonists
that cross the blood-brain barrier and are centrally (and
peripherally) active include, e.g., naloxone, naltrexone (each of
which is commercially available from Baxter Pharmaceutical
Products, Inc.), and nalmefene (available, e.g., from DuPont
Pharma). Peripherally restricted antagonists, on the other hand,
are typically charged, polar, and/or of high molecular weight:
these properties typically impede their crossing the blood-brain
barrier. Methylnaltrexone is a quaternary derivative of the
tertiary opioid receptor antagonist, naltrexone. Addition of the
methyl group to naltrexone forms a compound with greater polarity
and lower lipid solubility. Thus, methylnaltrexone does not cross
the blood-brain barrier and has the potential for blocking the
undesired adverse effects which are typically mediated by
peripherally located receptors.
[0055] A peripheral opioid receptor antagonist suitable for use in
the invention may be a compound which is a quaternary morphinan
derivative, such as a quaternary noroxymorphone of formula (I):
##STR00001##
wherein R is alkyl, alkenyl, alkynyl, aryl, cycloalkyl-substituted
alkyl, or arylsubstituted alkyl, and X.sup.- is the anion, such as
a chloride, bromide, iodide, or methylsulfate anion. The
noroxymorphone derivatives of formula (I) can be prepared, for
example, according to the procedure in U.S. Pat. No. 4,176,186,
which is incorporated herein by reference; see also U.S. Pat. Nos.
4,719,215; 4,861,781; 5,102,887; 5,972,954; and 6,274,591; U.S.
Patent Application Nos. 2002/0028825 and 2003/0022909; and PCT
publication Nos. WO 99/22737 and WO 98/25613, all of which are
hereby incorporated by reference.
[0056] A compound of formula (I) may be N-methylnaltrexone (or
simply methylnaltrexone), wherein R is cyclopropylmethyl as
represented in formula (II):
##STR00002##
wherein X.sup.- may be any pharmaceutically acceptable anion.
Methylnaltrexone is a quaternary derivative of the .mu.-opioid
receptor antagonist naltrexone. Methylnaltrexone exists as a salt
(e.g., N-methylnaltrexone bromide) and the terms "methylnaltrexone"
or "MNTX", as used herein, therefore embrace such salts.
"Methylnaltrexone" or "MNTX" thus specifically includes, but is not
limited to, bromide salts, chloride salts, iodide salts, carbonate
salts, and sulfate salts of methylnaltrexone. Names used for the
bromide salt of MNTX in the literature, for example, include:
methylnaltrexone bromide; N-methylnaltrexone bromide; naltrexone
methobromide; naltrexone methyl bromide; SC-37359; MRZ-2663-BR; and
N-cyclopropylmethylnoroxy-morphine-methobromide. A compound of
formula (I) may be S-N-methylnaltrexone.
[0057] Methylnaltrexone is commercially available from, e.g.,
Mallinckrodt Pharmaceuticals, St. Louis, Mo. Methylnaltrexone is
provided as a white crystalline powder, freely soluble in water,
typically as the bromide salt. The compound as provided is 99.4%
pure by reverse phase HPLC, and contains less than 0.011%
unquaternized naltrexone by the same method. Methylnaltrexone can
be prepared as a sterile solution at a concentration of, e.g.,
about 5 mg/M1
[0058] Other suitable peripheral opioid receptor antagonists may
include N-substituted piperidines, such as
piperidine-N-alkylcarboxylates as represented by formula (III):
##STR00003##
wherein R.sup.1 is hydrogen or alkyl; R.sup.2 is hydrogen, alkyl,
or alkenyl; R.sup.3 is hydrogen, alkyl, alkenyl, aryl, cycloalkyl,
cycloalkenyl, cycloalkyl-substituted alkyl,
cycloalkenyl-substituted alkyl, or aryl-substituted alkyl; R.sup.4
is hydrogen, alkyl, or alkenyl; A is OR.sup.5 or NR.sup.6R.sup.7;
wherein R.sup.5 is hydrogen, alkyl, alkenyl, cycloalkyl,
cycloalkenyl, cycloalkyl-substituted alkyl,
cycloalkenyl-substituted alkyl, or aryl-substituted alkyl; R.sup.6
is hydrogen or alkyl; R.sup.7 is hydrogen, alkyl, alkenyl, aryl,
cycloalkyl, cycloalkenyl, cycloalkyl-substituted alkyl,
cycloalkenyl-substituted alkyl or aryl-substituted alkyl, or
alkylene-substituted B or together with the nitrogen atom to which
they are attached, R.sup.6 and R.sup.7 form a heterocyclic ring
selected from pyrrole and piperidine; B is
##STR00004##
wherein R.sup.8 is hydrogen or alkyl; R.sup.9 is hydrogen, alkyl,
alkenyl, aryl, cycloalkyl, cycloalkenyl, cycloalkyl-substituted
alkyl, cycloalkenyl-substituted alkyl or aryl-substituted alkyl or
together with the nitrogen atom to which they are attached, R.sup.8
and R.sup.9 form a heterocyclic ring selected from pyrrole and
piperidine; W is OR.sup.10, NR.sup.11R.sup.12, or OE; wherein
R.sup.10 is hydrogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl,
cycloalkyl-substituted alkyl, cycloalkenyl-substituted alkenyl, or
aryl-substituted alkyl; R.sup.11 is hydrogen or alkyl; R.sup.12 is
hydrogen, alkyl, alkenyl, aryl, cycloalkyl, cycloalkenyl,
cycloalkyl-substituted alkyl, cycloalkenyl-substituted alkyl,
aryl-substituted alkyl, or alkylene-substituted C(.dbd.O)Y or,
together with the nitrogen atom to which they are attached,
R.sup.11 and R.sup.12 form a heterocyclic ring selected from
pyrrole and piperidine; E is
##STR00005##
alkylene-substituted (C.dbd.O)D, or --R.sup.13OC(.dbd.O)R.sup.14;
wherein R.sup.13 is alkyl-substituted alkylene; R.sup.14 is alkyl;
D is OR.sup.15 or NR.sup.16R.sup.17; wherein R.sup.15 is hydrogen,
alkyl, alkenyl, cycloalkyl, cycloalkenyl, cycloalkyl-substituted
alkyl, cycloalkenyl substituted alkyl, or aryl-substituted alkyl;
R.sup.16 is hydrogen, alkyl, alkenyl, aryl, aryl-substituted alkyl,
cycloalkyl, cycloalkenyl, cycloalkyl substituted alkyl, or
cycloalkenyl-substituted alkyl; R.sup.17 is hydrogen or alkyl or,
together with the nitrogen atom to which they are attached, R.sup.6
and R.sup.17 form a heterocyclic ring selected from the group
consisting of pyrrole or piperidine; Y is OR.sup.18 or
NR.sup.19R.sup.20 ; wherein R.sup.18 is hydrogen, alkyl, alkenyl,
cycloalkyl, cycloalkenyl, cycloalkyl-substituted alkyl,
cycloalkenyl-substituted alkyl, or aryl-substituted alkyl; R.sup.19
is hydrogen or alkyl; R.sup.20 is hydrogen, alkyl, alkenyl, aryl,
cycloalkyl, cycloalkenyl, cycloalkyl-substituted alkyl,
cycloalkenyl-substituted alkyl, or aryl-substituted alkyl or,
together with the nitrogen atom to which they are attached,
R.sup.19 and R.sup.20 form a heterocyclic ring selected from
pyrrole and piperidine; R.sup.21 is hydrogen or alkyl; and n is 0
to 4.
