U.S. patent application number 10/679581 was filed with the patent office on 2004-10-07 for novel microemulsion and micelle systems for solubilizing drugs.
This patent application is currently assigned to University of Florida Research Foundation, Incorporated. Invention is credited to Dennis, Donn M., Gravenstein, Nikolaus, Modell, Jerome H., Morey, Timothy E., Shah, Dinesh.
Application Number | 20040198813 10/679581 |
Document ID | / |
Family ID | 24526357 |
Filed Date | 2004-10-07 |
United States Patent
Application |
20040198813 |
Kind Code |
A1 |
Dennis, Donn M. ; et
al. |
October 7, 2004 |
Novel microemulsion and micelle systems for solubilizing drugs
Abstract
A microemulsion delivery system for water insoluble or sparingly
water soluble drugs that comprises a long polymer chain surfactant
component and a short fatty acid surfactant component, with the
amount of each being selected to provide stable microemulsion or
micellar systems.
Inventors: |
Dennis, Donn M.;
(Gainesville, FL) ; Gravenstein, Nikolaus;
(Gainesville, FL) ; Modell, Jerome H.;
(Gainesville, FL) ; Morey, Timothy E.;
(Gainesville, FL) ; Shah, Dinesh; (Gainesville,
FL) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Assignee: |
University of Florida Research
Foundation, Incorporated
|
Family ID: |
24526357 |
Appl. No.: |
10/679581 |
Filed: |
October 6, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10679581 |
Oct 6, 2003 |
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09924290 |
Aug 8, 2001 |
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6638537 |
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09924290 |
Aug 8, 2001 |
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09630237 |
Aug 1, 2000 |
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6623765 |
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Current U.S.
Class: |
514/499 |
Current CPC
Class: |
A61K 9/1075
20130101 |
Class at
Publication: |
514/499 |
International
Class: |
A61K 031/30 |
Claims
1-24. Cancelled
25. A microemulsion composition for intravenous delivery comprising
an oil phase and an aqueous phase, wherein the oil phase comprises:
an oil-soluble drug; a long chain polymer surfactant component; and
a short chain fatty acid surfactant component; and wherein the
amounts of the long chain polymer and short chain fatty acid
surfactant components are selected to provide for spontaneous
formation of thermodynamically stable microemulsion droplets of the
oil phase having a particle size from 10 nm to 100 nm.
26. The composition of claim 25, wherein the oil-soluble drug is a
solid.
27. The composition of claim 26, wherein the long chain polymer
surfactant component is selected from the group consisting of
polyoxyethylene alkyl esters, polyoxyethylene glycols,
polyvinylpyrrolidone, polyvinylalcohol, tyloxapol, and
poloxamer.
28. The composition of claim 27, wherein the long chain polymer
surfactant component is a poloxamer.
29. The composition of claim 26, wherein the short chain fatty acid
surfactant component is a C.sub.8 to C.sub.16 component.
30. The composition of claim 29, wherein the short chain fatty acid
surfactant component is a C.sub.8 to C.sub.12 component.
31. The composition of claim 26, wherein the long chain polymer
surfactant component is a poloxamer and the short chain fatty acid
surfactant component is a laurate.
32. The composition of claim 26, wherein the total amount of long
chain polymer surfactant component and short chain fatty acid
surfactant component does not exceed 4.65% by weight.
33. The composition of claim 26, wherein the interfacial tension of
the oil-soluble drug with an emulsifier combination comprising the
long chain polymer surfactant component and the short chain fatty
acid surfactant component is less than 0.1 dynes per cm.
34. The composition of claim 26, wherein the oil-soluble drug is
selected from the group consisting of analgesics, anesthetics,
antibiotics, antidepressants, antidiabetics, antifungals,
antihypertensives, anti-inflammatories, antineoplastics,
immunosuppressives, sedatives, antianginals, antipsychotics,
antimanics, antiarthritics, antigouts, anticoagulants,
antithrombolytics, anticonvulsants, antiparkinsons, antibacterials,
antivirals, and anti-infectives.
