U.S. patent application number 10/665735 was filed with the patent office on 2005-09-01 for method of preventing abuse of opioid dosage forms.
Invention is credited to Colucci, Robert D., Kaiko, Robert F., Palermo, Philip J..
Application Number | 20050192309 10/665735 |
Document ID | / |
Family ID | 22082844 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050192309 |
Kind Code |
A1 |
Palermo, Philip J. ; et
al. |
September 1, 2005 |
Method of preventing abuse of opioid dosage forms
Abstract
The invention relates in part to a method of reducing the abuse
potential of an oral dosage form of an opioid analgesic, wherein an
analgesically effective amount of an orally active opioid agonist
is combined with an opioid antagonist into an oral dosage form
which would require at least a two-step extraction process to be
separated from the opioid agonist, the amount of opioid antagonist
including being sufficient to counteract opioid effects if
extracted together with the opioid agonist and administered
parenterally.
Inventors: |
Palermo, Philip J.; (Bethel,
CT) ; Colucci, Robert D.; (Newtown, CT) ;
Kaiko, Robert F.; (Weston, CT) |
Correspondence
Address: |
DAVIDSON, DAVIDSON & KAPPEL, LLC
14th Floor
485 Seventh Avenue
New York
NY
10018
US
|
Family ID: |
22082844 |
Appl. No.: |
10/665735 |
Filed: |
September 18, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10665735 |
Sep 18, 2003 |
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09815162 |
Mar 22, 2001 |
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6627635 |
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09815162 |
Mar 22, 2001 |
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09218663 |
Dec 22, 1998 |
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6228863 |
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60068479 |
Dec 22, 1997 |
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Current U.S.
Class: |
514/282 |
Current CPC
Class: |
A61P 25/34 20180101;
A61K 31/485 20130101; A61K 31/44 20130101; A61P 25/04 20180101;
Y10S 514/812 20130101; Y10S 514/81 20130101; A61P 25/36 20180101;
A61K 31/485 20130101; A61K 31/485 20130101; A61K 31/44 20130101;
A61K 2300/00 20130101; A61K 31/485 20130101; A61K 2300/00
20130101 |
Class at
Publication: |
514/282 |
International
Class: |
A61K 031/485 |
Claims
1-11. (canceled)
12. An oral dosage form comprising: (i) an analgesically effective
amount of an orally active opioid agonist; and (ii) naltrexone or a
pharmaceutically acceptable salt thereof; said opioid agonist and
naltrexone or pharmaceutically acceptable salt thereof being chosen
such that the opioid agonist and the naltrexone or pharmaceutically
acceptable salt thereof are only extractable from the dosage form
together, and at least a two-step extraction process is required to
separate the opioid antagonist from the naltrexone or
pharmaceutically acceptable salt thereof, the amount of naltrexone
or pharmaceutically acceptable salt thereof included being
sufficient to counteract opioid effects if extracted from the oral
dosage form together with the opioid agonist and administered
parenterally.
13. The oral dosage form of claim 12, wherein the opioid agonist is
hydromorphone hydrochloride and the naltrexone or pharmaceutically
acceptable salt thereof is naltrexone hydrochloride.
14. The oral dosage form of claim 12, wherein the opioid agonist is
oxycodone hydrochloride and the naltrexone or pharmaceutically
acceptable salt thereof is naltrexone hydrochloride.
15. The oral dosage form of claim 12, wherein the opioid agonist is
morphine sulfate and the naltrexone or pharmaceutically acceptable
salt thereof is naltrexone hydrochloride.
16. The oral dosage form of claim 12, wherein the opioid agonist is
hydrocodone bitartrate and the naltrexone or pharmaceutically
acceptable salt thereof is naltrexone hydrochloride.
17. The oral dosage form of claim 12, wherein the opioid agonist is
hydromorphone hydrochloride and the ratio of said naltrexone to
said hydromorphone is from about 0.148:1 to about 1.185:1 by
weight.
18. The oral dosage form of claim 12, wherein the opioid agonist is
hydromorphone hydrochloride and the ratio of said naltrexone to
said hydromorphone is from about 0.222:1 to about 0.111:1 by
weight.
19. The oral dosage form of claim 12, wherein the opioid agonist is
morphine sulfate and the ratio of said naltrexone to said morphine
is from about 0.018:1 to about 1.148:1 by weight.
20. The oral dosage form of claim 12, wherein the opioid agonist is
oxycodone hydrochloride and the ratio of said naltrexone to said
oxycodone is from about 0.037:1 to about 0.296:1 by weight.
21. The oral dosage form of claim 12, wherein the opioid agonist is
oxycodone hydrochloride and the ratio of said naltrexone to said
oxycodone is from about 0.056:1 to about 0.222:1 by weight.
22. The oral dosage form of claim 12, wherein the opioid agonist is
hydrocodone bitartrate and the ratio of said naltrexone to said
hydrocodone is from about 0.03:1 to about 0.27:1 by weight.
23. The oral dosage form of claim 12, further comprising a
sustained release carrier, wherein the sustained release carrier
provides for a release of said opioid agonist such that the dosage
form is suitable for administration on a twice-a-day or a
once-a-day basis.
Description
[0001] This application is a continuation application of U.S.
Provisional Application Ser. No. 60/068,479 filed Dec. 22, 1997,
hereby incorporated by reference.
[0002] Opioids, also known as opioid agonists, are a group of drugs
that exhibit opium or morphine-like properties. The opioids are
employed primarily as moderate to strong analgesics, but have many
other pharmacological effects as well, including drowsiness,
respiratory depression, changes in mood and mental clouding without
a resulting loss of consciousness. Opioids act as agonists,
interacting with stereospecific and saturable binding sites in the
brain and other tissues. Endogenous opioid-like peptides are
present particularly in areas of the central nervous system that
are presumed to be related to the perception of pain; to movement,
mood and behavior, and to the regulation of neuroendocrinological
functions. Opium contains more than twenty distinct alkaloids.
Morphine, codeine and papaverine are included in this group.
[0003] By the middle of the nineteenth century, the use of pure
alkaloids such as morphine rather than crude opium preparations
began to spread throughout the medical world. Parenteral use of
morphine tended to produce a more severe variety of compulsive drug
use. The problem of addiction to opioids stimulated a search for
potent analgesics that would be free of the potential to produce
addiction. By 1967, researchers had concluded that the complex
interactions among morphine-like drugs, antagonists, and what was
then called "mixed agonist-antagonist" could best be explained by
postulating the existence of more than one type of receptor for
opioids and related drugs. With the advent of new totally synthetic
entities with morphine-like actions, the term "opioid" was
generally retained as a generic designation for all exogenous
substances that bind stereo-specifically to any of several
subspecies of opioid receptors and produce agonist actions.
[0004] The potential for the development of tolerance and physical
dependence with repeated opioid use is a characteristic feature of
all the opioid drugs, and the possibility of developing
psychological dependence (i.e., addiction) is one of the major
concerns in the use of the treatment of pain with opioids, even
though iatrogenic addiction is rare. Another major concern
associated with the use of opioids is the diversion of these drugs
from the patient in pain to another (non-patient) for recreational
purposes, e.g., to an addict.
[0005] The overall abuse potential of an opioid is not established
by any one single factor. Instead, there is a composite of factors,
including, the capacity of the drug to produce the kind of physical
dependence in which drug withdrawal causes sufficient distress to
bring about drug-seeking behavior; the ability to suppress
withdrawal symptoms caused by withdrawal from other agents; the
degree to which it induces euphoria similar to that produced by
morphine and other opioids; the patterns of toxicity that occur
when the drug is dosed above its normal therapeutic range; and
physical characteristics of the drugs such as water solubility.
Such physical characteristics may determine whether the drug is
likely to be abused by the parenteral route.
[0006] In the United States, the effort to control the compulsive
drug user includes efforts to control drug availability by placing
restrictions on the use of opioids in the treatment of pain of
compulsive drug users. In practice, the physician is often faced
with a choice of administering potent opioid analgesics even to
persons who seem predisposed to develop psychological dependence,
i.e., addiction, on such drugs. In view of this problem, it has
been recommended that these patients should not be given an opioid
when another drug without a potential for abuse will suffice; and
further that these patients should not be permitted to
self-administer such drugs parenterally and should only be given a
few days' supply at a time.
[0007] At least three basic patterns of opioid use and dependence
have been identified. The first involves individuals whose drug use
begins in the context of medical treatment and who obtain their
initial supplies through, e.g., physicians. Another pattern begins
with experimental or "recreational" drug use and progresses to more
intensive use. A third pattern involves users who begin in one or
another of the preceding ways but later switch to oral opioids such
as methadone, obtained from organized addiction treatment
programs.
[0008] Tolerance refers to the need to increase the dose of opioid
over a period of time in order to achieve the same level of
analgesia or euphoria, or the observation that repeated
administration of the same dose results in decreased analgesia,
euphoria, or other opioid effects. It has been found that a
remarkable degree of tolerance develops to the respiratory
depressant, analgesic, sedative, emetic and euphorigenic effects of
opioids. However, the rate at which this tolerance may develop in
either an addict or in a patient requiring treatment of pain,
depends on the pattern of use. If the opioid is used frequently, it
may be necessary to increase the dose. Tolerance does not develop
equally or at the same rate to all the effects of opioids, and even
users who are highly tolerant to respiratory depressant effects
continue to exhibit miosis and constipation. Tolerance to opioids
largely disappears when the withdrawal syndrome has been
completed.
[0009] Physical dependence may develop upon repeated
administrations or extended use of opioids. Physical dependence is
gradually manifested after stopping opioid use or is precipitously
manifested (e.g., within 20 minutes) after administration of a
narcotic antagonist (referred to "precipitated withdrawal").
Depending upon the drug to which dependence has been established
and the duration of use and dose, symptoms of withdrawal vary in
number and kind, duration and severity. The most common symptoms of
the withdrawal syndrome include anorexia, weight loss, pupillary
dilation, chills alternating with excessive sweating, abdominal
cramps, nausea, vomiting, muscle spasms, hyperirritability,
lachrymation, rinorrhea, goose flesh and increased heart rate.
Abstinence syndrome typically begins to occur 24-48 hours after the
last dose, and the syndrome reaches its maximum intensity about the
third day and may not begin to decrease until the third week.
[0010] Psychological dependence (i.e., addiction) on opioids is
characterized by drug-seeking behavior directed toward achieving
euphoria and escape from, e.g., psychosocioeconomic pressures. An
addict will continue to administer opioids for non-medicinal
purposes and in the face of self-harm.
[0011] Pharmacologically, opioid antagonists typically block or
reverse all of the effect of opioid agonists. One use of opioid
antagonists is as a once-a-day treatment of naltrexone to block
euphoric effects that might be otherwise obtained upon
administration of opioids to addicts. Small doses of opioid
antagonists have been used to determine whether individuals are
physically dependent on opioids. Most commonly, opioid antagonists
are used to reverse the effects of opoids on individuals who have
overdosed on opioid agonist drugs.
[0012] There have previously been attempts in the art to control
the abuse potential associated with opioid analgesics. Typically, a
particular dose of an opioid analgesic is more potent when
administered parenterally as compared to the same dose administered
orally. Therefore, one popular mode of abuse of oral medications
involves the extraction of the opioid from the dosage form, and the
subsequent injection of the opioid (using any "suitable" vehicle
for injection) in order to achieve a "high." Attempts to curtail
abuse have therefore typically centered around the inclusion in the
oral dosage form of an opioid antagonist which is not orally active
but which will substantially block the analgesic effects of the
opioid if one attempts to dissolve the opioid and administer it
parenterally.