[0059] Non-limiting examples of suitable N-substituted piperidines
may be prepared as disclosed in U.S. Pat. Nos. 5,270,328;
6,451,806; and 6,469,030, all of which are hereby incorporated by
reference. Such compounds have moderately high molecular weights, a
zwitterionic form, and a polarity that prevent penetration of the
blood-brain barrier.
[0060] Particular piperidine-N-alkylcarbonylates include
N-alkylamino-3,4,4-substituted piperidines, such as alvimopan
represented below as formula (IV):
##STR00006##
Alvimopan is available from Adolor Corp., Exton, Pa.
[0061] Still other suitable peripheral opioid receptor antagonist
compounds may include quaternary benzomorphan compounds. Quaternary
benzomorphan compounds may have the following formula (V):
##STR00007##
wherein R.sup.1 is hydrogen, acyl, or acetoxy; and R.sup.2 is alkyl
or alkenyl; R is alkyl, alkenyl, or alkynyl and X.sup.31 is an
anion, such as a chloride, bromide, iodide, or methylsulfate
anion.
[0062] Specific quaternary derivatives of benzomorphan compounds
that may be employed in the methods of the invention include the
following compounds of formula (V):
2'-hydroxy-5,9-dimethyl-2,2-diallyl-6,7-b enzom orphanium-bromide;
2'-hydroxy-5,9-dimethyl-2-n-propyl-2-allyl-6,7-benzomorphanium-bromide;
2'-hydroxy-5, 9-dimethyl-2-n-propyl-2-prop
argyl-6,7-benzomorphanium-bromide; and
2'-acetoxy-5,9-dimethyl-2-n-propyl-2-allyl-6,7-benzomorphanium-bromide.
[0063] Other quaternary benzomorphan compounds that may be employed
in methods of the invention are described, for example, in U.S.
Pat. No. 3,723,440, the entire disclosure of which is incorporated
herein by reference.
[0064] Other peripheral opioid antagonists include
6-carboxy-normorphinan derivatives, particularly
N-methyl-C-normorphinan derivatives, as described in U.S. Published
Application No. 2008/0064744, hereby incorporated in its entirety
herein by reference, and including the compound having the
following formula (VI):
##STR00008##
[0065] Other peripheral opioid antagonists may include polymer
conjugates of opioid antagonists, as described in U.S. Published
Application No. 2006/0105046, hereby incorporated by reference.
Specific polymer conjugates include PEGylated naloxone and
naltrexone.
[0066] The invention also encompasses administration of more than
one opioid receptor antagonist. Any combination of opioid receptor
antagonists is contemplated, including combinations of .mu.-opioid
receptor antagonists and combinations of .mu.- and
.kappa.-antagonists: for example, a combination of methylnaltrexone
and alvimopan.
II. Particles of the Present Invention
[0067] Particles of the present invention comprise at least one
opioid receptor antagonist. Certain properties of particles of the
present invention are discussed below.
A. Properties of Particles
[0068] As noted above, a particle may comprise only one type of
particle ("homoparticulate"), or a particle may comprise two or
more types of particles ("heteroparticulate"). Accordingly, the
term "particle" encompasses both homo- and heteroparticulate
particles. A "type" of particle refers to a particle comprising a
particular set of ingredients. Thus, two different types of
particles will have two different sets of ingredients (e.g., one
particle comprises an opioid receptor antagonist and one particle
does not). If two particles contain the same ingredients but the
ratio of ingredients differs, the two particles are still
considered to be of the same "type."
[0069] A particle may comprise two or more particles and still be a
homoparticulate particle, wherein the two or more particles are of
the same type. For example, if a particle comprises two particles
having different sizes, but the ingredients of each particle is the
same, then the particle is a homoparticulate particle. If a
particle comprises two or more particles and the two or more
particles are of different types, then the particle is a
heteroparticulate particle regardless of the sizes of the
particles. In any case, the two or more particles may be in
physical contact with each other such that the particles are found
together as a unit, wherein that unit is also considered a
particle.
[0070] In certain embodiments, a particle may comprise a single
particle. In certain embodiments, a particle may comprise two or
more particles. Accordingly, the term "particle" encompasses
particles having only one particle, and particles having two or
more particles. Regarding particles comprising two or more
particles, there may be an inner particle and an outer particle.
For example, an inner particle may be in physical contact with one
or more particles that are found on the surface of the inner
particle such that they are "outer" particles. In certain
embodiments, a plurality of outer particles coat the inner
particle. As used herein, "coat" refers to where a plurality of
outer particles are found on about, at most about, or at least
about 90% of the surface of the inner particle. In certain
embodiments, "coat" refers to where a plurality of outer particles
are found on about, at most about, or at least about 90%, 95%, 99%,
or more, of the surface of the inner particle, or any range
derivable therein.
[0071] Generally speaking, then, any particle may be either a
homoparticulate particle or a heteroparticulate particle; any
particle may comprise only one particle, wherein that particle may
be either a homoparticulate particle or a heteroparticulate
particle; or any particle may comprise two or more particles,
wherein each of the two or more particles may be homoparticulate
particles or heteroparticulate particles, or a combination
thereof.
[0072] The following schematic demonstrates non-limiting
representations of cross-sections of particles of the present
invention, wherein each individual circle represents a particle,
and each of A-S represents a particle, and each particle may be the
same type or may be different types. These representations are not
to scale and are merely for illustrative purposes. The particles
are not necessarily spherical.
##STR00009## ##STR00010##
[0073] The diameters discussed herein apply to any type of particle
described herein, unless specifically noted otherwise. For example,
a homoparticulate particle, a heteroparticulate particle, or the
particles that make up a homoparticulate particle or a
heteroparticulate particle may each have a diameter as discussed
herein or, in the case of a plurality of particles, the plurality
may have an average diameter of the values discussed herein. Any
plurality of particles, as used herein, may all have about the same
size diameter, or may together have an average diameter size.
[0074] In certain embodiments, the diameter of a particle of the
present invention (or the average diameter of a plurality of
particles) is about 30-1000 nm. In certain embodiments, the
diameter is about, at most about, or at least about 30, 35, 40, 45,
50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140,
150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270,
280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400,
410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530,
540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650, 660,
670, 680, 690, 700, 710, 720, 730, 740, 750, 760, 770, 780, 790,
800, 810, 820, 830, 840, 850, 860, 870, 880, 890, 900, 910, 920,
930, 940, 950, 960, 970, 980, 990 or 1000 nm or higher, or any
range derivable therein. In certain embodiments, a particle's
diameter is less than 300 .mu.m, or less than about 300 .mu.m. In
certain embodiments, a diameter is less than, or less than about
300, 275, 250, 200, 150, 100, 75, 50, 10, 1, 0.75, 0.50, 0.25, 0.1,
0.01, or 0.001 .mu.m, or any range derivable therein. In certain
embodiments, a particle's diameter is less than 300 .mu.m, or less
than about 300 .mu.m, and greater than 1 nm (e.g., less than, or
less than about 300, 200, 100, 75, 50, 25, 10, 1, 0.1, or 0.010
.mu.m and greater than about 1 nm, or any range derivable therein).
When a plurality of such particles is employed, the average
diameter of the plurality of particles may be any of the values
discussed in this paragraph.
[0075] In certain embodiments, a particle may comprise an outer
particle that is found on the surface of an inner particle.