35. The composition of claim 34, wherein the oil-soluble drug is an
anesthetic.
36. The composition of claim 35, wherein the oil-soluble drug is an
aryl containing molecule.
37. The composition of claim 25, wherein the oil-soluble drug is an
oil-soluble vitamin.
38. The composition of claim 26, wherein the long chain polymer
surfactant component and the short chain fatty acid surfactant
component are selected from the GRAS list.
39. The composition of claim 26, wherein the ratio of long chain
polymer surfactant component to short chain fatty acid surfactant
component is from 10:100 to 25:80 wt/wt.
40. The composition of claim 26, wherein the long chain polymer
surfactant component has a molecular weight greater than 1000, and
the short chain fatty acid surfactant component has a molecular
weight less than 1000.
41. The composition of claim 39, wherein the amount of oil-soluble
drug is from 0.1% to 1.0%.
42. The composition of claim 26, wherein the oil-soluble drug is a
mixture of the base form and the salt form of the drug.
43. The composition of claim 26, wherein the drug transfer rate is
controlled by control of the character and nature of micelle
formation of the microemulsion droplets.
44. A method of controlling intravenous drug delivery and transfer
rate of an oil-soluble drug comprising: administering a composition
comprising microdroplets of the oil-soluble drug and an emulsifier
combination comprising a long chain polymer surfactant component
and a short chain fatty acid surfactant component, the amounts of
each component being selected to provide for spontaneous formation
of thermodynamically stable microemulsion droplets having a
particle size from 10 nm to 100 nm and to control intravenous
delivery and transfer rate as desired.
45. A microemulsion composition for drug delivery comprising an oil
phase and an aqueous phase, wherein the oil phase comprises: an
oil-soluble drug; and an emulsifier combination comprising a long
chain polymer surfactant component and a short chain fatty acid
surfactant component; and wherein the amounts of the long chain
polymer surfactant component and the short chain fatty acid
surfactant component are selected to provide for spontaneous
formation of thermodynamically stable microemulsion droplets of the
oil phase having a particle size from 10 nm to 100 nm and wherein
the interfacial tension of the oil-soluble drug with the emulsifier
combination is less than 0.1 dynes per cm.
46. The method of claim 44, wherein the oil-soluble drug is a
solid.
47. The microemulsion composition of claim 25 comprising at least
two oil-soluble drugs.
Description
CROSS REFERENCED TO A RELATED APPLICATION
[0001] This application is a continuation-in-part of Dennis et al.,
Ser. No. 09/630,237 filed Aug. 1, 2000.
FIELD OF THE INVENTION
[0002] This invention relates to compositions and a method for
making microemulsion delivery systems for water insoluble or
sparingly soluble drugs.
BACKGROUND OF THE INVENTION
[0003] Dissolving water insoluble agents into aqueous solutions
appropriate for human use (e.g., oral, topical application,
intravenous injection, intramuscular injection, subcutaneous
injection) represents a major technological hurdle for
pharmaceutical delivery systems. Previous attempts have resulted in
a number of serious side effects caused not by the drugs, but by
the carrier agents used to dissolve the drug. These complications
include significant hypotension during intravenous injection (e.g.,
amiodarone), painful injection with subsequent phlebitis (e.g.,
valium), anaphylaxis (e.g., propofol in Cremaphor), postoperative
infections (e.g., propofol in Intralipid), and others. Clearly, an
approach aimed at improving the solubilization of these drugs and
avoiding the complications of solubilizing agents would enhance the
quality of health care to patients. For many drugs, a major
technological barrier for their routine clinical use is very poor
solubility in the aqueous phase. For such drugs, oil/water
macroemulsions have been commonly used in the pharmaceutical
industry to "dissolve" a drug to its desired concentration. For
example, the anesthetic propofol is supplied to the health care
industry as Baxter PPI propofol (Gensia Sicor, Inc.) or Diprivan
(AstraZeneca Pharmaceuticals, Inc.), as a macroemulsion of propofol
in soybean oil (100 mg/mL), glycerol (22.5 mg/mL), egg lecithin (12
mg/mL), and disodium edetate (0.005%) or metabisulfite; with sodium
hydroxide to adjust pH to 7.0-8.5. However, the stability of such
macroemulsions is relatively poor, and the oil and water components
separate into distinct phases over time. In addition, the droplet
size of the macroemulsion increases with time. Macroemulsions are
defined as formed by high shear mixing and normally having
particles of 1 micron to 10 microns in size.