[0013] For example, the combination of pentazocine and naloxone has
been utilized in tablets available in the United States,
commercially available as Talwin.RTM.Nx from Sanofi-Winthrop.
Talwin.RTM.Nx contains pentazocine hydrochloride equivalent to 50
mg base and naloxone hydrochloride equivalent to 0.5 mg base.
Talwin.RTM.Nx is indicated for the relief of moderate to severe
pain. The amount of naloxone present in this combination has no
action when taken orally, and will not interfere with the
pharmacologic action of pentazocine. However, this amount of
naloxone given by injection has profound antagonistic action to
narcotic analgesics. Thus, the inclusion of naloxone is intended to
curb a form of misuse of oral pentazocine which occurs when the
dosage form is solubilized and injected. Therefore, this dosage has
lower potential for parenteral misuse than previous oral
pentazocine formulations. However, it is still subject to patient
misuse and abuse by the oral route, for example, by the patient
taking multiple doses at once.
[0014] Sunshine, et al. "Analgesic Efficacy of Pentazocine Versus a
Pentazocine-Naloxone Combination Following Oral Administration",
Clin. J. Pain, 1988:4:35-40, reported on the effect of the addition
of 0.5 mg naloxone on the analgesic efficacy of pentazocine 50 mg.
The combination was found to be significantly less efficacious than
pentazocine for the sum of the pain intensity difference (SPID),
and for relief and pain intensity difference (PID) at the fourth
hour. For patients with moderate baseline pain, the combination
produced significantly less pain relief than pentazocine for SPIED
and for relief and PID at hours 3 and 4. In patients with severe
baseline pain, there was no significant difference found between
pentazocine and the combination of pentazocine plus naloxone.
[0015] Wang, et al. "Crossover and Parallel Study of Oral
Analgesics", J. Clin Pharmacol 1981; 21:162-8, studied the
combination of naloxone 0.25 mg and Percodan.RTM. (composed of 4.5
mg oxycodone HCl, oxycodone terephthalate 0.28 mg, aspirin 224 mg,
phenacetin 160 mg, and caffeine 32 mg) compared to Percodan.RTM.
alone, and placebo in a crossover study of patients with chronic
pain. The combination had lower mean scores than Percodan.RTM.
alone for most of the analgesic hourly parameters in the later
hours of the trial. However, for the summary variables, the
combination showed no significant difference from either placebo or
Percodan.RTM..
[0016] A fixed combination of buprenorphine and naloxone was
introduced in 1991 in New Zealand (Temgesic.RTM.Nx, Reckitt &
Colman) for the treatment of pain.
[0017] A fixed combination therapy comprising tilidine (50 mg) and
naloxone (4 mg) has been available in Germany for the management of
severe pain since 1978 (Valoron.RTM.N, Goedecke). The rationale for
the combination of these drugs is effective pain relief and the
prevention of tilidine addiction through naloxone-induced
antagonisms at the morphine receptor.
[0018] U.S. Pat. No. 3,773,955 (Pachter, et al.) described orally
effective analgetic compositions which upon parenteral
administration do not produce analgesia, euphoria, or physical
dependence, and thereby prevent parenteral abuse of the analgetic
agents. Such compositions contained from about 0.1 mg to about 10
mg naloxone per analgetic oral dose. This reference was not
concerned with oral abuse of opioids.
[0019] U.S. Pat. No. 3,493,657 (Lewenstein, et al.) described
compositions comprising naloxone and morphine or oxymorphone, which
compositions were said to provide a strong analgesic effect without
the occurrence of undesired side effects such as
hallucinations.
[0020] U.S. Pat. No. 4,457,933 (Gordon, et al.) described a method
for decreasing both the oral and parenteral abuse potential of
strong analgetic agents such as oxycodone, propoxyphene and
pentazocine, by combining an analgesic dose of the opioid with
naloxone in a specific, relatively narrow range. Oxycodone-naloxone
compositions having a ratio of 2.5-5:1 parts by weight and
pentazocine-naloxone compositions having a ratio of 16-50:1 parts
by weight were preferred. The dose of naloxone which was to be
combined with the opioid is stated to substantially eliminate the
possibility of either oral or parenteral abuse of the opioid
without substantially affecting the oral analgesic activity
thereof.
[0021] U.S. Pat. No. 4,582,835 (Lewis) describes a method of
treating pain by administering a sublingually effective dose of
buprenorphine with naloxone. Lewis describes dosage ratios of
naloxone to buprenorphine from 1:3 to 1:1 for parenteral
administration, and from 1:2 to 2:1 for sublingual
administration.
[0022] It has been increasing recognized in the art that oral
opioid formulations are not only being abused by the parenteral
route, but also via the oral route when the patient or addict
orally self-administers more than the prescribed oral dose during
any dosage interval.
OBJECTS AND SUMMARY OF THE INVENTION
[0023] It is an object of the invention to provide an oral dosage
form of an opioid analgesic which is subject to less abuse
potential via the parenteral route of administration than prior
commercially available dosage forms.
[0024] It is a further object of the invention to provide a method
of treating pain in human patients with an oral dosage form of an
opioid analgesic while reducing the parenteral abuse potential of
dosage form.
[0025] It is a further object of the invention to provide a method
of manufacturing an oral dosage form of an opioid analgesic such
that it has less parenteral and/or oral abuse potential.
[0026] These objects and others are achieved by the present
invention, which is directed in part to a method of reducing the
abuse potential of an oral dosage form of an opioid analgesic,
comprising combining an analgesically effective amount of an opioid
agonist together with an opioid antagonist into an oral dosage form
which would require at least a two-step extraction process to be
separated from the opioid agonist, the amount of opioid antagonist
including being sufficient to counteract opioid effects if
extracted together with the opioid agonist and administered
parenterally. Preferably, the combination of the opioid agonist and
the opioid antagonist are only extractable from the dosage form
together, and thereafter must be separated from each other in a
separate extraction step. For example, both the opioid agonist and
the opioid antagonist may be soluble in acid, and must be separated
utilizing a high pH solution. In one preferred embodiment, the
opioid agonist is hydrocodone bitartrate and the opioid antagonist
is naltrexone hydrochloride, wherein both the hydrocodone and
naltrexone dissolve at a pH less than 8 and about 80% of said
hydrocodone and about 10% of said naltrexone are extractable at a
high pH, e.g., substantially greater than pH 10, and preferably
above pH 11.
[0027] In other embodiments, the opioid agonist is hydromorphone
hydrochloride and the opioid antagonist is naltrexone
hydrochloride, or opioid agonist is oxycodone hydrochloride and the
opioid antagonist is naltrexone hydrochloride; or the opioid
agonist is morphine sulfate and the opioid antagonist is naltrexone
hydrochloride.
[0028] In further embodiments, the method further comprises
incorporating into the dosage form a further ingredient which makes
separation of the opioid agonist from the opioid antagonist more
difficult. Such further ingredients include gelling agents, waxes,
or other pharmaceutically acceptable excipients.
[0029] In further embodiments, the method further comprises
incorporating into the preparation of the dosage form one or more
processing steps which further impede the separation of the opioid
agonist from the opioid antagonist.
[0030] In certain preferred embodiments of the method, the opioid
is hydrocodone, hydromorphone, oxycodone, morphine, or
pharmaceutically acceptable salts thereof.
[0031] In certain preferred embodiments of the method, the opioid
agonist and the opioid antagonist are combined in a ratio of opioid
antagonist to opioid agonist (analgesic) which is analgesically
effective when the combination is administered orally, but which is
aversive in a physically dependent subject. In this manner, the
combination product (antagonist/agonist) could in essence be
therapeutic to one population (patients in pain), while being
unacceptable (aversive) in a different population (e.g., physically
dependent subjects) when orally administered at the same dose or at
a higher dose than the usually prescribed dosage, e.g., about 2-3
times the usually prescribed dose of the opioid. Thus, the oral
dosage form would have less potential for parenteral as well as
oral abuse. In such embodiments where the opioid is hydrocodone and
the antagonist is naltrexone, the ratio of naltrexone to
hydrocodone is preferably from about 0.03-0.27:1 by weight, and
more preferably from about 0.05-0.20:1 by weight. In such
embodiments where the opioid antagonist is naltrexone and the
opioid agonist is hydromorphone, the ratio of naltrexone to
hydromorphone preferably is from about 0.148:1 to about 1.185:1,
and more preferably from about 0.222:1 to about 0.889:1. In such
embodiments where the opioid antagonist is naltrexone and the
opioid agonist is morphine, the ratio of naltrexone to morphine is
preferably from about 0.018:1 to about 0.148:1, and more preferably
from about 0.028:1 to about 0.111:1. In such embodiments where the
opioid antagonist is naltrexone and the opioid agonist is
oxycodone, the ratio of naltrexone to oxycodone is preferably from
about 0.037:1 to about 0.296:1, and more preferably from about
0.056:1 to about 0.222:1.
[0032] The dosage forms of the present invention may be liquids,
tablets, or multiparticulate formulations, utilizing any desired
pharmaceutically acceptable excipients known to those skilled in
the art. However, it is preferred that the opioid agonist and
opioid antagonist are incorporated into the oral dosage form in a
manner which deters the easy separation of the two drugs.
[0033] In certain embodiments, the oral dosage forms of the present
invention are sustained release formulations. This may be
accomplished, e.g., via the incorporation of a sustained release
carrier into a matrix containing the opioid agonist and opioid
antagonist; or via a sustained release coating of a matrix
containing the opioid agonist and opioid antagonist, where the
sustained release coating contains at least a portion of the
sustained release carrier included in the dosage form. In any
event, it is preferred that the sustained release preparation be
prepared in such a manner that the opioid agonist and the opioid
antagonist are combined in a matrix or interdispersed so as to
force an addict to utilize extraction methodology to separate these
drugs.
[0034] The present invention is also directed to a method of
treating pain in human patients in a manner which minimizes the
likelihood of oral abuse of opioid analgesics, comprising
administering to a human patient an oral dosage form the inventive
combinations of opioid agonist/opioid antagonist which must be
extracted in at least two separate extraction steps.
[0035] In certain embodiments, the opioid antagonist is included in
an amount (i) which does not cause a reduction in the level of
analgesia elicited from the dosage form upon oral administration to
a non-therapeutic level and (ii) which provides at least a mildly
negative, "aversive" experience in physically dependent subjects
(e.g., precipitated abstinence syndrome) when the subjects attempt
to take at least twice the usually prescribed dose at a time (and
often 2-3 times that dose or more), as compared to a comparable
dose of the opioid without the opioid antagonist present. In
certain preferred embodiments, the amount of naltrexone included in
the oral dosage form is less positively reinforcing (e.g., less
"liked") to a non-physically dependent opioid addict than a
comparable oral dosage form without the antagonist included.
Preferably, the formulation provides effective analgesia when
orally administered.
[0036] In certain preferred embodiments, the method further
comprises incorporating the opioid agonist and opioid antagonist
into a dosage form that includes a sustained release carrier,
either included in the matrix or as a sustained release coating,
such that the oral dosage form can be administered on a twice-a-day
or a once-a-day basis.
[0037] The oral pharmaceutical compositions used in the methods of
the present invention may be in the form of tablets, troches,
lozenges, aqueous or oily suspensions, dispersable powders or
granules, emulsions, hard or soft capsules or syrups or elixirs,
microparticles (e.g., microcapsules, microspheres and the like),
buccal tablets, etc.
[0038] The term "parenterally" as used herein includes subcutaneous
injections, intravenous, intramuscular, intrasternal injection or
infusion techniques.