Typically, a plurality of outer particles are found on the surface
and in some embodiments, a plurality of outer particles coat an
individual inner particle. In certain embodiments, the inner and
outer particles comprise the same ingredients, such that the
particle is a homoparticulate particle. In certain embodiments, the
inner particle comprises different ingredients than the outer
particle, such that the particle is a heteroparticulate particle.
In certain embodiments, the inner and/or outer particle(s) is
further defined as a microparticle or a nanoparticle (defined
below). In certain embodiments, a particle may comprise a smaller,
outer particle that is found on the surface of an individual
larger, inner particle and typically, a plurality of smaller
particles coat the individual larger, inner particle. In certain
embodiments, the diameter of the outer particle ranges from about,
at most about, or at least about 100-500 nm. For example, the
diameter of the outer particle may be about, at least about, or at
most about 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350,
375, 400, 425, 450, 475, 500 nm, or any range derivable therein. In
other embodiments, the range of the diameter of the outer particle
may be larger, such as about, at least about, or at most about 100,
125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425,
450, 475, 500, 525, 550, 575, 600, 625, 650, 675, 700, 725, 750,
775, 800, 825, 850, 875, 900, 925, 950, 975 or 1000 nm, or any
range derivable therein. In certain embodiments wherein a plurality
of outer, smaller particles coat an inner, larger particle, the
average diameter of the plurality of outer, smaller particles
ranges between about 100-500 nm, as this range is described above.
In certain embodiments, a larger, outer particle is found on the
surface of an individual smaller, inner particle. In certain
embodiments, a plurality of larger particles are found on the
surface of an individual smaller, inner particle. In certain
embodiments, a plurality of larger particles coat the surface of an
individual inner, smaller particle, wherein the meaning of "coat"
is as described above.
[0076] In certain embodiments, particles of the present invention
are microparticles. A microparticle is defined as a particle having
a diameter of about 0.1-100 .mu.m. In certain embodiments, the
diameter of a microparticle is about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6,
0.7. 0.8, 0.9, 1, 1.5, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50,
55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 .mu.m, or any range
derivable therein. In certain embodiments, a particle comprises
only one microparticle. In certain embodiments, a particle
comprises or contains only a plurality of microparticles. In
certain embodiments, a microparticle may be comprised in a
homoparticulate particle. In certain embodiments, a microparticle
may be comprised in a heteroparticulate particle. In certain
embodiments, at least one particle having a smaller diameter than
the microparticle is found on the surface of the microparticle. In
certain embodiments, a plurality of smaller, outer particles coat
the microparticle. In certain embodiments, one or more larger,
outer particles coat the microparticle.
[0077] In certain embodiments, particles of the present invention
are nanoparticles. A nanoparticle is defined as a particle having a
diameter of about 1-100 nm. In certain embodiments, the diameter of
a nanoparticle is about 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45,
50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 nm, or any range
derivable therein. In certain embodiments, a particle comprises
only one nanoparticle. In certain embodiments, a particle comprises
or contains only a plurality of nanoparticles. In certain
embodiments, a nanoparticle may be comprised in a homoparticulate
particle. In certain embodiments, a nanoparticle may be comprised
in a heteroparticulate particle. In certain embodiments, a
plurality of nanoparticles coat an inner particle. In certain
embodiments, a plurality of smaller, outer nanoparticles coat a
larger, inner particle. In certain embodiments, the inner particle
of a homo- or heteroparticulate particle is a nanoparticle;
further, in certain embodiments, one or more larger or smaller
particles may be found on the surface of such a nanoparticle. For
example, a plurality of larger or smaller particles may coat the
surface of a nanoparticle.
[0078] Particle diameters may also span the diameters described for
micro- and nanoparticles (e.g., about 30-1000 nm, as that range is
described herein).
B. Additives
[0079] A variety of additives may be employed in the particles of
the present invention. Additives may be characterized in more than
one fashion. In certain embodiments polymeric additives may be
employed. In certain embodiments, polysaccharides may be employed.
Homopolysaccharides and/or heteropolysaccharides are contemplated,
as well as a variety of molecular weights (e.g., 10,000-150,000
g/mol). Non-limiting examples of polysaccharides include chitosan
and cellulose (e.g., microcrystalline cellulose). Hydrophobic
additives may be employed, in certain embodiments. A hydrophobic
additive is defined as an additive having a surface energy that is
less than 40 dynes/cm. Non-limiting examples of hydrophobic
additives include methacrylic acid copolymer, sodium carboxymethyl
cellulose, cellulose acetate, ethyl cellulose (EC), hydroxypropyl
methyl-cellulose acetate succinate (HPMCAS) and cellulose acetate
phthalate (CAP). Hydrophilic additives are also contemplated, in
certain embodiments. A hydrophilic additive is defined as an
additive having a surface energy of .gtoreq.40 dynes/cm. Certain
hydrophilic additives are positively charged at acidic and neutral
pH, and certain hydrophilic additives are negatively charged at
acidic and neutral pH. Non-limiting examples of hydrophilic
additives include, for example, chitosan and/or polyphosphates such
as tripolyphosphate (e.g., pentasodium tripolyphosphate, TPP).
Hydrophilic additives may also be either polycationic and/or
polyanionic. An example of a polyanionic additive is a
polyphosphate, such as TPP. Yet another example of a polyanionic
additive is dextran sulfate (Sarmento et al., 2007).
[0080] When more than one additive is present in a particle, the
ratio of the additives in the particle may vary widely. For
example, the ratio of one additive to any other additive in a
particle may range from 1:1 to 1:100,000 w/w. In certain
embodiments, the w/w ratio is 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:4,
1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:25, 1:50, 1:100, 1:250, 1:500,
1:750, 1:1000, 1:1500, 1:2000, 1:2500, 1:3000, 1:3500, 1:4000,
1:4500, 1:5000, 1:5500, 1:6000, 1:6500, 1:7000, 1:7500, 1:8000;
1:8500; 1:9000, 1:9500, 1:10,000, 1:25,000, 1:50,000, 1:75,000 or
1:100,000, or any range derivable therein. In certain embodiments,
the ratio is 1:1. In certain embodiments, the ratio is 1:10 w/w.
For example, where two additives are present in a particle, the
ratio between the two additives may range from 1:1 to 1:100,000, or
any range derivable therein, as that range is described above.
Where three additives are present, A, B and C, the w/w/w ratios of
A:B:C may range from 1:1:1 to 1:100,000:1 to 1:100,000:100,000 to
100,000:1:1, to 100,000:100,000:1 to 100,000:1:100,000, to
1:1:100,000, or any range derivable therein, as that range is
described above. In certain embodiments, the ratio is 1:1:10 w/w/w.
When four or more additives are comprised within a particle of the
present invention, the ratios may be adjusted similarly.
[0081] Further, when more than one additive is present in a
particle, any combination of additives discussed herein may be
employed. For example, a polysaccharide and a hydrophobic additive
may be employed. A polysaccharide and a hydrophilic additive may be
employed. A hydrophobic additive and a hydrophilic additive may be
employed. A polycationic and/or a polyanionic additive may be
combined with each other or with any other additive described
herein. The ratios of these additives may be any ratio as described
herein. Further, an additive may be combined with one or more
surfactants, enteric agents, time-release agents, or loading
agents, as described herein.
[0082] The ratio of additive to opioid receptor antagonist may also
vary widely. For example, the ratio may range from 9:4 to 9:32
additive:antagonist (w/w). The range may be broader, such as from
9:1 to 9:128 w/w. In certain embodiments, the w/w ratio is
1.8:3.2.
[0083] Surfactants may also be employed in certain particles of the
present invention. Surfactants are well-known in the art.