[0004] In contrast to macroemulsion systems, microemulsion systems
consisting of oil, water, and appropriate emulsifiers can form
spontaneously and are therefore thermodynamically stable. For this
reason, microemulsion systems theoretically have an infinite shelf
life under normal conditions in contrast to the limited life of
macroemulsions (e.g., two years for Baxter PPI propofol). In
addition, the size of the droplets in such microemulsions remains
constant and ranges from 100-1000 angstroms (10-100 nm), and has
very low oil/water interfacial tension. Because the droplet size is
less than 25% of the wavelength of visible light, microemulsions
are transparent. Three distinct microemulsion solubilization
systems that can be used for drugs are as follows:
[0005] 1. oil in water microemulsions wherein oil droplets are
dispersed in the continuous aqueous phase;
[0006] 2. water in oil microemulsions wherein water droplets are
dispersed in the continuous oil phase;
[0007] 3. bi-continuous microemulsions wherein microdomains of oil
and water are interdispersed within the system. In all three types
of microemulsions, the interface is stabilized by an appropriate
combination of surfactants and/or co-surfactants.
[0008] It can be seen from the above description that there is a
real and continuing need for the development of new and effective
drug delivery systems for water insoluble or sparingly soluble
drugs. One such approach might be pharmaceutical microemulsions.
However, one must choose materials that are biocompatible,
non-toxic, clinically acceptable, and use emulsifiers in an
appropriate concentration range, and form stable microemulsions.
This invention has as its objective the formation of safe and
effective pharmaceutical microemulsion delivery systems.
[0009] The delivery system described herein has been found
particularly useful for propofol, but is not exclusively limited
thereto. It is presented here as an example of a state of the art
drug, normally poorly soluble in its present delivery form, but
when properly delivered in a pharmaceutical microemulsion carrier,
the current problems can be solved. Such current problems in the
case of propofol stem directly from its poor solubility in water.
These include significant pain during injection, and post-operative
infections in some patients who, for example, receive a
macroemulsion of propofol for surgery or sedation.
[0010] In an attempt to lower health care costs, there has been an
explosive growth in the number of surgical procedures being done on
an outpatient basis in the United States. In the outpatient
setting, the use of short acting anesthetics allows for prompt
emergence from anesthesia and provides expeditious discharge of
patients to their home. Propofol (2,6-diisopropylphenol, molecular
weight 178.27) is an organic liquid similar to oil, has very little
solubility in the aqueous phase (octanol/water partition
coefficient 6761:1 at a pH 6.0-8.5), and is a short-acting
intravenous anesthetic that meets the criteria of rapid anesthetic
emergence with minimal side effects. Currently, propofol is
supplied as a macroemulsion, an opaque dispersion using
biocompatible emulsifiers such as phospholipids, cholesterol, and
others. In addition, a number of other drawbacks cause significant
limitations and risk to some patients.
[0011] Most of the disadvantages of propofol relate to its
commercial formulation and physical properties. That is, propofol
is a liquid at room temperature and is extremely insoluble in
water. The inherent lipophilicity of propofol makes dissolution in
saline or phosphate buffer problematic. In the early 1980's,
Cremaphor was used as a solvent, but subsequently abandoned because
of its propensity to cause life threatening anaphylactic reactions.