[0039] The term "effective analgesia" is defined for purposes of
the present invention as a satisfactory reduction in or elimination
of pain, along with a tolerable level of side effects, as
determined by the human patient. It is recognized that the ratio of
opioid antagonist to opioid agonist included in certain embodiments
of the invention (e.g., where the opioid antagonist is included in
an amount (i) which does not cause a reduction in the level of
analgesia elicited from the dosage form upon oral administration to
a non-therapeutic level and (ii) which provides at least a mildly
negative, "aversive" experience in physically dependent subjects
when a large amount of the opioid, e.g., about 2-3 times the
usually prescribed dose, is taken by or administered orally to a
physically dependent subject) may decrease analgesia somewhat when
the dosage form is orally administered as assessed by direct
measurement in patients or by the use of one or more surrogate
measures of opioid analgesic efficacy in human subjects such as a
Visual Analogue Scale ("VAS") for "drug effect". The patient in
pain may or may not appreciably notice the difference between the
formulation administered in accordance with such embodiments of the
invention, and a similar formulation which includes the same dose
of opioid agonist without the opioid antagonist, but will obtain an
analgesic effect from the combination. Surrogate measures of opioid
efficacy (analgesia) include sedation, respiratory rate and/or
pupil size (via pupillometry), and visual analogue scale ("VAS")
for "drug effect". In such embodiments, such surrogate measures are
affected in a direction which indicates reduced opioid effect, as
compared to the same dose of opioid without the concommitant dose
of opioid antagonist. The pharmacodynamic effect (analgesia) of the
formulations administered in accordance with the invention can be
described by means of, for example, scores from an analgesic
questionnaire reported by the patients at serial times following
administration of the dosage form. Summary measures of analgesia
include the sum of pain intensity difference (SPID) and total pain
relief (TOTPAR).
[0040] The term "sustained release" is defined for purposes of the
present invention as the release of the drug (opioid analgesic)
from the transdermal formulation at such a rate that blood (e.g.,
plasma) concentrations (levels) are maintained within the
therapeutic range (above the minimum effective analgesic
concentration or "MEAC") but below toxic levels over a period of
time indicative of a twice-a-day or a once-a-day formulation.
[0041] For purposes of the present invention, the term "opioid
agonist" is interchangeable with the term "opioid" or "opioid
analgesic" and shall include the base of the opioid,
pharmaceutically acceptable salts thereof, stereoisomers thereof,
ethers and esters thereof, mixed agonist-antagonists, and partial
agonists.
[0042] For purposes of the present invention, the term "opioid
antagonist" shall include the base, pharmaceutically acceptable
salts thereof, stereoisomers thereof, ethers and esters thereof,
and mixtures thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0043] It has been postulated that there exists at least three
subspecies of opioid receptors, designated mu, kappa, and delta.
Within this framework, the mu receptor is considered to be involved
in the production of superspinal analgesia, respiratory depression,
euphoria, and physical dependence. The kappa receptor is considered
to be involved in inducing spinal analgesia, miosis and sedation.
Activation of the gamma receptors causes dysphoria and
hallucinations, as well as respiratory and vasomotor stimulatory
effects. A receptor distinct from the mu receptor and designated
gamma has been described in the mouse vas deferens, Lord, et al.
Nature, 1977, 267, 495-99. Opioid agonists are thought to exert
their agonist actions primarily at the mu receptor and to a lesser
degree at the kappa receptor. There are a few drugs that appear to
act as partial agonists at one receptor type or another. Such drugs
exhibit a ceiling effect. Such drugs include nalorphine, propiram,
and buprenorphine. Still other drugs act as competitive antagonists
at the mu receptor and block the effects of morphine-like drugs, by
exerting agonist actions at the kappa and omega receptors. The term
"agonist-antagonist" has evolved to describe such mechanism of
actions. The concept of antagonism to the actions of opioids is
considered to be complex.
[0044] It has been found with the administration of opioid
agonist-antagonists and partial agonists that tolerance develops to
the agonist effects but not to the antagonist effects of the drugs.
Even after prolonged administration of high doses, discontinuance
of naloxone is not characterized by any recognizable withdrawal
syndrome, and withdrawal of naltrexone, another relatively pure
opioid antagonist, produces very few signs and symptoms. However,
after prolonged administration of high dosage, abrupt
discontinuation of opioid agonist-antagonists nalorphine or
cyclazocine causes a characteristic withdrawal syndrome that is
similar for both drugs.
[0045] Naloxone is an opioid antagonist which is almost void of
agonist effects. Subcutaneous doses of up to 12 mg of naloxone
produce no discernable subjective effects, and 24 mg naloxone
causes only slight drowsiness. Small doses (0.4-0.8 mg) of naloxone
given intramuscularly or intravenously in man prevent or promptly
reverse the effects of morphine-like opioid agonist. One mg of
naloxone intravenously has been reported to completely block the
effect of 25 mg of heroin. The effects of naloxone are seen almost
immediately after intravenous administration. The drug is absorbed
after oral administration, but has been reported to be metabolized
into an inactive form rapidly in its first passage through the
liver such that it has been reported to be only one fiftieth as
potent as when parenterally administered. Oral dosage of more than
1 g have been reported to be almost completely metabolized in less
than 24 hours.
[0046] Other opioid antagonists, for example, cyclazocine and
naltrexone, both of which have cyclopropylmethyl substitutions on
the nitrogen, retain much of their efficacy by the oral route and
their durations of action are much longer, approaching 24 hours
after oral doses. A most preferred opioid antagonist is naltrexone.
However, equiantagonistic oral doses of other opioid antagonists,
including but not limited to naloxone, nalmephene, cyclazocine, and
levallorphan can be utilized in accordance with the present
invention. The ratio of such other antagonists to a particular
opioid agonist can be readily determined without undue
experimentation by one skilled in art who desires to utilize a
different opioid antagonist than naltrexone, the ratio of which to
opioid agonists is exemplified and discussed in detail herein.
Those skilled in the art may determine such ratios of other
antagonists to opioid agonists, e.g., by conducting the same or
similar clinical studies set forth in the examples appended herein.
Thus, combinations of opioid antagonists/opioid agonists which are
orally administered in ratios which are equivalent to the ratio of,
e.g., naltrexone to hydrocodone set forth herein are considered to
be within the scope of the present invention and within the scope
of the appended claims. For example, in certain embodiments of the
invention, naloxone is utilized as the opioid antagonist, the
amount of naloxone included in the dosage form being large enough
to provide an equiantagonistic effect as if naltrexone were
included in the combination.
[0047] In the treatment of patients previously addicted to opioids,
naltrexone has been used in large oral doses (over 100 mg) to
prevent euphorigenic effects of opioid agonists. Naltrexone has
been reported to exert strong preferential blocking action against
mu over delta sites. Naltrexone is known as a synthetic congener of
oxymorphone with no opioid agonist properties, and differs in
structure from oxymorphone by the replacement of the methyl group
located on the nitrogen atom of oxymorphone with a
cyclopropylmethyl group. The hydrochloride salt of naltrexone is
soluble in water up to about 100 mg/cc. The pharmacological and
pharmacokinetic properties of naltrexone have been evaluated in
multiple animal and clinical studies. See, e.g., Gonzalez J P, et
al. Naltrexone: A review of its Pharmacodynamic and Pharmacokinetic
Properties and Therapeutic Efficacy in the Management of Opioid
Dependence. Drugs 1988; 35:192-213, hereby incorporated by
reference. Following oral administration, naltrexone is rapidly
absorbed (within 1 hour) and has an oral bioavailability ranging
from 5-40%. Naltrexone's protein binding is approximately 21% and
the volume of distribution following single-dose administration is
16.1 L/kg.
[0048] Naltrexone is commercially available in tablet form
(Revia.RTM., DuPont) for the treatment of alcohol dependence and
for the blockade of exogenously administered opioids. See, e.g.,
Revia (naltrexone hydrochloride tablets). Physician's Desk
Reference 51.sup.st ed., Montvale, N.J. Medical Economics 1997;
51:957-959. A dosage of 50 mg ReVia.RTM. blocks the pharmacological
effects of 25 mg IV administered heroin for up to 24 hours.
[0049] It is known that when coadministered with morphine, heroin
or other opioids on a chronic basis, naltrexone blocks the
development of physical dependence to opioids. It is believed that
the method by which naltrexone blocks the effects of heroin is by
competitively binding at the opioid receptors. Naltrexone has been
used to treat narcotic addiction by complete blockade of the
effects of opioids. It has been found that the most successful use
of naltrexone for a narcotic addiction is with good prognosis
narcotic addicts as part of a comprehensive occupational or
rehabilitative program involving behavioral control or other
compliance enhancing methods. For treatment of narcotic dependence
with naltrexone, it is desirable that the patient be opioid-free
for at least 7-10 days. The initial dosage of naltrexone for such
purposes has typically been about 25 mg, and if no withdrawal signs
occur, the dosage may be increased to 50 mg per day. A daily dosage
of 50 mg is considered to produce adequate clinical blockade of the
actions of parenterally administered opioids. Naltrexone has also
been used for the treatment of alcoholism as an adjunct with social
and psychotherapeutic methods.
[0050] In the dosage forms and methods of the invention, the amount
of naltrexone included is significantly less than the dosages
previously commercially available. This is in part because the use
of naltrexone is different in the present invention: the goal is
not to block opioid effects, but rather to provide a negative,
"aversive" experience when a large amount of the combination
product, e.g., about 2-3 times the usually prescribed dose, is
taken by or administered to a physically dependent subject.
[0051] Thus, for example, in formulations of the present invention
in which the opioid is hydrocodone bitartrate 15 mg, the amount of
naltrexone hydrochloride included in the formulation is from about
0.5 mg to about 4 mg, and preferably from about 0.75 mg to about 3
mg naltrexone per 15 mg hydrocodone.
[0052] Opioid analgesics which are useful in the present invention
include all opioid agonists or mixed agonist-antagonists, partial
agonists, including but not limited to alfentanil, allylprodine,
alphaprodine, anileridine, benzylmorphine, bezitramide,
buprenorphine, butorphanol, clonitazene, codeine, desomorphine,
dextromoramide, dezocine, diampromide, diamorphone, dihydrocodeine,
dihydromorphine, dimenoxadol, dimepheptanol, dimethylthiambutene,
dioxaphetyl butyrate, dipipanone, eptazocine, ethoheptazine,
ethylmethylthiambutene, ethylmorphine, etonitazene, fentanyl,
heroin, hydrocodone, hydromorphone, hydroxypethidine, isomethadone,
ketobemidone, levorphanol, levophenacylmorphan, lofentanil,
meperidine, meptazinol, metazocine, methadone, metopon, morphine,
myrophine, narceine, nicomorphine, norlevorphanol, nornethadone,
nalorphine, nalbuphene, normorphine, norpipanone, opium, oxycodone,
oxymorphone, papaveretum, pentazocine, phenadoxone, phenomorphan,
phenazocine, phenoperidine, piminodine, piritramide, propheptazine,
promedol, properidine, propoxyphene, sufentanil, tilidine,
tramadol, mixtures of any of the foregoing, salts of any of the
foregoing, and the like.
[0053] In certain preferred embodiments, the opioid agonist or
analgesic is selected from the group consisting of hydrocodone,
morphine, hydromorphone, oxycodone, codeine, levorphanol,
meperidine, methadone, or salts thereof, or mixtures thereof. In
certain preferred embodiments, the opioid agonist is hydrocodone.