Non-limiting examples of surfactants include nonionic, cationic and
anionic surfactants. In particular embodiments, nonionic
surfactants are contemplated, such as Tween.RTM. 80. Other nonionic
Tween.RTM. products are also contemplated. In certain embodiments,
phosphatidylcholine surfactants may be employed, such as Epikuron
170.RTM.. Phosphatidylcholines, including those obtained from egg,
soy beans, or other plant sources or those that are partially or
wholly synthetic, or of variable lipid chain length and
unsaturation, are suitable for use in the present invention.
Synthetic, semisynthetic and natural product phosphatidylcholines
including, but not limited to, distearoylphosphatidylcholine
(DSPC), hydrogenated soy phosphatidylcholine (HSPC), soy
phosphatidylcholine (soy PC), egg phosphatidylcholine (egg PC),
dioleoylphosphatidylcholine (DOPC), hydrogenated egg
phosphatidylcholine (HEPC), dielaidoylphosphatidylcholine (DEPC),
dipalmitoylphosphatidylcholine (DPPC) and
dimyristoylphosphatidylcholine (DMPC) are suitable
phosphatidylcholines for use in this invention. All of these agents
are commercially available. Combinations of surfactants may also be
used. Moreover, any surfactant discussed herein may be combined
with any one or more additive, polymer, or enteric, time-release,
or loading agent, as discussed throughout this application.
C. Enteric, Time-Release and Loading Agents
[0084] Any particle of the present invention may be enterically
coated. Enteric coatings prevent or inhibit release of medication
before the medication reaches the small intestine. In particular,
enteric coatings preferentially dissolve in conditions having a
higher pH than the acidic pH of the stomach, which typically has a
pH of less than about 3.0 (e.g., less than about 3.0, 2.5, 2.0,
1.5, or 1, or any range derivable therein). For example, an enteric
coating may dissolve or partially dissolve in a pH of about 3.5,
4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5 or higher, or any
range derivable therein.
[0085] Agents for enteric coatings are well-known in the art, and
include methacrylic acid copolymers, cellulose acetate, styrol
maleic acid copolymers, hydroxypropylmethyl cellulose acetate and
shellac. Other polymers that may be used for enteric coating
purposes include Eudragits.RTM., such as anionic Eudragit.RTM.
copolymers (e.g., Eudragit.RTM. L100 and Eudragit.RTM. S100).
Enteric coatings may also comprise other agents, such as an
acetylated monoglyceride, such as Myvacet.RTM. distilled acetylated
monoglyceride (e.g., Myvacet 5-07, 7-07, 9-08 and 9-45).
Combinations of any enteric agents known in the art, including
those described below, are also contemplated. Enteric agents may be
combined with one or more additives, polymers, surfactants,
time-release agents, and/or loading agents, as described herein. An
enteric coating need not coat the entire particle of an enterically
coated particle: in certain embodiments, an enteric coating coats
at least about 90%, 95%, 99% or 100% of the particle. In certain
embodiments, an enteric coating coats 100% of the particle.
[0086] Suitable enteric coatings are also described, for example,
in U.S. Pat. Nos. 4,311,833; 4,377,568; 4,457,907; 4,462,839;
4,518,433; 4,556,552; 4,606,909; 4,615,885; 4,670,287; 5,536,507;
5,567,423; 5,591,433; 5,597,564; 5,609,871; 5,614,222; 5,626,875;
and 5,629,001, all of which are incorporated herein by
reference.
[0087] Other exemplary enteric agents include alkyl and
hydroxyalkyl celluloses and their aliphatic esters, e.g.,
methylcellulose, ethylcellulose, hydroxyethylcellulose,
hydroxypropylcellulose, hydroxybutylcellulose,
hydroxyethylethylcellulose, hydroxyprophymethylcellulose,
hydroxybutylmethylcellulose, hydroxypropylcellulose phthalate,
hydroxypropylmethylcellulose phthalate and
hydroxypropylmethylcellulose acetate succinate;
carboxyalkylcelluloses and their salts, e.g.,
carboxymethylethylcellulose; cellulose acetate phthalate; cellulose
acetate trimellitate, polycarboxymethylene and its salts and
derivatives; polyvinyl alcohol and its esters (e.g., polyvinyl
acetate phthalate); polycarboxymethylene copolymer with sodium
formaldehyde carboxylate; acrylic polymers and copolymers, e.g.,
methacrylic acid-methyl methacrylic acid copolymer and methacrylic
acid-methyl acrylate copolymer; edible oils such as peanut oil,
palm oil, olive oil and hydrogenated vegetable oils;
polyvinylpyrrolidone; polyethylene glycol and its esters; and
natural products such as shellac, and zein.
[0088] Other enteric agents include polyvinylacetate esters, e.g.,
polyvinyl acetate phthalate; alkyleneglycolether esters of
copolymers such as partial ethylene glycol monomethylether ester of
ethylacrylate-maleic anhydride copolymer or diethyleneglycol
monomethylether ester of methylacrylate-maleic anhydride copolymer,
N-butylacrylate-maleic anhydride copolymer, isobutylacrylate-maleic
anhydride copolymer or ethylacrylate-maleic anhydride copolymer;
and polypeptides resistant to degradation in the gastric
environment, e.g., polyarginine and polylysine. Other suitable
agents and methods to make and use such formulations are well known
to those skilled in the art (see, e.g., Remington: The Science and
Practice of Pharmacy, 19th ed. (1995) Mack Publishing Company,
Easton, Pa.; herein incorporated by reference).
[0089] Certain particles of the present invention may be formulated
for time-release of an opioid receptor antagonist. Time-release
agents are well-known in the art, and such formulations may
comprise an additive, a polymer and/or an enteric agent,
surfactant, or loading agent. For example, poly(caprolactone) of a
variety of molecular weights (e.g., 30,000-90,000 g/mol) may be
employed for this purpose. Non-polymers may also be used, such as
tamsulosin, as described in U.S. Published Application No.
2008/0113030, incorporated herein by reference. Combinations of
time-release agents are also contemplated.
[0090] Loading agents may be employed to facilitate the making of
particles. For example, an opioid receptor antagonist may be
combined with a loading agent to produce a particle comprising the
antagonist and the loading agent, such that the particle is
"loaded" with the antagonist. Loading agents suitable for this
purpose are well-known in the art. For example, loading agents
comprising silica (SiO.sub.2) may be employed. Loading agents
comprising alkyl.sub.(C.ltoreq.5)-modified silica may also be used.
Such products are commercially available. Combinations of loading
agents are also contemplated. Moreover, loading agents may be
combined with one or more additives, polymers, surfactants, enteric
agents, or time-release agents.
III. Chemical Definitions
[0091] "Alkyl" refers to a univalent aliphatic hydrocarbon group
which is saturated and which may be straight, branched, or cyclic
having from 1 to about 10 carbon atoms in the chain, and all
combinations and subcombinations of chains therein. Exemplary alkyl
groups include, but are not limited to, methyl, ethyl, n-propyl,
isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl,
cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.
[0092] "Lower alkyl" refers to an alkyl group having 1 to about 6
carbon atoms.
[0093] "Alkenyl" refers to a univalent aliphatic hydrocarbon group
containing at least one carbon-carbon double bond and having from 2
to about 10 carbon atoms in the chain, and all combinations and
subcombinations of chains therein. Exemplary alkenyl groups
include, but are not limited to, vinyl, propenyl, butynyl,
pentenyl, hexenyl, and heptnyl.