Since that time, propofol is suspended in a macroemulsion
consisting of 10% Intralipid, a milky white solution of soybean oil
and other additives as specified previously. The current commercial
formulation of propofol has several major disadvantages. First, use
of propofol in Intralipid has been implicated as the causative
agent contributing to several cases of postoperative infection in
human patients as detailed by the Center for Disease Control and
Prevention. The cause of the infections and death was attributed to
extrinsically contaminated Diprivan (i.e., propofol in Intralipid)
used as an anesthetic during the surgical procedures. To address
the propensity of bacterial growth, manufacturers added the
preservatives EDTA (0.05 mg/ml) to Diprivan and sodium
metabisulfite (0.25 mg/ml) to Baxter PPI propofol. Unfortunately,
both of these preservatives may potentially cause adverse reactions
in humans. Whereas sodium metabisulfite may cause allergic-type
reactions in susceptible patients, the chelating properties of EDTA
were of concern to the FDA because of their effects on cardiac
conduction and renal function. Thus, use of a solvent that does not
support bacterial growth would significantly enhance the
therapeutic safety of propofol not only by preventing intravenous
injection of microbes, but also by obviating the need for
preservatives and possible adverse effects of these agents.
[0012] Second, the cost of Intralipid substantially adds to the
expense of manufacturing a propofol macroemulsion. This vehicle is
produced by Clinitec, licensed to the pharmaceutical corporations
for the purpose of solubilizing propofol, and constitutes a major
fraction of the cost of producing Diprivan (propofol in 10%
Intralipid).
[0013] A third major disadvantage of the current preparation of
propofol relates to its free, aqueous concentrations. Propofol is a
phenol derivative (2,6-diisopropylphenol) and causes pain on
injection. This effect is the single greatest complaint of
anesthesiologists and patients regarding propofol and may on
occasion necessitate discontinuation of the drug for sedative
purposes. Most authorities believe that the stinging relates to the
concentration of propofol in free, aqueous solution.
[0014] A solvent that completely emulsifies or partitions propofol
into the non-aqueous phase would preclude (or markedly reduce)
stinging and allow painless injection similar to thiopental sodium
(another widely used intravenous anesthetic). The formulations of
the present invention address and overcome these three
disadvantages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 shows release of active drug from microemulsions or
micelles to Heptane phase.
[0016] FIG. 2 shows similar experimental results.
SUMMARY OF THE INVENTION
[0017] A microemulsion delivery system for normally water insoluble
or sparingly soluble drugs, such as propofol. The drug is
microemulsified with an emulsifier combination of a long chain
polymer surfactant component and a short chain fatty acid
surfactant component. These are selected to reduce surface tension
to absorption between the two phases to thereby allow the formation
of thermodynamically stable microemulsions or micelles. The system
is particularly useful for propofol, but is not limited to
propofol.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] Microemulsion drug delivery systems of this invention are
hereinafter described in conjunction with microemulsions with the
pharmaceutically active anesthetic propofol. However, it should be
understood that the use of propofol as the active water insoluble
or sparingly soluble drug in the description is exemplary only of
the generally described class of normally poorly water soluble
drugs. Microemulsion systems of the present invention, particularly
oil and water, can be used to dissolve substantial concentrations
of oil-soluble drugs such as propofol, and they can thereafter be
injected intravenously into human patients or animals with less, or
even without pain caused by the delivery system.
[0019] Many water soluble drugs such as cyclosporine, insulin, and
others can be dissolved in water-in-oil microemulsions and can be
taken orally (e.g., gelatin capsule) or injected. These
microemulsions spread over the intestinal surface wherein
nanometer-sized water droplets with drugs dissolved therein
permeate and diffuse across the intestinal brush border. The
delivery of various drugs (i.e., oil-soluble, water-soluble, and
interphase soluble drugs) in patients using the
previously-mentioned three types of microemulsion systems
consisting of biocompatible surfactants and co-surfactants will
work. Such solutions can be especially valuable to patients with
abdominal disorders that inhibit absorption such as short gut
syndrome and for better oral delivery of expensive drugs that are
otherwise poorly absorbed.