Equianalgesic doses of these opioids, in comparision to a 15 mg
dose of hydrocodone, are set forth in Table 1 below:
1TABLE 1 Equianalgesic Doses of Opioids Opioid Calculated Dose (mg)
Oxycodone 13.5 Codeine 90.0 Hydrocodone 15.0 Hydromorphone 3.375
Levorphanol 1.8 Meperidine 135.0 Methadone 9.0 Morphine 27.0
[0054] Based on the preferred ratio of naltrexone in an amount from
about 0.5 to about 4 mg per 15 mg of hydrocodone, the approximate
ratio of naltrexone to 1 mg of each opioid is set forth in Table
2:
2TABLE 2 Weight Ratio of Naltrexone per Dose Opioid Weight Ratio
Naltrexone per Opioid 1 mg Opioid Oxycodone 0.037 to 0.296 Codeine
0.005 to 0.044 Hydrocodone 0.033 to 0.267 Hydromorphone 0.148 to
1.185 Levorphanol 0.278 to 2.222 Meperidine 0.0037 to 0.0296
Methadone 0.056 to 0.444 Morphine 0.018 to 0.148
[0055] Based on the more preferred ratio of about 0.75 mg to about
3 mg naltrexone per 15 mg hydrocodone of naltrexone, the
approximate ratio of naltrexone to 1 mg of each opioid is set forth
in Table 3:
3TABLE 3 Weight Ratio of Naltrexone per Dose Opioid Opioid Weight
Ratio Naltrexone Oxycodone 0.056 to 0.222 Codeine 0.0083 to 0.033
Hydrocodone 0.050 to 0.200 Hydromorphone 0.222 to 0.889 Levorphanol
0.417 to 1.667 Meperidine 0.0056 to 0.022 Methadone 0.083 to 0.333
Morphine 0.028 to 0.111
[0056] Although hydrocodone is effective in the management of pain,
there has been an increase in its abuse by individuals who are
psychologically dependent on opioids or who misuse opioids for
non-therapeutic reasons. Previous experience with other opioids has
demonstrated a decreased abuse potential when opioids are
administered in combination with a narcotic antagonist especially
in patients who are ex-addicts. Weinhold L L, et al. Buprenorphine
Alone and in Combination with Naltrexone in Non-Dependent Humans,
Drug and Alcohol Dependence 1992; 30:263-274; Mendelson J., et.
al., Buprenorphine and Naloxone Interactions in Opiate-Dependent
Volunteers, Clin Pharm Ther 1996; 60:105-114; both of which are
hereby incorporated by reference.
[0057] Hydrocodone is a semisynthetic narcotic analgesic and
antitussive with multiple central nervous system and
gastrointestinal actions. Chemically, hydrocodone is
4,5-epoxy-3-methoxy-17-methylmorphinan-6-one, and is also known as
dihydrocodeinone. Like other opioids, hydrocodone may be habit
forming and may produce drug dependence of the morphine type. In
excess doses hydrocodone, like other opium derivatives, will
depress respiration.
[0058] Oral hydrocodone is also available in Europe (Belgium,
Germany, Greece, Italy, Luxembourg, Norway and Switzerland) as an
antitussive agent. A parenteral formulation is also available in
Germany as an antitussive agent. For use as an analgesic,
hydrocodone bitartrate is commercially available in the United
States only as a fixed combination with non-opiate drugs (i.e.,
ibuprofen, acetaminophen, aspirin, etc.) for relief of moderate or
moderately severe pain.
[0059] A common dosage form of hydrocodone is in combination with
acetaminophen, and is commercially available, e.g., as Lortab.RTM.
in the U.S. from UCB Pharma, Inc. as 2.5/500 mg, 5/500 mg, 7.5/500
mg and 10/500 mg hydrocodone/acetaminophen tablets. Tablets are
also available in the ratio of 7.5 mg hydrocodone bitartrate and
650 mg acetaminophen; and 7.5 mg hydrocodone bitartrate and 750 mg
acetaminophen. Hydrocodone in combination with aspirin is given in
an oral dosage form to adults generally in 1-2 tablets every 4-6
hours as needed to alleviate pain. The tablet form is 5 mg
hydrocodone bitartrate and 224 mg aspirin with 32 mg caffeine; or 5
mg hydrocodone bitartrate and 500 mg aspirin. A relatively new
formulation comprises hydrocodone bitartrate and ibuprofen.
Vicoprofen.RTM., commercially available in the U.S. from Knoll
Laboratories, is a tablet containing 7.5 mg hydrocodone bitartrate
and 200 mg ibuprofen. The present invention is contemplated to
encompass all such formulations, with the inclusion of the orally
active opioid antagonist within the inventive amounts set forth
herein.
[0060] The abuse potential of opioid analgesics such as hydrocodone
is surprisingly curtailed by the inventive combinations of the
present invention. More particularly, it has been discovered that
it is possible to combine in a single oral dosage form an opioid
analgesic together with a small amount of opioid antagonist, to
achieve a product which still provides analgesia but which
substantially negates the possibility that a physically dependent
human subject will continue to abuse the drug by taking more than
one tablet at a time, e.g., 2-3 times more than the usually
prescribed dose.
[0061] The oral dosage forms of the invention comprise an orally
therapeutically effective amount of an opioid agonist, together
with an opioid antagonist such as naltrexone in an amount (i) which
does not cause a reduction in the level of analgesia elicited from
the dosage form upon oral administration to a non-therapeutic level
and (ii) which provides at least a mildly negative, "aversive"
experience in physically dependent human subjects, for example,
physically dependent addicts (e.g., precipitated abstinence
syndrome) when taking more than the usually prescribed dose at a
time. Preferably, the amount of antagonist included in the oral
dosage form is (iii) less positively reinforcing (e.g., less
"liked") by a non-physically dependent human subject, e.g., opioid
addict, than a comparable oral dosage form without the antagonist
included.
[0062] The amount of antagonist which is useful to achieve
parameters (i)-(iii) set forth in the preceding paragraph may be
determined at least in part, for example, through the use of
"surrogate" tests, such as a VAS scale (where the subject grades
his/her perception of the effect of the dosage form) and/or via a
measurement such as pupil size (measured by pupillometry). Such
measurements allow one skilled in the art to determine the dose of
antagonist relative to the dose of agonist which causes a
diminution in the opiate effects of the agonist. Subsequently, one
skilled in the art can determine the level of opioid antagonist
that causes aversive effects in physically dependent subjects as
well as the level of opioid antagonist that minimizes "liking
scores" or opioid reinforcing properties in non-physically
dependent addicts. Once these levels of opioid antagonist are
determined, it is then possible to determine the range of
antagonist dosages at or below this level which would be useful in
achieving parameters (i)-(iii) set forth in the preceding
paragraph.
[0063] The combination of opioid agonist and opioid antagonist can
be employed in admixtures with conventional excipients, i.e.,
pharmaceutically acceptable organic or inorganic carrier substances
suitable for oral administration, known to the art. Suitable
pharmaceutically acceptable carriers include but are not limited to
water, salt solutions, alcohols, gum arabic, vegetable oils, benzyl
alcohols, polyethylene glycols, gelate, carbohydrates such as
lactose, amylose or starch, magnesium stearate talc, silicic acid,
viscous paraffin, perfume oil, fatty acid monoglycerides and
diglycerides, pentaerythritol fatty acid esters,
hydroxymethylcellulose, polyvinylpyrrolidone, etc. The
pharmaceutical preparations can be sterilized and if desired mixed
with auxiliary agents, e.g., lubricants, preservatives,
stabilizers, wetting agents, emulsifiers, salts for influencing
osmotic pressure buffers, coloring, flavoring and/or aromatic
substances and the like. They can also be combined where desired
with other active agents, e.g., other analgesic agents. For oral
administration, particularly suitable are tablets, dragees,
liquids, drops, suppositories, or capsules, caplets and gelcaps.
The compositons intended for oral use may be prepared according to
any method known in the art and such compositions may contain one
or more agents selected from the group consisting of inert,
non-toxic pharmaceutically excipients which are suitable for the
manufacture of tablets. Such excipients include, for example an
inert diluent such as lactose; granulating and disintegrating
agents such as cornstarch; binding agents such as starch; and
lubricating agents such as magnesium stearate. The tablets may be
uncoated or they may be coated by known techniques for elegance or
to delay release of the active ingredients. Formulations for oral
use may also be presented as hard gelatin capsules wherein the
active ingredient is mixed with an inert diluent.
[0064] Aqueous suspensions contain the above-identified combination
of drugs and that mixture has one or more excipients suitable as
suspending agents, for example pharmaceutically acceptable
synthetic gums such as hydroxypropylmethylcellulose or natural
gums. Oily suspensions may be formulated by suspending the
above-identified combination of drugs in a vegetable oil or mineral
oil. The oily suspensions may contain a thickening agent such as
beeswax or cetyl alcohol. A syrup, elixir, or the like can be used
wherein a sweetened vehicle is employed. Injectable suspensions may
also be prepared, in which case appropriate liquid carriers,
suspending agents and the like may be employed.
[0065] The method of treatment and pharmaceutical formulations of
the present invention may further include one or more drugs in
addition to the opioid analgesic and opioid antagonist, which
additional drug(s) may or may not act synergistically therewith.
Thus, in certain embodiments, a combination of two opioid
analgesics may be included in the formulation, in addition to the
opioid antagonist. For example, the dosage form may include two
opioid analgesics having different properties, such as half-life,
solubility, potency, and a combination of any of the foregoing. In
yet further embodiments, one or more opioid analgesics is included
and a further non-opioid drug is also included, in addition to the
opioid antagonist. Such non-opioid drugs would preferably provide
additional analgesia, and include, for example, aspirin;
acetaminophen; non-sterioidal antiinflammatory drugs ("NSAIDS"),
e.g., ibuprofen, ketoprofen, etc.; N-methyl-D-aspartate (NMDA)
receptor antagonists, e.g., a morphinan such as dextromethorphan or
dextrorphan, or ketamine; cycooxygenase-II inhibitors ("COX-1
inhibitors"); and/or glycine receptor antagonists.
[0066] In certain preferred embodiments of the present invention,
the invention allows for the use of lower doses of the opioid
analgesic by virtue of the inclusion of an additional non-opioid
agonist, such as an NSAID or a COX-2 inhibitor. By using lower
amounts of either or both drugs, the side effects associated with
effective pain management in humans are reduced.
[0067] Suitable non-steroidal anti-inflammatory agents, including
ibuprofen, diclofenac, naproxen, benoxaprofen, flurbiprofen,
fenoprofen, flubufen, ketoprofen, indoprofen, piroprofen,
carprofen, oxaprozin, pramoprofen, muroprofen, trioxaprofen,
suprofen, aminoprofen, tiaprofenic acid, fluprofen, bucloxic acid,
indomethacin, sulindac, tolmetin, zomepirac, tiopinac, zidometacin,
acemetacin, fentiazac, clidanac, oxpinac, mefenamic acid,
meclofenamic acid, flufenamic acid, niflumic acid, tolfenamic acid,
diflurisal, flufenisal, piroxicam, sudoxicam or isoxicam, and the
like. Useful dosages of these drugs are well known to those skilled
in the art.
[0068] N-methyl-D-aspartate (NMDA) receptor antagonists are well
known in the art, and encompass, for example, morphinans such as
dextromethorphan or dextrorphan, ketamine, d-methadone or
pharmaceutically acceptable salts thereof. For purposes of the
present invention, the term "NMDA antagonist" is also deemed to
encompass drugs that block a major intracellular consequence of
NMDA-receptor activation, e.g. a ganglioside such as GM.sub.1 or
GT.sub.1b a phenothiazine such as trifluoperazine or a
naphthalenesulfonamide such as
N-(6-aminothexyl)-5-chloro-1-naphthalene- sulfonamide. These drugs
are stated to inhibit the development of tolerance to and/or
dependence on addictive drugs, e.g., narcotic analgesics such as
morphine, codeine, etc. in U.S. Pat. Nos. 5,321,012 and 5,556,838
(both to Mayer, et. al.), and to treat chronic pain in U.S. Pat.