[0094] "Alkynyl" refers to a univalent aliphatic hydrocarbon group
containing at least one carbon-carbon triple bond and having from 2
to about 10 carbon atoms in the chain, and combinations and
subcombinations of chains therein. Exemplary alkynyl groups
include, but are not limited to, ethynyl, propynyl, butynyl,
pentynyl, hexynyl, and heptynyl.
[0095] "Alkylene" refers to a divalent aliphatic hydrocarbon group
having from 1 to about 6 carbon atoms, and all combinations and
subcombinations of chains therein. The alkylene group may be
straight, branched, or cyclic. There may be optionally inserted
along the alkylene group one or more oxygen, sulfur, or optionally
substituted nitrogen atoms, wherein the nitrogen substituent is an
alkyl group as described previously.
[0096] "Alkenylene" refers to a divalent alkylene group containing
at least one carbon-carbon double bond, which may be straight,
branched, or cyclic. Exemplary alkenylene groups include, but are
not limited to, ethenylene (--CH.dbd.CH--) and propenylene
(--CH.dbd.CHCH.sub.2--).
[0097] "Cycloalkyl" refers to a saturated monocyclic or bicyclic
hydrocarbon ring having from about 3 to about 10 carbons, and all
combinations and subcombinations of rings therein. The cycloalkyl
group may be optionally substituted with one or more
cycloalkyl-group substituents. Exemplary cycloalkyl groups include,
but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl,
cyclohexyl, and cycloheptyl.
[0098] "Acyl" means an alkyl-CO group wherein alkyl is as
previously described. Exemplary acyl groups include, but are not
limited to, acetyl, propanoyl, 2-methylpropanoyl, butanoyl, and
palmitoyl.
[0099] "Aryl" refers to an aromatic carbocyclic radical containing
from about 6 to about 10 carbons, and all combinations and
subcombinations of rings therein. The aryl group may be optionally
substituted with one or two or more aryl group substituents.
Exemplary aryl groups include, but are not limited to, phenyl and
naphthyl.
[0100] "Aryl-substituted alkyl" refers to a linear alkyl group,
preferably a lower alkyl group, substituted at a terminal carbon
with an optionally substituted aryl group, preferably an optionally
substituted phenyl ring. Exemplary aryl-substituted alkyl groups
include, for example, phenylmethyl, phenylethyl, and
3(4-methylphenyl)propyl.
[0101] "Heterocyclic" refers to a monocyclic or multicyclic ring
system carbocyclic radical containing from about 4 to about 10
members, and all combinations and subcombinations of rings therein,
wherein one or more of the members of the ring is an element other
than carbon, for example, nitrogen, oxygen, or sulfur. The
heterocyclic group may be aromatic or nonaromatic. Exemplary
heterocyclic groups include, for example, pyrrole and piperidine
groups.
[0102] "Halo" refers to fluoro, chloro, bromo, or iodo.
[0103] Compounds employed in methods of the invention (e.g., opioid
receptor antagonists) may contain one or more
asymmetrically-substituted carbon or nitrogen atoms, and may be
isolated in optically active or racemic form. Thus, all chiral,
diastereomeric, racemic form, epimeric form, and all geometric
isomeric forms of a structure are intended, unless the specific
stereochemistry or isomeric form is specifically indicated.
Compounds may occur as racemates and racemic mixtures, single
enantiomers, diastereomeric mixtures and individual diastereomers.
In some embodiments, a single diastereomer is obtained. The chiral
centers of the compounds of the present invention can have the S-
or the R-configuration, as defined by the IUPAC 1974
Recommendations. Compounds may be of the D- or L- form, for
example. It is well known in the art how to prepare and isolate
such optically active forms. For example, mixtures of stereoisomers
may be separated by standard techniques including, but not limited
to, resolution of racemic form, normal, reverse-phase, and chiral
chromatography, preferential salt formation, recrystallization, and
the like, or by chiral synthesis either from chiral starting
materials or by deliberate synthesis of target chiral centers.
[0104] In addition, atoms making up the compounds of the present
invention are intended to include all isotopic forms of such atoms.
Isotopes, as used herein, include those atoms having the same
atomic number but different mass numbers. By way of general example
and without limitation, isotopes of hydrogen include tritium and
deuterium, and isotopes of carbon include .sup.13C and
.sup.14C.
[0105] Compounds of the invention also encompass their salts. The
term "salt(s)" as used herein, is understood as being acidic and/or
basic salts formed with inorganic and/or organic acids and bases.
Zwitterions (internal or inner salts) are understood as being
included within the term "salt(s)" as used herein, as are
quaternary ammonium salts, such as alkylammonium salts. Some
embodiments contemplate nontoxic, pharmaceutically acceptable salts
as described herein, although other salts may be useful, as, for
example, in isolation or purification steps. Salts include, but are
not limited to, sodium, lithium, potassium, amines, tartrates,
citrates, hydrohalides, phosphates and the like.
[0106] The compounds employed in methods of the invention may exist
in prodrug form. As used herein, "prodrug" is intended to include
any covalently bonded carriers which release the active parent drug
or compounds that are metabolized in vivo to an active drug or
other compounds employed in the methods of the invention in vivo
when such prodrug is administered to a subject. Since prodrugs are
known to enhance numerous desirable qualities of pharmaceuticals
(e.g., solubility, bioavailability, manufacturing, etc.), the
compounds employed in some methods of the invention may, if
desired, be delivered in prodrug form. Thus, the invention
contemplates prodrugs of compounds of the present invention as well
as methods of delivering prodrugs. Prodrugs of the compounds
employed in the invention may be prepared by modifying functional
groups present in the compound in such a way that the modifications
are cleaved, either in routine manipulation or in vivo, to the
parent compound.
[0107] Accordingly, prodrugs include, for example, compounds
described herein in which a hydroxy, amino, or carboxy group is
bonded to any group that, when the prodrug is administered to a
subject, cleaves to form a free hydroxyl, free amino, or carboxylic
acid, respectively. Other examples include, but are not limited to,
acetate, formate, and benzoate derivatives of alcohol and amine
functional groups; and alkyl, carbocyclic, aryl, and alkylaryl
esters such as methyl, ethyl, propyl, iso-propyl, butyl, isobutyl,
sec-butyl, tert-butyl, cyclopropyl, phenyl, benzyl, and phenethyl
esters, and the like.
IV. Methods of Administration and Other Formulation
Considerations
[0108] Pharmaceutical compositions of the present invention
comprise an effective amount of one or more candidate substances
(e.g., a particle of the present invention) or additional agents
dissolved or dispersed in a pharmaceutically acceptable carrier.
The preparation of a pharmaceutical composition that contains at
least one candidate substance or additional active ingredient will
be known to those of skill in the art in light of the present
disclosure, as exemplified by Remington's Pharmaceutical Sciences,
18th Ed. Mack Printing Company, 1990, incorporated herein by
reference. Moreover, for animal (e.g., human) administration, it
will be understood that preparations should meet sterility,
pyrogenicity, general safety and purity standards as required by
FDA Office of Biological Standards.
[0109] As used herein, "pharmaceutically acceptable carrier"
includes any and all solvents, dispersion media, coatings,
surfactants, antioxidants, preservatives (e.g., antibacterial
agents, antifungal agents), isotonic agents, absorption delaying
agents, salts, preservatives, drugs, drug stabilizers, gels,
binders, excipients, disintegration agents, lubricants, sweetening
agents, flavoring agents, dyes, such like materials and
combinations thereof, as would be known to one of ordinary skill in
the art (see, for example, Remington's Pharmaceutical Sciences, pp
1289-1329, 1990). Except insofar as any conventional carrier is
incompatible with the active ingredient, its use in the therapeutic
or pharmaceutical compositions is contemplated.