[0020] Substantially water insoluble pharmacologically active
agents contemplated for use in the practice of the present
invention include pharmaceutically active agents, not limited in
class, except to say they are normally difficultly soluble in
aqueous systems. Examples of pharmaceutically active drug agents
include:
[0021] analgesics/antipyretics (e.g., aspirin, acetaminophen,
ibuprofen, naproxen sodium, buprenorphine hydrochloride,
propoxyphene hydrochloride, propoxyphene napsylate, meperidine
hydrochloride, hydromorphone hydrochloride, morphine sulfate,
oxycodone hydrochloride, codeine phosphate, dihydrocodeine
bitartrate, pentazocine hydrochloride, hydrocodone bitartrate,
levorphanol tartrate, diflunisal, trolamine salicylate, nalbuphine
hydrochloride, mefenamic acid, butorphanol tartrate, choline
salicylate, butalbital, phenyltoloxamine citrate, diphenhydramine
citrate, methotrimeprazine, cinnamedrine hydrochloride,
meprobamate, and the like);
[0022] anesthetics (e.g., halothane, isoflurane, methoxyflurane,
propofol, thiobarbiturates, xenon and the like); antiasthmatics
(e.g., Azelastine, Ketotifen, Traxanox, and the like);
[0023] antibiotics (e.g., neomycin, streptomycin, chloramphenicol,
cephalosporin, ampicillin, penicillin, tetracycline, and the
like);
[0024] antidepressants (e.g., nefopam, oxypertine, doxepin
hydrochloride, amoxapine, trazodone hydrochloride, amitriptyline
hydrochloride, maprotiline hydrochloride, phenelzine sulfate,
desipramine hydrochloride, nortriptyline hydrochloride,
tranylcypromine sulfate, fluoxetine hydrochloride, doxepin
hydrochloride, imipramine hydrochloride, imipramine pamoate,
nortriptyline, amitriptyline hydrochloride, isocarboxazid,
desipramine hydrochloride, trimipramine maleate, protriptyline
hydrochloride, and the like);
[0025] antidiabetics (e.g., biguanides, hormones, sulfonylurea
derivatives, and the like);
[0026] antifungal agents (e.g., griseofulvin, keoconazole,
amphotericin B, Nystatin, candicidin, and the like);
[0027] antihypertensive agents (e.g., propanolol, propafenone,
oxyprenolol, nifedipine, reserpine, trimethaphan camsylate,
phenoxybenzamine hydrochloride, pargyline hydrochloride,
deserpidine, diazoxide, guanethidine monosulfate, minoxidil,
rescinamine, sodium nitroprusside, rauwolfia serpentina,
alseroxylon, phentolamine mesylate, reserpine, and the like);
[0028] anti-inflammatories (e.g., (non-steroidal) indomethacin,
naproxen, ibuprofen, ramifenazone, piroxicam, (steroidal)
cortisone, dexamethasone, fluazacort, hydrocortisone, prednisolone,
prednisone, and the like);
[0029] antineoplastics (e.g., adriamycin, cyclophosphamide,
actinomycin, bleomycin, duanorubicin, doxorubicin, epirubicin,
mitomycin, methotrexate, fluorouracil, carboplatin, carmustine
(BCNU), methyl-CCNU, cisplatin, etoposide, interferons,
camptothecin and derivatives thereof, phenesterine, taxol and
derivatives thereof, taxotere and derivatives thereof, vinblastine,
vincristine, tamoxifen, etoposide, piposulfan, and the like);
[0030] antianxiety agents (e.g., lorazepam, buspirone
hydrochloride, prazepam, chlordiazepoxide hydrochloride, oxazepam,
clorazepate dipotassium, diazepam, hydroxyzine pamoate, hydroxyzine
hydrochloride, alprazolam, droperidol, halazepam, chlormezanone,
dantrolene, and the like);
[0031] immunosuppressive agents (e.g., cyclosporine, azathioprine,
mizoribine, FK506 (tacrolimus), and the like); antimigraine agents
(e.g., ergotamine tartrate, propanolol hydrochloride, isometheptene