No. 5,502,058 (Mayer, et. al.), all of which are hereby
incorporated by reference. The NMDA antagonist may be included
alone, or in combination with a local anesthetic such as lidocaine,
as described in these Mayer, et. al. patents.
[0069] The treatment of chronic pain via the use of glycine
receptor antagonists and the identification of such drugs is
described in U.S. Pat. No. 5,514,680 (Weber, et al.), hereby
incorporated by reference.
[0070] COX-2 inhibitors have been reported in the art and many
chemical structures are known to produce inhibition of
cyclooxygenase-2. COX-2 inhibitors are described, for example, in
U.S. Pat. Nos. 5,616,601; 5,604,260; 5,593,994; 5,550,142;
5,536,752; 5,521,213; 5,475,995; 5,639,780; 5,604,253; 5,552,422;
5,510,368; 5,436,265; 5,409,944; and 5,130,311, all of which are
hereby incorporated by reference. Certain preferred COX-2
inhibitors include celecoxib (SC-58635), DUP-697, flosulide
(CGP-28238), meloxicam, 6-methoxy-2 naphthylacetic acid (6-MNA),
MK-966, nabumetone (prodrug for 6-MNA), nimesulide, NS-398,
SC-5766, SC-58215, T-614; or combinations thereof. Dosage levels of
COX-2 inhibitor on the order of from about 0.005 mg to about 140 mg
per kilogram of body weight per day are therapeutically effective
in combination with an opioid analgesic. Alternatively, about 0.25
mg to about 7 g per patient per day of a COX-2 inhibitor is
administered in combination with an opioid analgesic.
[0071] In yet further embodiments, a non-opioid drug can be
included which provides a desired effect other than analgesia,
e.g., antitussive, expectorant, decongestant, antihistamine drugs,
local anesthetics, and the like.
[0072] An oral dosage form according to the invention may be
provided as, for example, granules, spheroids, beads, pellets
(hereinafter collectively referred to as "multiparticulates"). An
amount of the multiparticulates which is effective to provide the
desired dose of opioid over time may be placed in a capsule or may
be incorporated in any other suitable oral solid form.
Alternatively, the oral dosage form may be in the form of a
tablet.
Controlled Release Dosage Forms
[0073] The opioid agonist/opioid antagonist combination can be
formulated as a controlled or sustained release oral formulation in
any suitable tablet, coated tablet or multiparticulate formulation
known to those skilled in the art. The sustained release dosage
form may optionally include a sustained release carrier which is
incorporated into a matrix along with the opioid agonist and opioid
antagonist, or may be applied as a sustained release coating.
[0074] In embodiments in which the opioid analgesic comprises
hydrocodone, the sustained release oral dosage forms may include
analgesic doses from about 8 mg to about 50 mg of hydrocodone per
dosage unit. In sustained release oral dosage forms where
hydromorphone is the therapeutically active opioid, it is included
in an amount from about 2 mg to about 64 mg hydromorphone
hydrochloride. In another embodiment, the opioid analgesic
comprises morphine, and the sustained release oral dosage forms of
the present invention include from about 2.5 mg to about 800 mg
morphine, by weight. In yet another embodiment, the opioid
analgesic comprises oxycodone and the sustained release oral dosage
forms include from about 2.5 mg to about 800 mg oxycodone. The
opioid analgesic may comprise tramadol and the sustained release
oral dosage forms may include from about 25 mg to 800 mg tramadol
per dosage unit. The dosage form may contain more than one opioid
analgesic to provide a substantially equivalent therapeutic effect.
Alternatively, the dosage form may contain molar equivalent amounts
of other salts of the opioids useful in the present invention.
[0075] In one preferred embodiment of the present invention, the
sustained release dosage form comprises such particles containing
or comprising the active ingredient, wherein the particles have
diameter from about 0.1 mm to about 2.5 mm, preferably from about
0.5 mm to about 2 mm.
[0076] The particles are preferably film coated with a material
that permits release of the opioid agonist/antagonist combination
at a sustained rate in an aqueous medium. The film coat is chosen
so as to achieve, in combination with the other stated properties,
a desired in-vitro release rate. The sustained release coating
formulations of the present invention should be capable of
producing a strong, continuous film that is smooth and elegant,
capable of supporting pigments and other coating additives,
non-toxic, inert, and tack-free.
[0077] In certain embodiments, the particles comprise normal
release matrixes containing the opioid analgesic with the opioid
antagonist.
Coatings
[0078] The dosage forms of the present invention may optionally be
coated with one or more materials suitable for the regulation of
release or for the protection of the formulation. In one
embodiment, coatings are provided to permit either pH-dependent or
pH-independent release, e.g., when exposed to gastrointestinal
fluid. A pH-dependent coating serves to release the opioid in
desired areas of the gastro-intestinal (GI) tract, e.g., the
stomach or small intestine, such that an absorption profile is
provided which is capable of providing at least about eight hours
and preferably about twelve hours to up to about twenty-four hours
of analgesia to a patient. When a pH-independent coating is
desired, the coating is designed to achieve optimal release
regardless of pH-changes in the environmental fluid, e.g., the GI
tract. It is also possible to formulate compositions which release
a portion of the dose in one desired area of the GI tract, e.g.,
the stomach, and release the remainder of the dose in another area
of the GI tract, e.g., the small intestine.
[0079] Formulations according to the invention that utilize
pH-dependent coatings to obtain formulations may also impart a
repeat-action effect whereby unprotected drug is coated over the
enteric coat and is released in the stomach, while the remainder,
being protected by the enteric coating, is released further down
the gastrointestinal tract. Coatings which are pH-dependent may be
used in accordance with the present invention include shellac,
cellulose acetate phthalate (CAP), polyvinyl acetate phthalate
(PVAP), hydroxypropylmethylcellulose phthalate, and methacrylic
acid ester copolymers, zein, and the like.
[0080] In certain preferred embodiments, the substrate (e.g.,
tablet core bead, matrix particle) containing the opioid analgesic
(with or without the COX-2 inhibitor) is coated with a hydrophobic
material selected from (i) an alkylcellulose; (ii) an acrylic
polymer; or (iii) mixtures thereof. The coating may be applied in
the form of an organic or aqueous solution or dispersion. The
coating may be applied to obtain a weight gain from about 2 to
about 25% of the substrate in order to obtain a desired sustained
release profile. Coatings derived from aqueous dispersions--are
described, e.g., in detail in U.S. Pat. Nos. 5,273,760 and
5,286,493, assigned to the Assignee of the present invention and
hereby incorporated by reference.
[0081] Other examples of sustained release formulations and
coatings which may be used in accordance with the present invention
include Assignee's U.S. Pat. Nos. 5,324,351; 5,356,467, and
5,472,712, hereby incorporated by reference in their entirety.
[0082] Alkylcellulose Polymers
[0083] Cellulosic materials and polymers, including
alkylcelluloses, provide hydrophobic materials well suited for
coating the beads according to the invention. Simply by way of
example, one preferred alkylcellulosic polymer is ethylcellulose,
although the artisan will appreciate that other cellulose and/or
alkylcellulose polymers may be readily employed, singly or in any
combination, as all or part of a hydrophobic coating according to
the invention.
[0084] One commercially-available aqueous dispersion of
ethylcellulose is Aquacoat.RTM. (FMC Corp., Philadelphia, Pa.,
U.S.A.). Aquacoat.RTM. is prepared by dissolving the ethylcellulose
in a water-immiscible organic solvent and then emulsifying the same
in water in the presence of a surfactant and a stabilizer. After
homogenization to generate submicron droplets, the organic solvent
is evaporated under vacuum to form a pseudolatex. The plasticizer
is not incorporated in the pseudolatex during the manufacturing
phase. Thus, prior to using the same as a coating, it is necessary
to intimately mix the Aquacoat.RTM. with a suitable plasticizer
prior to use.
[0085] Another aqueous dispersion of ethylcellulose is commercially
available as Surelease.RTM. (Colorcon, Inc., West Point, Pa.,
U.S.A.). This product is prepared by incorporating plasticizer into
the dispersion during the manufacturing process. A hot melt of a
polymer, plasticizer (dibutyl sebacate), and stabilizer (oleic
acid) is prepared as a homogeneous mixture, which is then diluted
with an alkaline solution to obtain an aqueous dispersion which can
be applied directly onto substrates.
[0086] Acrylic Polymers
[0087] In other preferred embodiments of the present invention, the
hydrophobic material comprising the controlled release coating is a
pharmaceutically acceptable acrylic polymer, including but not
limited to acrylic acid and methacrylic acid copolymers, methyl
methacrylate copolymers, ethoxyethyl methacrylates, cyanoethyl
methacrylate, poly(acrylic acid), poly(methacrylic acid),
methacrylic acid alkylamide copolymer, poly(methyl methacrylate),
polymethacrylate, poly(methyl methacrylate) copolymer,
polyacrylamide, aminoalkyl methacrylate copolymer, poly(methacrylic
acid anhydride), and glycidyl methacrylate copolymers.
[0088] In certain preferred embodiments, the acrylic polymer is
comprised of one or more ammonio methacrylate copolymers. Ammonio
methacrylate copolymers are well known in the art, and are
described in NF XVII as fully polymerized copolymers of acrylic and
methacrylic acid esters with a low content of quaternary ammonium
groups.
[0089] In order to obtain a desirable dissolution profile, it may
be necessary to incorporate two or more ammonio methacrylate
copolymers having differing physical properties, such as different
molar ratios of the quaternary ammonium groups to the neutral
(meth)acrylic esters.
[0090] Certain methacrylic acid ester-type polymers are useful for
preparing pH-dependent coatings which may be used in accordance
with the present invention. For example, there are a family of
copolymers synthesized from diethylaminoethyl methacrylate and
other neutral methacrylic esters, also known as methacrylic acid
copolymer or polymeric methacrylates, commercially available as
Eudragit.RTM. from Rohm Tech, Inc. There are several different
types of Eudragit.RTM.. For example, Eudragit.RTM. E is an example
of a methacrylic acid copolymer which swells and dissolves in
acidic media. Eudragit.RTM. L is a methacrylic acid copolymer which
does not swell at about pH <5.7 and is soluble at about pH
>6. Eudragit.RTM. S does not swell at about pH <6.5 and is
soluble at about pH >7. Eudragit.RTM. RL and Eudragit.RTM. RS
are water swellable, and the amount of water absorbed by these
polymers is pH-dependent, however, dosage forms coated with
Eudragit.RTM. RL and RS are pH-independent.
[0091] In certain preferred embodiments, the acrylic coating
comprises a mixture of two acrylic resin lacquers commercially
available from Rohm Pharma under the Tradenames Eudragit.RTM. RL30D
and Eudragit.RTM. RS30D, respectively. Eudragit.RTM. RL30D and
Eudragit.RTM. RS30D are copolymers of acrylic and methacrylic
esters with a low content of quaternary ammonium groups, the molar
ratio of ammonium groups to the remaining neutral (meth)acrylic
esters being 1:20 in Eudragit.RTM. RL30D and 1:40 in Eudragit.RTM.
RS30D. The mean molecular weight is about 150,000. The code
designations RL (high permeability) and RS (low permeability) refer
to the permeability properties of these agents. Eudragit.RTM. RL/RS
mixtures are insoluble in water and in digestive fluids. However,
coatings formed from the same are swellable and permeable in
aqueous solutions and digestive fluids.