[0110] The candidate substance may comprise different types of
carriers depending on whether it is to be administered in solid,
liquid or aerosol form, and whether it needs to be sterile for such
routes of administration. Particles of the present invention may be
administered alone or as comprised in a composition (e.g., a
pharmaceutical composition) orally, intraadiposally,
intraarterially, intraarticularly, intracranially, intradermally,
intralesionally, intramuscularly, intranasally, intraocularally,
intrapericardially, intraperitoneally, intrapleurally,
intraprostaticaly, intrarectally, intrathecally, intratracheally,
intraumbilically, intravaginally, intravenously, intravesicularly,
intravitreally, liposomally, locally, mucosally, orally,
parenterally, rectally, subconjunctival, subcutaneously,
sublingually, topically, transbuccally, transdermally, vaginally,
in creams, in lipid compositions, via a catheter, via a lavage, via
continuous infusion, via infusion, via inhalation, via injection,
via local delivery, via localized perfusion, bathing target cells
directly, or by other method or any combination of the foregoing as
would be known to one of ordinary skill in the art (see, for
example, Remington's Pharmaceutical Sciences, 1990). In particular
embodiments, a particle of the present invention may be formulated
for oral delivery. In certain embodiments, intramuscular,
intravenous, topical administration, or inhalation administration
is contemplated. In certain embodiments, oral administration is
contemplated. As noted, pharmaceutical compositions comprising a
particle of the present invention are also contemplated, and such
compositions may be adapted for administration via any method known
to those of skill in the art, such as the methods described
above.
[0111] In particular embodiments, a particle of the present
invention or composition comprising such a particle is administered
to a subject using a drug delivery device. Any drug delivery device
is contemplated in this regard.
[0112] The actual dosage amount of an opioid receptor antagonist
comprised in a particle of the present invention that is
administered to a subject can be determined by physical and
physiological factors such as body weight, severity of condition,
the type of disease being treated, previous or concurrent
therapeutic interventions, idiopathy of the patient and on the
route of administration. The practitioner responsible for
administration will typically determine the concentration of active
ingredient(s) in a composition and appropriate dose(s) for the
individual subject.
[0113] The dose can be repeated as needed as determined by those of
ordinary skill in the art. Thus, in some embodiments of the methods
set forth herein, a single dose is contemplated. In other
embodiments, two or more doses are contemplated. Where more than
one dose is administered to a subject, the time interval between
doses can be any time interval as determined by those of ordinary
skill in the art. For example, the time interval between doses may
be about 1 hour to about 2 hours, about 2 hours to about 6 hours,
about 6 hours to about 10 hours, about 10 hours to about 24 hours,
about 1 day to about 2 days, about 1 week to about 2 weeks, or
longer, or any time interval derivable within any of these recited
ranges.
[0114] In certain embodiments, it may be desirable to provide a
continuous supply of a pharmaceutical composition to the patient.
This could be accomplished by catheterization, followed by
continuous administration of the therapeutic agent, for example.
The administration could be intra-operative or post-operative.
[0115] In certain embodiments, pharmaceutical compositions may
comprise, for example, at least about 0.1% of an opioid receptor
antagonist. In other embodiments, the opioid receptor antagonist
may comprise between about 2% to about 75% of the weight of the
unit, or between about 25% to about 60%, for example, and any range
derivable therein. In other non-limiting examples, a dose may also
comprise from about 10 .mu.g/kg/body weight, 100 .mu.g/kg/body
weight, 200 .mu.g/kg/body weight, 350 .mu.g/kg/body weight, 500
.mu.g/kg/body weight, 1 mg/kg/body weight, 5 mg/kg/body weight, 10
mg/kg/body weight, 50 mg/kg/body weight, to about 100 mg/kg/body
weight or more of the opioid receptor antagonist per
administration, or any range derivable therein. In a non-limiting
example of a derivable range from the numbers listed herein, a
range of about 0.1 mg/kg/body weight to about 10 mg/kg/body weight
may be administered.
[0116] In any case, the composition may comprise various
antioxidants to retard oxidation of one or more component.
Additionally, the prevention of the action of microorganisms can be
brought about by preservatives such as various antibacterial and
antifungal agents, including but not limited to parabens (e.g.,
methylparabens, propylparabens), chlorobutanol, phenol, sorbic
acid, thimerosal, or combinations thereof.
[0117] The opioid receptor antagonist comprised in a particle may
be formulated into a composition, such as a pharmaceutical
composition, in a free base, neutral, or salt form.
Pharmaceutically acceptable salts are described herein.
[0118] In embodiments wherein a carrier is employed, such a carrier
may be a solvent or dispersion medium comprising but not limited
to, water, ethanol, polyol (e.g., glycerol, propylene glycol,
liquid polyethylene glycol, etc.), lipids (e.g., triglycerides,
vegetable oils, liposomes) and combinations thereof. The proper
fluidity can be maintained, for example, by the use of a coating,
such as lecithin; by the maintenance of the required particle size
by dispersion in carriers such as, for example liquid polyol or
lipids; by the use of surfactants such as, for example
hydroxypropylcellulose; or combinations thereof such methods. It
may be preferable to include isotonic agents, such as, for example,
sugars, sodium chloride, or combinations thereof.
[0119] In other embodiments, one may use eye drops, nasal solutions
or sprays, aerosols or inhalants in the present invention. Such
compositions are generally designed to be compatible with the
target tissue type. In a non-limiting example, nasal solutions are
usually aqueous solutions designed to be administered to the nasal
passages in drops or sprays. Nasal solutions are prepared so that
they are similar in many respects to nasal secretions, so that
normal ciliary action is maintained. Thus, in certain embodiments
the aqueous nasal solutions usually are isotonic or slightly
buffered to maintain a pH of about 5.5 to about 6.5. In addition,
antimicrobial preservatives, similar to those used in ophthalmic
preparations, drugs, or appropriate drug stabilizers, if required,
may be included in the formulation. For example, various commercial
nasal preparations are known and include drugs such as antibiotics
or antihistamines.
[0120] In certain embodiments the candidate substance is prepared
for administration by such routes as oral ingestion. In these
embodiments, the solid composition may comprise, for example,
solutions, suspensions, emulsions, tablets, pills, capsules (e.g.,
hard or soft shelled gelatin capsules), sustained release
formulations, buccal compositions, troches, elixirs, suspensions,
syrups, wafers, or combinations thereof In particular embodiments,
suspensions and capsules are contemplated. Oral compositions may be
incorporated directly with the food of the diet. In certain
embodiments, carriers for oral administration comprise inert
diluents (e.g., glucose, lactose, or mannitol), assimilable edible
carriers or combinations thereof. In other aspects of the
invention, the oral composition may be prepared as a syrup or
elixir. A syrup or elixir, and may comprise, for example, at least
one active agent, a sweetening agent, a preservative, a flavoring
agent, a dye, a preservative, or combinations thereof.