mucate, dichloralphenazone, and the like);
[0032] sedatives/hypnotics (e.g., barbiturates (e.g.,
pentobarbital, pentobarbital sodium, secobarbital sodium),
benzodiazapines (e.g., flurazepam hydrochloride, triazolam,
tomazeparm, midazolam hydrochloride, and the like);
[0033] antianginal agents (e.g., beta-adrenergic blockers, calcium
channel blockers (e.g., nifedipine, diltiazem hydrochloride, and
the like), nitrates (e.g., nitroglycerin, isosorbide dinitrate,
pentaerythritol tetranitrate, erythrityl tetranitrate, and the
like));
[0034] antipsychotic agents (e.g., haloperidol, loxapine succinate,
loxapine hydrochloride, thioridazine, thioridazine hydrochloride,
thiothixene, fluphenazine hydrochloride, fluphenazine decanoate,
fluphenazine enanthate, trifluoperazine hydrochloride,
chlorpromazine hydrochloride, perphenazine, lithium citrate,
prochlorperazine, and the like);
[0035] antimanic agents (e.g., lithium carbonate);
[0036] antiarrhythmics (e.g., amiodarone, related derivatives of
amiodarone, bretylium tosylate, esmolol hydrochloride, verapamil
hydrochloride, encainide hydrochloride, digoxin, digitoxin,
mexiletine hydrochloride, disopyramide phosphate, procainamide
hydrochloride, quinidine sulfate, quinidine gluconate, quinidine
polygalacturonate, flecainide acetate, tocainide hydrochloride,
lidocaine hydrochloride, and the like);
[0037] antiarthritic agents (e.g., phenylbutazone, sulindac,
penicillamine, salsalate, piroxicam, azathioprine, indomethacin,
meclofenamate sodium, gold sodium thiomalate, ketoprofen,
auranofin, aurothioglucose, tolmetin sodium, and the like);
[0038] antigout agents (e.g., colchicine, allopurinol, and the
like);
[0039] anticoagulants (e.g., heparin, heparin sodium, warfarin
sodium, and the like);
[0040] thrombolytic agents (e.g., urokinase, streptokinase,
altoplase, and the like);
[0041] antifibrinolytic agents (e.g., aminocaproic acid);
hemorheologic agents (e.g., pentoxifylline);
[0042] antiplatelet agents (e.g., aspirin, empirin, ascriptin, and
the like);
[0043] anticonvulsants (e.g., valproic acid, divalproate sodium,
phenytoin, phenytoin sodium, clonazepam, primidone, phenobarbitol,
phenobarbitol sodium, carbamazepine, amobarbital sodium,
methsuximide, metharbital, mephobarbital, mephenytoin,
phensuximide, paramethadione, ethotoin, phenacemide, secobarbitol
sodium, clorazepate dipotassium, trimethadione, and the like);
[0044] antiparkinson agents (e.g., ethosuximide, and the like);
antihistamines/antipruritics (e.g., hydroxyzine hydrochloride,
diphenhydramine hydrochloride, chlorpheniramine maleate,
brompheniramine maleate, cyproheptadine hydrochloride, terfenadine,
clemastine fumarate, triprolidine hydrochloride, carbinoxamine
maleate, diphenylpyraline hydrochloride, phenindamine tartrate,
azatadine maleate, tripelennamine hydrochloride,
dexchlorpheniramine maleate, methdilazine hydrochloride,
trimprazine tartrate and the like);
[0045] agents useful for calcium regulation (e.g., calcitonin,
parathyroid hormone, and the like);
[0046] antibacterial agents (e.g., amikacin sulfate, aztreonam,
chloramphenicol, chloramphenicol palmitate, chloramphenicol sodium
succinate, ciprofloxacin hydrochloride, clindamycin hydrochloride,
clindamycin palmitate, clindamycin phosphate, metronidazole,
metronidazole hydrochloride, gentamicin sulfate, lincomycin
hydrochloride, tobramycin sulfate, vancomycin hydrochloride,
polymyxin B sulfate, colistimethate sodium, colistin sulfate, and
the like);
[0047] antiviral agents (e.g., interferon gamma, zidovudine,