[0092] The Eudragit.RTM. RL/RS dispersions of the present invention
may be mixed together in any desired ratio in order to ultimately
obtain a sustained release formulation having a desirable
dissolution profile. Desirable sustained release formulations may
be obtained, for instance, from a retardant coating derived from
100% Eudragit.RTM. RL, 50% Eudragit.RTM. RL and 50% Eudragit.RTM.
RS, and 10% Eudragit.RTM. RL:Eudragit.RTM. 90% RS. Of course, one
skilled in the art will recognize that other acrylic polymers may
also be used, such as, for example, Eudragit.RTM. L.
[0093] Plasticizers
[0094] In embodiments of the present invention where the coating
comprises an aqueous dispersion of a hydrophobic material, the
inclusion of an effective amount of a plasticizer in the aqueous
dispersion of hydrophobic material will further improve the
physical properties of the sustained release coating. For example,
because ethylcellulose has a relatively high glass transition
temperature and does not form flexible films under normal coating
conditions, it is preferable to incorporate a plasticizer into an
ethylcellulose coating containing sustained release coating before
using the same as a coating material. Generally, the amount of
plasticizer included in a coating solution is based on the
concentration of the film-former, e.g., most often from about 1 to
about 50 percent by weight of the film-former. Concentration of the
plasticizer, however, can only be properly determined after careful
experimentation with the particular coating solution and method of
application.
[0095] Examples of suitable plasticizers for ethylcellulose include
water insoluble plasticizers such as dibutyl sebacate, diethyl
phthalate, triethyl citrate, tributyl citrate, and triacetin,
although it is possible that other water-insoluble plasticizers
(such as acetylated monoglycerides, phthalate esters, castor oil,
etc.) may be used. Triethyl citrate is an especially preferred
plasticizer for the aqueous dispersions of ethyl cellulose of the
present invention.
[0096] Examples of suitable plasticizers for the acrylic polymers
of the present invention include, but are not limited to citric
acid esters such as triethyl citrate NF XVI, tributyl citrate,
dibutyl phthalate, and possibly 1,2-propylene glycol. Other
plasticizers which have proved to be suitable for enhancing the
elasticity of the films formed from acrylic films such as
Eudragit.RTM. RL/RS lacquer solutions include polyethylene glycols,
propylene glycol, diethyl phthalate, castor oil, and triacetin.
Triethyl citrate is an especially preferred plasticizer for the
aqueous dispersions of ethyl cellulose of the present
invention.
[0097] It has further been found that the addition of a small
amount of talc reduces the tendency of the aqueous dispersion to
stick during processing, and acts as a polishing agent.
Processes for Preparing Coated Beads
[0098] When a hydrophobic material is used to coat inert
pharmaceutical beads such as nu pariel 18/20 beads, a plurality of
the resultant solid controlled release beads may thereafter be
placed in a gelatin capsule in an amount sufficient to provide an
effective controlled release dose when ingested and contacted by an
environmental fluid, e.g., gastric fluid or dissolution media.
[0099] The controlled release bead formulations of the present
invention slowly release the therapeutically active agent, e.g.,
when ingested and exposed to gastric fluids, and then to intestinal
fluids. The controlled release profile of the formulations of the
invention can be altered, for example, by varying the amount of
overcoating with the hydrophobic material, altering the manner in
which the plasticizer is added to the hydrophobic material, by
varying the amount of plasticizer relative to hydrophobic material,
by the inclusion of additional ingredients or excipients, by
altering the method of manufacture, etc. The dissolution profile of
the ultimate product may also be modified, for example, by
increasing or decreasing the thickness of the retardant
coating.
[0100] Spheroids or beads coated with a therapeutically active
agent are prepared, e.g., by dissolving the therapeutically active
agent in water and then spraying the solution onto a substrate, for
example, nu pariel 18/20 beads, using a Wuster insert. Optionally,
additional ingredients are also added prior to coating the beads in
order to assist the binding of the opioid to the beads, and/or to
color the solution, etc. For example, a product which includes
hydroxypropylmethylcellulose, etc. with or without colorant (e.g.,
Opadry.RTM., commercially available from Colorcon, Inc.) may be
added to the solution and the solution mixed (e.g., for about 1
hour) prior to application of the same onto the beads. The
resultant coated substrate, in this example beads, may then be
optionally overcoated with a barrier agent, to separate the
therapeutically active agent from the hydrophobic controlled
release coating. An example of a suitable barrier agent is one
which comprises hydroxypropylmethylcellulose. However, any
film-former known in the art may be used. It is preferred that the
barrier agent does not affect the dissolution rate of the final
product.
[0101] The beads may then be overcoated with an aqueous dispersion
of the hydrophobic material. The aqueous dispersion of hydrophobic
material preferably further includes an effective amount of
plasticizer, e.g. triethyl citrate. Pre-formulated aqueous
dispersions of ethylcellulose, such as Aquacoat.RTM. or
Surelease.RTM., may be used. If Surelease.RTM. is used, it is not
necessary to separately add a plasticizer. Alternatively,
pre-formulated aqueous dispersions of acrylic polymers such as
Eudragit.RTM. can be used.
[0102] The coating solutions of the present invention preferably
contain, in addition to the film-former, plasticizer, and solvent
system (i.e., water), a colorant to provide elegance and product
distinction. Color may be added to the solution of the
therapeutically active agent instead, or in addition to the aqueous
dispersion of hydrophobic material. For example, color may be added
to Aquacoat.TM. via the use of alcohol or propylene glycol based
color dispersions, milled aluminum lakes and opacifiers such as
titanium dioxide by adding color with shear to water soluble
polymer solution and then using low shear to the plasticized
Aquacoat.RTM.. Alternatively, any suitable method of providing
color to the formulations of the present invention may be used.
Suitable ingredients for providing color to the formulation when an
aqueous dispersion of an acrylic polymer is used include titanium
dioxide and color pigments, such as iron oxide pigments. The
incorporation of pigments, may, however, increase the retard effect
of the coating.
[0103] Plasticized hydrophobic material may be applied onto the
substrate comprising the therapeutically active agent by spraying
using any suitable spray equipment known in the art. In a preferred
method, a Wurster fluidized-bed system is used in which an air jet,
injected from underneath, fluidizes the core material and effects
drying while the acrylic polymer coating is sprayed on. A
sufficient amount of the hydrophobic material to obtain a
predetermined controlled release of said therapeutically active
agent when the coated substrate is exposed to aqueous solutions,
e.g. gastric fluid, is preferably applied, taking into account the
physical characteristics of the therapeutically active agent, the
manner of incorporation of the plasticizer, etc. After coating with
the hydrophobic material, a further overcoat of a film-former, such
as Opadry.RTM., is optionally applied to the beads. This overcoat
is provided, if at all, in order to substantially reduce
agglomeration of the beads.
[0104] The release of the therapeutically active agent from the
controlled release formulation of the present invention can be
further influenced, i.e., adjusted to a desired rate, by the
addition of one or more release-modifying agents, or by providing
one or more passageways through the coating. The ratio of
hydrophobic material to water soluble material is determined by,
among other factors, the release rate required and the solubility
characteristics of the materials selected.
[0105] The release-modifying agents which function as pore-formers
may be organic or inorganic, and include materials that can be
dissolved, extracted or leached from the coating in the environment
of use. The pore-formers may comprise one or more hydrophilic
materials such as hydroxypropylmethylcellulose.
[0106] The sustained release coatings of the present invention can
also include erosion-promoting agents such as starch and gums.
[0107] The sustained release coatings of the present invention can
also include materials useful for making microporous lamina in the
environment of use, such as polycarbonates comprised of linear
polyesters of carbonic acid in which carbonate groups reoccur in
the polymer chain.
[0108] The release-modifying agent may also comprise a
semi-permeable polymer.
[0109] In certain preferred embodiments, the release-modifying
agent is selected from hydroxypropylmethylcellulose, lactose, metal
stearates, and mixtures of any of the foregoing.
[0110] The sustained release coatings of the present invention may
also include an exit means comprising at least one passageway,
orifice, or the like. The passageway may be formed by such methods
as those disclosed in U.S. Pat. Nos. 3,845,770; 3,916,889;
4,063,064; and 4,088,864 (all of which are hereby incorporated by
reference). The passageway can have any shape such as round,
triangular, square, elliptical, irregular, etc.
Matrix Bead Formulations
[0111] In other embodiments of the present invention, the
controlled release formulation is achieved via a matrix having a
controlled release coating as set forth above. The present
invention may also utilize a controlled release matrix that affords
in-vitro dissolution rates of the opioid within the preferred
ranges and that releases the opioid in a pH-dependent or
pH-independent manner. The materials suitable for inclusion in a
controlled release matrix will depend on the method used to form
the matrix.
[0112] For example, a matrix in addition to the opioid analgesic
and (optionally) COX-2 may include:
[0113] Hydrophilic and/or hydrophobic materials, such as gums,
cellulose ethers, acrylic resins, protein derived materials; the
list is not meant to be exclusive, and any pharmaceutically
acceptable hydrophobic material or hydrophilic material which is
capable of imparting controlled release of the active agent and
which melts (or softens to the extent necessary to be extruded) may
be used in accordance with the present invention.
[0114] Digestible, long chain (C.sub.8-C.sub.50, especially
C.sub.12-C.sub.40), substituted or unsubstituted hydrocarbons, such
as fatty acids, fatty alcohols, glyceryl esters of fatty acids,
mineral and vegetable oils and waxes, and stearyl alcohol; and
polyalkylene glycols.
[0115] Of these polymers, acrylic polymers, especially
Eudragit.RTM. RSPO--the cellulose ethers, especially
hydroxyalkylcelluloses and carboxyalkylcelluloses, are preferred.
The oral dosage form may contain between 1% and 80% (by weight) of
at least one hydrophilic or hydrophobic material.
[0116] When the hydrophobic material is a hydrocarbon, the
hydrocarbon preferably has a melting point of between 25.degree.
and 90.degree. C. Of the long chain hydrocarbon materials, fatty
(aliphatic) alcohols are preferred. The oral dosage form may
contain up to 60% (by weight) of at least one digestible, long
chain hydrocarbon.
[0117] Preferably, the oral dosage form contains up to 60% (by
weight) of at least one polyalkylene glycol.
[0118] The hydrophobic material is preferably selected from the
group consisting of alkylcelluloses, acrylic and methacrylic acid
polymers and copolymers, shellac, zein, hydrogenated castor oil,
hydrogenated vegetable oil, or mixtures thereof. In certain
preferred embodiments of the present invention, the hydrophobic
material is a pharmaceutically acceptable acrylic polymer,
including but not limited to acrylic acid and methacrylic acid
copolymers, methyl methacrylate, methyl methacrylate copolymers,
ethoxyethyl methacrylates, cyano ethyl methacrylate, aminoalkyl
methacrylate copolymer, poly(acrylic acid), poly(methacrylic acid),
methacrylic acid alkylamine copolymer, poly(methyl methacrylate),
poly(methacrylic acid)(anhydride), polymethacrylate,
polyacrylamide, poly(methacrylic acid anhydride), and glycidyl
methacrylate copolymers. In other embodiments, the hydrophobic
material is selected from materials such as hydroxyalkylcelluloses
such as hydroxypropylmethylcellulose and mixtures of the
foregoing.
[0119] Preferred hydrophobic materials are water-insoluble with
more or less pronounced hydrophilic and/or hydrophobic trends.