[0121] In certain embodiments an oral composition may comprise one
or more binders, excipients, disintegration agents, lubricants,
flavoring agents, or combinations thereof. In certain embodiments,
a composition may comprise one or more of the following: a binder,
such as, for example, gum tragacanth, acacia, cornstarch, gelatin
or combinations thereof; an excipient, such as, for example,
dicalcium phosphate, mannitol, lactose, starch, magnesium stearate,
sodium saccharine, cellulose, magnesium carbonate or combinations
thereof; a disintegrating agent, such as, for example, corn starch,
potato starch, alginic acid or combinations thereof; a lubricant,
such as, for example, magnesium stearate; a sweetening agent, such
as, for example, sucrose, lactose, saccharin or combinations
thereof; a flavoring agent, such as, for example peppermint, oil of
wintergreen, cherry flavoring, orange flavoring, etc.; or
combinations thereof the foregoing. When the dosage unit form is a
capsule, it may contain, in addition to materials of the above
type, carriers such as a liquid carrier. Various other materials
may be present as coatings or to otherwise modify the physical form
of the dosage unit. For instance, tablets, pills, or capsules may
be coated with shellac, sugar, or both.
[0122] Sterile injectable solutions may be prepared by
incorporating a particle of the present invention in the required
amount in the appropriate solvent with various of the other
ingredients enumerated above, as required, followed by
sterilization. Generally, dispersions are prepared by incorporating
the various sterilized active ingredients into a sterile vehicle
which contains the basic dispersion medium and/or the other
ingredients. In the case of sterile powders for the preparation of
sterile injectable solutions, suspensions or emulsion, certain
methods of preparation may include vacuum-drying or freeze-drying
techniques which yield a powder of the active ingredient plus any
additional desired ingredient from a previously sterilized liquid
medium thereof. The liquid medium should be suitably buffered if
necessary and the liquid diluent (e.g., water) first rendered
isotonic prior to injection with sufficient saline or glucose. The
preparation of highly concentrated compositions for direct
injection is also contemplated, where the use of DMSO as solvent is
envisioned to result in extremely rapid penetration, delivering
high concentrations of the active agents to a small area.
[0123] The composition should be stable under the conditions of
manufacture and storage, and preserved against the contaminating
action of microorganisms, such as bacteria and fungi. It will be
appreciated that endotoxin contamination should be kept minimally
at a safe level, for example, less that 0.5 ng/mg protein.
[0124] In particular embodiments, prolonged absorption of an
injectable composition can be brought about by the use in the
compositions of agents delaying absorption, such as, for example,
aluminum monostearate, gelatin, or combinations thereof.
[0125] Certain embodiments of the present invention refer to
aqueous formulations or solutions of methylnaltrexone,
specifically. Such aqueous formulations may include a chelating
agent, a buffering agent, an anti-oxidant and, optionally, an
isotonicity agent, and may be pH adjusted to between about
3.0-3.5.
V. Combination Therapy
[0126] In order to enhance or increase the effectiveness of an
opioid receptor antagonist comprised in a particle of the present
invention, the particle may be combined with another therapy, such
as another agent that combats and/or prevents a disorder mediated
by opioid receptor activity. For example, a particle of the present
invention may be provided in a combined amount with an effective
amount of a second opioid receptor antagonist. Additionally, a
particle of the present invention may be provided in a combined
amount with an effective amount of an anti-cancer agent, as
described in U.S. Patent Application No. 2006/0258696, PCT
Publication No. WO 06/096626, or PCT Publication No. WO 07/053194,
all hereby incorporated by reference. The second agent may be
comprised in a second particle.
[0127] It is contemplated that combination therapy of the present
invention may be used in vitro or in vivo. These processes may
involve administering the agents at the same time or within a
period of time wherein separate administration of the substances
produces a desired therapeutic benefit. This may be achieved by
contacting the cell, tissue, or organism with a composition, such
as a pharmaceutically acceptable composition, that includes two or
more agents, or by contacting the cell with two or more distinct
compositions, wherein one composition includes one agent and the
other includes another.
[0128] The particles of the present invention may precede, be
co-current with and/or follow the other agents by intervals ranging
from minutes to weeks. In embodiments where the agents are applied
separately to a cell, tissue or organism, one would generally
ensure that a significant period of time did not expire between the
time of each delivery, such that the agents would still be able to
exert an advantageously combined effect on the cell, tissue or
organism. For example, in such instances, it is contemplated that
one may contact the cell, tissue or organism with two, three, four
or more modalities substantially simultaneously (i.e., within less
than about a minute) as the candidate substance. In other aspects,
one or more agents may be administered about 1 minute, 5 minutes,
10 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes, 2
hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9
hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours,
16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22
hours, 22 hours, 23 hours, 24 hours, 25 hours, 26 hours, 27 hours,
28 hours, 29 hours, 30 hours, 31 hours, 32 hours, 33 hours, 34
hours, 35 hours, 36 hours, 37 hours, 38 hours, 39 hours, 40 hours,
41 hours, 42 hours, 43 hours, 44 hours, 45 hours, 46 hours, 47
hours, 48 hours, 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, 7
days, 8 days, 9 days, 10 days, 11 days, 12 days, 13 days, 14 days,
15 days, 16 days, 17 days, 18 days, 19 days, 20 days, 21 days, 1,
2, 3, 4, 5, 6, 7 or 8 weeks or more, or any range derivable
therein, prior to and/or after administering the candidate
substance.
[0129] Various combination regimens of the agents may be employed.
Non-limiting examples of such combinations are shown below, wherein
a particle of the present invention is "A" and a second agent, such
as a second opioid receptor antagonist, is "B":
TABLE-US-00001 A/B/A B/A/B B/B/A A/A/B A/B/B B/A/A A/B/B/B B/A/B/B
B/B/B/A B/B/A/B A/A/B/B A/B/A/B A/B/B/A B/B/A/A B/A/B/A B/A/A/B
A/A/A/B B/A/A/A A/B/A/A A/A/B/A
VI. Examples
[0130] The following examples are included to demonstrate preferred
embodiments of the invention. It should be appreciated by those of
skill in the art that the techniques disclosed in the examples
which follow represent techniques discovered by the inventor to
function well in the practice of the invention, and thus can be
considered to constitute preferred modes for its practice. However,
those of skill in the art should, in light of the present
disclosure, appreciate that many changes can be made in the
specific embodiments which are disclosed and still obtain a like or
similar result without departing from the spirit and scope of the
invention.
[0131] Reagents used in each of these examples are commercially
available.
EXAMPLE 1
Preparation of Particles Comprising Methylnaltrexone
[0132] A procedure developed by the Alonso lab from the School of
Pharmacy, University of Santiago de Compostela, Spain was employed
(Calvo et al., 1997; Fernandez-Urrusuno et al., 1999).
[0133] Methylnaltrexone (MNTX) (Mallinckrodt Chemicals, St. Louis,
Mo.) was dissolved in water and then incorporated in an aqueous
pentasodium tripolyphosphate (TPP) solution. Under high-speed
magnetic stirring of an aqueous chitosan solution, the
MNTX-containing TPP solution was slowly added into the chitosan
solution. Nanoparticles containing MNTX were then formed. The final
ratio of chitosan:TPP:MNTX was approximately 5/1.8/3.2 (w/w/w).
MNTX nanoparticles were collected by centrifugation, supernatants
were discarded and the remaining nanoparticles were
lyophilized.
EXAMPLE 2
Preparation of Enterically Coated Particles Comprising
Methylnaltrexone
[0134] Enterically coated MNTX nanoparticles were prepared by
encapsulating the nanoparticles of Example 1 with a Eudagrit.RTM.
L100 and Myvacet.RTM. 9-45 mixture. See, e.g., U.S. Pat. No.