Preferably, the hydrophobic materials useful in the invention have
a melting point from about 30.degree. to about 200.degree. C.,
preferably from about 45.degree. C. to about 90.degree. C.
Specifically, the hydrophobic material may comprise natural or
synthetic waxes, fatty alcohols (such as lauryl, myristyl, stearyl,
cetyl or preferably cetostearyl alcohol), fatty acids, including
but not limited to fatty acid esters, fatty acid glycerides (mono-,
di-, and tri-glycerides), hydrogenated fats, hydrocarbons, normal
waxes, stearic aid, stearyl alcohol and hydrophobic and hydrophilic
materials having hydrocarbon backbones. Suitable waxes include, for
example, beeswax, glycowax, castor wax and carnauba wax. For
purposes of the present invention, a wax-like substance is defined
as any material which is normally solid at room temperature and has
a melting point of from about 30.degree. to about 100.degree.
C.
[0120] Suitable hydrophobic materials which may be used in
accordance with the present invention include digestible, long
chain (C.sub.8-C.sub.50, especially C.sub.12-C.sub.40), substituted
or unsubstituted hydrocarbons, such as fatty acids, fatty alcohols,
glyceryl esters of fatty acids, mineral and vegetable oils and
natural and synthetic waxes. Hydrocarbons having a melting point of
between 25.degree. and 90.degree. C. are preferred. Of the long
chain hydrocarbon materials, fatty (aliphatic) alcohols are
preferred in certain embodiments. The oral dosage form may contain
up to 60% (by weight) of at least one digestible, long chain
hydrocarbon.
[0121] Preferably, a combination of two or more hydrophobic
materials are included in the matrix formulations. If an additional
hydrophobic material is included, it is preferably selected from
natural and synthetic waxes, fatty acids, fatty alcohols, and
mixtures of the same. Examples include beeswax, carnauba wax,
stearic acid and stearyl alcohol. This list is not meant to be
exclusive.
[0122] One particular suitable matrix comprises at least one water
soluble hydroxyalkyl cellulose, at least one C.sub.12-C.sub.36,
preferably C.sub.14-C.sub.22, aliphatic alcohol and, optionally, at
least one polyalkylene glycol. The at least one hydroxyalkyl
cellulose is preferably a hydroxy (C.sub.1 to C.sub.6) alkyl
cellulose, such as hydroxypropylcellulose,
hydroxypropylmethylcellulose and, especially,
hydroxyethylcellulose. The amount of the at least one hydroxyalkyl
cellulose in the present oral dosage form will be determined, inter
alia, by the precise rate of opioid release required. The at least
one aliphatic alcohol may be, for example, lauryl alcohol, myristyl
alcohol or stearyl alcohol. In particularly preferred embodiments
of the present oral dosage form, however, the at least one
aliphatic alcohol is cetyl alcohol or cetostearyl alcohol. The
amount of the at least one aliphatic alcohol in the present oral
dosage form will be determined, as above, by the precise rate of
opioid release required. It will also depend on whether at least
one polyalkylene glycol is present in or absent from the oral
dosage form. In the absence of at least one polyalkylene glycol,
the oral dosage form preferably contains between 20% and 50% (by
wt) of the at least one aliphatic alcohol. When at least one
polyalkylene glycol is present in the oral dosage form, then the
combined weight of the at least one aliphatic alcohol and the at
least one polyalkylene glycol preferably constitutes between 20%
and 50% (by wt) of the total dosage.
[0123] In one embodiment, the ratio of, e.g., the at least one
hydroxyalkyl cellulose or acrylic resin to the at least one
aliphatic alcohol/polyalkylene glycol determines, to a considerable
extent, the release rate of the opioid from the formulation. A
ratio of the at least one hydroxyalkyl cellulose to the at least
one aliphatic alcohol/polyalkylene glycol of between 1:2 and 1:4 is
preferred, with a ratio of between 1:3 and 1:4 being particularly
preferred.
[0124] The at least one polyalkylene glycol may be, for example,
polypropylene glycol or, which is preferred, polyethylene glycol.
The number average molecular weight of the at least one
polyalkylene glycol is preferred between 1,000 and 15,000
especially between 1,500 and 12,000.
[0125] Another suitable controlled release matrix would comprise an
alkylcellulose (especially ethyl cellulose), a C.sub.12 to C.sub.36
aliphatic alcohol and, optionally, a polyalkylene glycol.
[0126] In another preferred embodiment, the matrix includes a
pharmaceutically acceptable combination of at least two hydrophobic
materials.
[0127] In addition to the above ingredients, a controlled release
matrix may also contain suitable quantities of other materials,
e.g. diluents, lubricants, binders, granulating aids, colorants,
flavorants and glidants that are conventional in the pharmaceutical
art.
Process for Preparing Matrix-Based Beads
[0128] In order to facilitate the preparation of a solid,
controlled release, oral dosage form according to this invention,
any method of preparing a matrix formulation known to those skilled
in the art may be used. For example incorporation in the matrix may
be effected, for example, by (a) forming granules comprising at
least one water soluble hydroxyalkyl cellulose and opioid or an
opioid salt; (b) mixing the hydroxyalkyl cellulose containing
granules with at least one C.sub.12-C.sub.36 aliphatic alcohol; and
(c) optionally, compressing and shaping the granules. Preferably,
the granules are formed by wet granulating the hydroxyalkyl
cellulose/opioid with water. In a particularly preferred embodiment
of this process, the amount of water added during the wet
granulation step is preferably between 1.5 and 5 times, especially
between 1.75 and 3.5 times, the dry weight of the opioid.
[0129] In yet other alternative embodiments, a spheronizing agent,
together with the active ingredient can be spheronized to form
spheroids. Microcrystalline cellulose is preferred. A suitable
microcrystalline cellulose is, for example, the material sold as
Avicel PH 101 (Trade Mark, FMC Corporation). In such embodiments,
in addition to the active ingredient and spheronizing agent, the
spheroids may also contain a binder. Suitable binders, such as low
viscosity, water soluble polymers, will be well known to those
skilled in the pharmaceutical art. However, water soluble hydroxy
lower alkyl cellulose, such as hydroxypropylcellulose, are
preferred. Additionally (or alternatively) the spheroids may
contain a water insoluble polymer, especially an acrylic polymer,
an acrylic copolymer, such as a methacrylic acid-ethyl acrylate
copolymer, or ethyl cellulose. In such embodiments, the sustained
release coating will generally include a hydrophobic material such
as (a) a wax, either alone or in admixture with a fatty alcohol; or
(b) shellac or zein.
[0130] Melt Extrusion Matrix
[0131] Sustained release matrices can also be prepared via
melt-granulation or melt-extrusion techniques. Generally,
melt-granulation techniques involve melting a normally solid
hydrophobic material, e.g. a wax, and incorporating a powdered drug
therein. To obtain a sustained release dosage form, it may be
necessary to incorporate an additional hydrophobic substance, e.g.
ethylcellulose or a water-insoluble acrylic polymer, into the
molten wax hydrophobic material. Examples of sustained release
formulations prepared via melt-granulation techniques are found in
U.S. Pat. No. 4,861,598, assigned to the Assignee of the present
invention and hereby incorporated by reference in its entirety.
[0132] The additional hydrophobic material may comprise one or more
water-insoluble wax-like thermoplastic substances possibly mixed
with one or more wax-like thermoplastic substances being less
hydrophobic than said one or more water-insoluble wax-like
substances. In order to achieve constant release, the individual
wax-like substances in the formulation should be substantially
non-degradable and insoluble in gastrointestinal fluids during the
initial release phases. Useful water-insoluble wax-like substances
may be those with a water-solubility that is lower than about
1:5,000 (w/w).
[0133] In addition to the above ingredients, a sustained release
matrix may also contain suitable quantities of other materials,
e.g., diluents, lubricants, binders, granulating aids, colorants,
flavorants and glidants that are conventional in the pharmaceutical
art. The quantities of these additional materials will be
sufficient to provide the desired effect to the desired
formulation. In addition to the above ingredients, a sustained
release matrix incorporating melt-extruded multiparticulates may
also contain suitable quantities of other materials, e.g. diluents,
lubricants, binders, granulating aids, colorants, flavorants and
glidants that are conventional in the pharmaceutical art in amounts
up to about 50% by weight of the particulate if desired.
[0134] Specific examples of pharmaceutically acceptable carriers
and excipients that may be used to formulate oral dosage forms are
described in the Handbook of Pharmaceutical Excipients, American
Pharmaceutical Association, (1986), incorporated by reference
herein.
[0135] Melt Extrusion Multiparticulates
[0136] The preparation of a suitable melt-extruded matrix according
to the present invention may, for example, include the steps of
blending the opioid analgesic, together with at least one
hydrophobic material and preferably the additional hydrophobic
material to obtain a homogeneous mixture. The homogeneous mixture
is then heated to a temperature sufficient to at least soften the
mixture sufficiently to extrude the same. The resulting homogeneous
mixture is then extruded to form strands. The extrudate is
preferably cooled and cut into multiparticulates by any means known
in the art. The strands are cooled and cut into multiparticulates.
The multiparticulates are then divided into unit doses. The
extrudate preferably has a diameter of from about 0.1 to about 5 mm
and provides sustained release of the therapeutically active agent
for a time period of from about 8 to about 24 hours.
[0137] An optional process for preparing the melt extrusions of the
present invention includes directly metering into an extruder a
hydrophobic material, a therapeutically active agent, and an
optional binder; heating the homogenous mixture; extruding the
homogenous mixture to thereby form strands; cooling the strands
containing the homogeneous mixture; cutting the strands into
particles having a size from about 0.1 mm to about 12 mm; and
dividing said particles into unit doses. In this aspect of the
invention, a relatively continuous manufacturing procedure is
realized.
[0138] The diameter of the extruder aperture or exit port can also
be adjusted to vary the thickness of the extruded strands.
Furthermore, the exit part of the extruder need not be round; it
can be oblong, rectangular, etc. The exiting strands can be reduced
to particles using a hot wire cutter, guillotine, etc.
[0139] The melt extruded multiparticulate system can be, for
example, in the form of granules, spheroids or pellets depending
upon the extruder exit orifice. For purposes of the present
invention, the terms "melt-extruded multiparticulate(s)" and
"melt-extruded multiparticulate system(s)" and "melt-extruded
particles" shall refer to a plurality of units, preferably within a
range of similar size and/or shape and containing one or more
active agents and one or more excipients, preferably including a
hydrophobic material as described herein. In this regard, the
melt-extruded multiparticulates will be of a range of from about
0.1 to about 12 mm in length and have a diameter of from about 0.1
to about 5 mm. In addition, it is to be understood that the
melt-extruded multiparticulates can be any geometrical shape within
this size range. Alternatively, the extrudate may simply be cut
into desired lengths and divided into unit doses of the
therapeutically active agent without the need of a spheronization
step.
[0140] In one preferred embodiment, oral dosage forms are prepared
to include an effective amount of melt-extruded multiparticulates
within a capsule. For example, a plurality of the melt-extruded
multiparticulates may be placed in a gelatin capsule in an amount
sufficient to provide an effective sustained release dose when
ingested and contacted by gastric fluid.
[0141] In another preferred embodiment, a suitable amount of the
multiparticulate extrudate is compressed into an oral tablet using
conventional tableting equipment using standard techniques.
Techniques and compositions for making tablets (compressed and
molded), capsules (hard and soft gelatin) and pills are also
described in Remington's Pharmaceutical Sciences, (Arthur Osol,
editor), 1553-1593 (1980), incorporated by reference herein.
[0142] In yet another preferred embodiment, the extrudate can be
shaped into tablets as set forth in U.S. Pat. No. 4,957,681
(Klimesch, et. al.), described in additional detail above and
hereby incorporated by reference.
[0143] Optionally, the sustained release melt-extruded
multiparticulate systems or tablets can be coated, or the gelatin
capsule can be further coated, with a sustained release coating
such as the sustained release coatings described above. Such
coatings preferably include a sufficient amount of hydrophobic
material to obtain a weight gain level from about 2 to about 30
percent, although the overcoat may be greater depending upon the
physical properties of the particular opioid analgesic compound
utilized and the desired release rate, among other things.
[0144] The melt-extruded unit dosage forms of the present invention
may further include combinations of melt-extruded multiparticulates
containing one or more of the therapeutically active agents
disclosed above before being encapsulated. Furthermore, the unit
dosage forms can also include an amount of an immediate release
therapeutically active agent for prompt therapeutic effect. The
immediate release therapeutically active agent may be incorporated,
e.g., as separate pellets within a gelatin capsule, or may be
coated on the surface of the multiparticulates after preparation of
the dosage forms (e.g., controlled release coating or
matrix-based). The unit dosage forms of the present invention may
also contain a combination of controlled release beads and matrix
multiparticulates to achieve a desired effect.
[0145] The sustained release formulations of the present invention
preferably slowly release the therapeutically active agent, e.g.,
when ingested and exposed to gastric fluids, and then to intestinal
fluids. The sustained release profile of the melt-extruded
formulations of the invention can be altered, for example, by
varying the amount of retardant, i.e., hydrophobic material, by
varying the amount of plasticizer relative to hydrophobic material,
by the inclusion of additional ingredients or excipients, by
altering the method of manufacture, etc.
[0146] In other embodiments of the invention, the melt extruded
material is prepared without the inclusion of the therapeutically
active agent, which is added thereafter to the extrudate. Such
formulations typically will have the therapeutically active agent
blended together with the extruded matrix material, and then the
mixture would be tableted in order to provide a slow release
formulation. Such formulations may be advantageous, for example,
when the therapeutically active agent included in the formulation
is sensitive to temperatures needed for softening the hydrophobic
material and/or the retardant material.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0147] The following examples illustrate various aspects of the
present invention. They are not to be construed to limit the claims
in any manner whatsoever.
EXAMPLE 1
[0148] The separability of Naltrexone Hydrochloride from
Hydrocodone Bitartrate using an extraction procedure mimicking that
of a drug abuser is examined. Inspection of the structures and
consideration of the pKa's (FIG. 1) would suggest that both
compounds would be soluble in acid. However, Naltrexone should also
be very soluble at high pH's with a minimum solubility between pH
8.4 and 10.3. We wanted to test the hypothesis that both compounds
could be extracted from a tablet in acid and then the Hydrocodone
could be precipitated out by high pH.
[0149] Since Hydrocodone controlled release tablets (HYCR) and
Naltrexone tablets were not available for this study, simulated
samples were prepared by adding known amounts of Hydrocodone
Bitartrate and Naltrexone Hydrochloride drug substances to HYCR
AcroContin 15 mg tablets placebo ("Acrocontin" refers to a
proprietary controlled release base comprising an ammonio
methacrylate polymer together with a higher aliphatic alcohol, as
described for example in U.S. Pat. No. 4,861,598, hereby
incorporated by reference) Different solvents of varying pH's were
used to extract Hydrocodone Bitartrate and/or Naltrexone HCl at
concentrations of 4 tablets/25 mL (section 2.1) and 5 tablets/5 mL
(section 2.2) of solvent. The recoveries were quantitated using
HPLC.
[0150] 2.1 Extraction at Concentrations of 4 Tablets in 25 mL of
Solvent
[0151] 2.1.1 About 60 mg of Hydrocodone bitartrate, 25 mg of
Naltrexone hydrochloride and 400 mg of HYCR 15 mg AcroContin
tablets placebo (equivalent to 4 tablets) were added to a 25 mL
volumetric flask. About 15 mL of water was added into the
volumetric flask and the solution was sonicated for 10 minutes. The
solution was diluted to volume with water and mixed well. This was
the sample stock solution. Thirteen sample stock solutions were
prepared in this manner.
[0152] 2.1.2 The pH of the solutions were then adjusted with either
glacial acetic acid or 0.2N NaOH to pH 2.0, 4.0, 5.1, 6.0, 6.5,
7.0, 7.4, 8.0, 8,5, 9.0, 9,4, and 10.0. However, in preparing the
pH 1.1 solution, hydrochloric acid was used. Then step 2.1.4. was
followed.
[0153] 2.1.3 Step 2.1.1 of the procedure was repeated to prepare
sample stock solutions in ethanol, methanol and acetone instead of
water.
[0154] 2.1.4 Each solution was filtered using a 5 mL disposable
syringe and a Millex-HV 0.45 .mu.m filter unit. 1.0 mL of the clear
filtrate was pipetted into a 25 mL volumetric flask, diluted to
volume with water and mixed well. The sample solutions were then
injected onto the HPLC system and the results are presented in
Table 1.
[0155] 2.2 Extraction at Concentrations of 5 Tablets in 5 mL of
Solvent
[0156] 2.2.1 About 75 mg of Hydrocodone bitartrate and 32 mg of
Naltrexone hydrochloride were added to a scintillation vial which
contained 475 mg of HYCR 15 mg AcroContin tablets placebo
(equivalent to 5 tablets). 5.0 mL of water was added into the
scintillation via and the solution was sonicated for 10 minutes.
This was the sample stock solution.
[0157] 2.2.2 The solution's pH was then adjusted with 50% w/w NaOH
to pH 7.1. After the solution settled for one hour, the entire
solution was filtered using a 5 mL disposable syringe and a
Millex-HV 0.45 .mu.m filter unit. 1.0 mL of this clear filtrate was
pipetted into a 25 mL volumetric flask, diluted to volume with
water, and mixed well. This was the pH 7.1 sample stock
solution.
[0158] 2.2.3 Steps 2.2.1 and 2.2.2 of the procedure was repeated to
prepare the sample solutions at pH 8.0, 9.0, 10.0, 11.0, 12.0 and
12.7. The samples solutions were then injected onto the HPLC system
and the results are present in Table 2.
RESULTS
[0159] The results are presented in Table 1 and 2. In Table 2, it
is noted that both Hydrocodone and Naltrexone dissolved completely
in all of the solvents except acetone. In Table 2, it is noted that
the amount of Naltrexone retained in the solution decreased at pH 8
and increased again at pH 10 and the Hydrocodone retained in the
solution decreased at higher pH.
4TABLE 1 Simulated Extractability of Naltrexone Hydrochloride from
Hydrocodone Bitartrate CR 15 mg AcroContin Tablets at Concentration
of 4 Tablets in 25 mL of Solvent. % Recovery Sample # Diluent
Naltrexone Hydrocodone 1 pH 1.1 101 101 2 pH 3.0 102 101 3 pH 4.0
100 100 4 pH 5.1 102 100 5 pH 6.0 102 100 6 pH 6.5 99 99 7 pH 7.0
100 100 8 pH 7.4 100 101 9 pH 8.0 102 99 10 pH 8.5 99 100 11 pH 9.0
99 99 12 pH 9.4 100 100 13 pH 10.0 97 99 14 Ethanol 116 89 15
Methanol 106 102 16 Acetone 35 21
[0160]
5TABLE 2 Simulated Extractability of Naltrexone Hydrochloride from
Hydrocodone Bitartrate CR 15 mg AcroContin Tablets at Concentration
of 5 Tablets in 5 mL of Solvent. % Recovery % Precipitated Sample #
Diluent Naltrexone Hydrocodone Hydrocodone 1 pH 7.1 92 92 8 2 pH
8.0 84 88 12 3 pH 9.0 46 73 27 4 pH 10.0 49 72 28 5 pH 11.0 70 79
21 6 pH 12.0 88 17 83 7 pH 12.7 87 19 81
[0161] FIG. 1 provides structures and pKa Values of Hydrocodone and
Naltrexone Base.
CONCLUSIONS
[0162] In Table 1, it can be observed that the concentrations of
Hydrocodone and Naltrexone were too low in 25 mL of solvents and
they dissolved almost completely in varying pH's as well as in
ethanol and methanol. In acetone, Hydrocodone and Naltrexone are
less soluble and poor recoveries were obtained.
[0163] In Table 2, the results can be explained by examining the
pKa's of the drug substances. The pKa values of Naltrexone
Hydrochloride which were obtained in PRC, Yonkers are 8.4 (at amine
functional group) and 10.3 (at phenol functional group) and the pKa
value of Hydrocodone Bitartrate (at amine functional group) is 9.2.
The chemical structures and pKa values of Hydrocodone and
Naltrexone base are shown in FIG. 1.
[0164] For Naltrexone Hydrochloride: As the pH reaches 8.4, the
Naltrexone becomes the free base form and starts precipitating out
of the solution and when the pH reaches 10.3, the phenolic OH
functional group deionizes and the compound dissolves again into
the solution. For Hydrocodone Bitartrate: The Hydrocodone becomes
free base at pH higher than 9.2 and starts to precipitate out of
the solution.
[0165] Table 1 shows that about 80% of Hydrocodone Bitartrate and
10% of Naltrexone Hydrochloride might be extractable from the
tablets at the higher pH's.
[0166] This procedure would probably not be that easy on the
street. Both strong acid and strong base would be required plus
grinding and filtering steps. Moreover, the recovered hydrocodone
is soaked with strong caustic, any attempt to wash off the caustic
would result in some loss of hydrocodone.
[0167] However, it is important to note that in this wet recovery
experiment, neither drug was incorporated into the tablet matrix
through the manufacturing procedure (hot wax). It is most likely
that from an actual tablet the recoveries could be worse.
Additionally, the addition of a gelling agent or other excipients
could make it even more difficult.
EXAMPLE 2
[0168] Extractability of Nalterexone Hydrochloride (1.5 mg) from
Hydromorphone Hydrochoride (15 mg) at a concentration of 5
tablets/5 mL of solvent is studied, using the same techniques set
forth in Example 1. The results are provided in Table 3 below:
6 TABLE 3 % Recovery Hydro- % Precipitated Sample # Diluent
Naltrexone morphone Hydromorphone 1 pH 7.2 95 95 5 2 pH 7.9 88 91 9
3 pH 9.0 79 90 10 4 pH 9.9 79 90 10 5 pH 11.0 79 89 11 6 pH 11.9 84
88 12 7 pH 12.9 69 73 27 8 Methanol 96 66 34 9 Ethanol 97 32 68 10
IPA 90 1 99
EXAMPLE 3
[0169] The extractability of Nalterexone Hydrochloride (1.5 mg)
from Oxycodone Hydrochoride (15 mg) at a concentration of 5
tablets/5 mL of solvent is studied, using the same techniques set
forth in Example 1. The results are provided in Table 4 below:
7 TABLE 4 % Recovery % Precipitated Sample # Diluent Naltrexone
Oxycodone Oxycodone 1 pH 6.9 101 94 6 2 pH 8.1 80 13 87 3 pH 9.4 62
2 98 4 pH 10.2 58 2 98 5 pH 11.0 78 2 98 6 pH 11.9 68 2 98 7 pH
12.8 76 2 98 8 Methanol 78 87 13 9 Ethanol 74 87 13 10 IPA 70 14
86
[0170] While the invention has been described and illustrated with
reference to certain preferred embodiments thereof, those skilled
in the art will appreciate that obvious modifications can be made
herein without departing from the spirit and scope of the
invention. Such variations are contemplated to be within the scope
of the appended claims.
* * * * *