6,608,075 and Yuan et al., 2000, each of which is incorporated
herein by reference in its entirety. The final substance was the
30-80 mesh fraction which was 60% MNTX nanoparticles by weight. It
was shown to decrease release of the drug at gastric pH by 90%
based on the methods of the United States Pharmacopoeia/National
Formulary (The United States Pharmacopeia, 1995). See also U.S.
Pat. No. 6,608,075 and Yuan et al., 2000.
EXAMPLE 3
Preparation of A Heteroparticulate Particle Comprising
Methylnaltrexone
[0135] Methodology as described by Beck et al., 2004 was followed.
To prepare the outer particles, a lipophilic solution consisting of
Epikuron 170.RTM. (0.1532 g), a polymer (poly(caprolactone) (PCL)
(MW=60,000 g/mol) or Eudragit.RTM. S100) (1.0 g) and acetone (267.0
ml) was used. This organic phase was added to an aqueous solution
(533.0 ml) containing Tween 80.RTM. (0.1532 g) under moderate
magnetic stirring. The solution was concentrated by evaporation
under reduced pressure, and then the final volume was adjusted to
100 ml using acetone, corresponding to a polymer concentration of
10 mg/ml.
[0136] To prepare the inner particle, an MNTX solution (17 mM, 50
mL) was added to Aerosil.RTM. 200 (1.50 g). The mixture was fed
into a mini-spray-dryer to produce particles having an MNTX core
(feed rate: 3.0 ml/min; air flow rate: 500 NL/hr; atomizing air
pressure: 200 kPa; inlet temperature: 170.+-.4.degree. C.; outlet
temperature: 110.+-.4.degree. C.; nozzle diameter 0.7 mm).
[0137] The coating step was performed as follows: the MNTX
particles (1.5 g) were rapidly dispersed into the outer particle
suspension (50 mL) under magnetic stirring. This mixture was
spray-dried to obtain heteroparticulate particles, wherein the
inner particle comprised MNTX and the outer particles that
surrounded the inner particle comprised a polymer suitable as an
enteric coating (spray dryer conditions: feed rate: 3.0 ml/min; air
flow rate: 500 NL/hr; atomizing air pressure: 200 kPa; inlet
temperature: 170.+-.4.degree. C.; outlet temperature:
110.+-.4.degree. C.; nozzle diameter 0.7 mm).
[0138] This nanoparticles is pH-responsive. At pH 2.0 (in the
gastric environment), the drug release was very low. At pH 7.4, the
drug release was almost 100% in 15 min (The United States
Pharmacopeia, 1995).
EXAMPLE 4
In Vivo Study of Plasma Levels Upon Particle Administration
[0139] Abbreviations: N1-MNTX=particles of Example 2;
N2-MNTX=particles of Example 3 using PCL.
[0140] Male Wistar strain rats, weighing between 200-300 g were
used. Rats in group 1 (n=6) received 10 mg/kg regular MNTX (in
distilled water); rats in group 2 (n =7) received 10 mg/kg N1-MNTX
(in distilled water); rats in group 3 (n=5) received 10 mg/kg
N2-MNTX (in solution with pH 2). Drugs were administered orally via
a gavage tube in the morning at time 0. There were 6-8 rats per
group.
[0141] Blood samples were collected from the tail vein for the
measurement of plasma MNTX levels. The samples were typically
collected every 30 min. from time 0 to time 360 min. Plasma MNTX
levels were determined by high performance liquid chromatography
(HPLC) adapted from a previously reported method (Osinski et al.,
2002). The practical limit of detection for plasma samples was
approximately 2 ng/mL (100 pg/injection).
[0142] MNTX plasma levels after oral administration of MNTX,
N1-MNTX and N2-MNTX to rats are shown in FIG. 1. Absorption of MNTX
in both of the MNTX particle formulations (N1-MNTX and N2-MNTX)
into the blood stream of rats was much more efficient than the
absorption of aqueous MNTX. The chitosan/TPP/MNTX formulation
(N1-MNTX) proved to be more efficient than the Epikuron 170.RTM.
formulation (N2-MNTX), however both performed much better than
non-particulate MNTX. These results demonstrate that particle
formulations of methylnaltrexone and other opioid antagonists can
greatly increase the absorption of these compounds into the central
nervous system of mammals, thus decreasing the dose required to
reach therapeutic plasma levels.
REFERENCES
[0143] The following references, to the extent that they provide
exemplary procedural or other details supplementary to those set
forth herein, are specifically incorporated herein by
reference.
[0144] U.S. Pat. No. 3,723,440
[0145] U.S. Pat. No. 4,176,186
[0146] U.S. Pat. No. 4,311,833
[0147] U.S. Pat. No. 4,377,568
[0148] U.S. Pat. No. 4,457,907
[0149] U.S. Pat. No. 4,462,839
[0150] U.S. Pat. No. 4,518,433
[0151] U.S. Pat. No. 4,556,552
[0152] U.S. Pat. No. 4,606,909
[0153] U.S. Pat. No. 4,615,885
[0154] U.S. Pat. No. 4,670,287
[0155] U.S. Pat. No. 4,719,215
[0156] U.S. Pat. No. 4,861,781
[0157] U.S. Pat. No. 5,102,887
[0158] U.S. Pat. No. 5,270,328
[0159] U.S. Pat. No. 5,536,507
[0160] U.S. Pat. No. 5,567,423
[0161] U.S. Pat. No. 5,591,433
[0162] U.S. Pat. No. 5,597,564
[0163] U.S. Pat. No. 5,609,871
[0164] U.S. Pat. No. 5,614,222
[0165] U.S. Pat. No. 5,626,875
[0166] U.S. Pat. No. 5,629,001
[0167] U.S. Pat. No. 5,972,954
[0168] U.S. Pat. No. 6,274,591
[0169] U.S. Pat. No. 6,451,806
[0170] U.S. Pat. No. 6,469,030
[0171] U.S. Pat. No. 6,608,075
[0172] U.S. Published Appl. 2002/0028825
[0173] U.S. Published Appl. 2003/0022909
[0174] U.S. Published Appl. 2006/0105046
[0175] U.S. Published Appl. 2006/0258696
[0176] U.S. Published Appl. 2008/0064744
[0177] U.S. Published Appl. 2008/0113030
[0178] Beck et al., J Microencapsulation, 21:499-512, 2004.
[0179] Calvo et al., J Appl Pol Sci., 63:125-32, 1997.
[0180] Fernandez-Urrusuno et al., Pharm Res., 16:1576-81, 1999.
[0181] Handbook of Pharmaceutical Salts: Properties, Selection and
Use (Stahl and Wermuth, Eds.), Verlag Helvetica Chimica Acta,
2002.
[0182] Osinski et al., J Chromatogr B, 780:251-9, 2002.
[0183] PCT Appln. WO 06/096626
[0184] PCT Appln. WO 07/053194
[0185] PCT Appln. WO 98/25613
[0186] PCT Appln. WO 99/22737
[0187] Remington's: The Science and Practice of Pharmacy, 19.sup.th
Ed., Mac Publishing Co., Easton, Pa., 1676-1692, 1995.
[0188] Remington's Pharmaceutical Sciences, 18th Ed. Mack Printing
Company, 1289-1329, 1990.
[0189] Sarmento et al., Biomacromolecules, 8:3054-60, 2007.
[0190] The United States Pharmacopeia: The National Formulary.
Rockville: United States
[0191] Pharmacopeial Convention, Inc, 1793-1799, 1995.
[0192] Yuan et al., Clin. Pharmacol. Ther., 61:467-475, 1997
[0193] Yuan et al., Clin. Pharmacol. Ther., 67:398-404, 2000.
* * * * *