amantadine hydrochloride, ribavirin, acyclovir, and the like);
[0048] antimicrobials (e.g., cephalosporins (e.g., cefazolin
sodium, cephradine, cefaclor, cephapirin sodium, ceftizoxime
sodium, cefoperazone sodium, cefotetan disodium, cefutoxime azotil,
cefotaxime sodium, cefadroxil monohydrate, ceftazidime, cephalexin,
cephalothin sodium, cephalexin hydrochloride monohydrate,
cefamandole nafate, cefoxitin sodium, cefonicid sodium, ceforanide,
ceftriaxone sodium, ceftazidime, cefadroxil, cephradine, cefuroxime
sodium, and the like), prythronycins, penicillins (e.g.,
ampicillin, amoxicillin, penicillin G benzathine, cyclacillin,
ampicillin sodium, penicillin G potassium, penicillin V potassium,
piperacillin sodium, oxacillin sodium, bacampicillin hydrochloride,
cloxacillin sodium, ticarcillin disodium, azlocillin sodium,
carbenicillin indanyl sodium, penicillin G potassium, penicillin G
procaine, methicillin sodium, nafcillin sodium, and the like),
erythromycins (e.g., erythromycin ethylsuccinate, erythromycin,
erythromycin estolate, erythromycin lactobionate, erythromycin
siearate, erythromycin ethylsuccinate, and the like), tetracyclines
(e.g., tetracycline hydrochloride, doxycycline hyclate, minocycline
hydrochloride, and the like), and the like);
[0049] anti-infectives (e.g., GM-CSF);
[0050] bronchodilators (e.g., sympathomimetics (e.g., epinephrine
hydrochloride, metaproterenol sulfate, terbutaline sulfate,
isoetharine, isoetharine mesylate, isoetharine hydrochloride,
albuterol sulfate, albuterol, bitolterol, mesylate isoproterenol
hydrochloride, terbutaline sulfate, epinephrine bitartrate,
metaproterenol sulfate, epinephrine, epinephrine bitartrate),
anticholinergic agents (e.g., ipratropium bromide), xanthines
(e.g., aminophylline, dyphylline, metaproterenol sulfate,
aminophylline), mast cell stabilizers (e.g., cromolyn sodium),
inhalant corticosteroids (e.g., flurisolidebeclomethasone
dipropionate, beclomethasone dipropionate monohydrate), salbutamol,
beclomethasone dipropionate (BDP), ipratropium bromide, budesonide,
ketotifen, salmeterol, xinafoate, terbutaline sulfate,
triamcinolone, theophylline, nedocromil sodium, metaproterenol
sulfate, albuterol, flunisolide, and the like);
[0051] hormones (e.g., androgens (e.g., danazol, testosterone
cypionate, fluoxymesterone, ethyltostosterone, testosterone
enanihate, methyltestosterone, fluoxymesterone, testosterone
cypionate), estrogens (e.g., estradiol, estropipate, conjugated
estrogens), progestins (e.g., methoxyprogesterone acetate,
norethindrone acetate), corticosteroids (e.g., triamcinolone,
betamethasone, betamethasone sodium phosphate, dexamethasone,
dexamethasone sodium phosphate, dexamethasone acetate, prednisone,
methylprednisolone acetate suspension, triamcinolone acetonide,
methylprednisolone, prednisolone sodium phosphate
methylprednisolone sodium succinate, hydrocortisone sodium
succinate, methylprednisolone sodium succinate, triamcinolone
hexacatonide, hydrocortisone, hydrocortisone cypionate,
prednisolone, fluorocortisone acetate, paramethasone acetate,
prednisolone tebulate, prednisolone acetate, prednisolone sodium
phosphate, hydrocortisone sodium succinate, and the like), thyroid
hormones (e.g., levothyroxine sodium) and the like), and the
like;
[0052] hypoglycemic agents (e.g., human insulin, purified beef
insulin, purified pork insulin, glyburide, chlorpropamide,
glipizide, tolbutamide, tolazamide, and the like);
[0053] hypolipidemic agents (e.g., clofibrate, dextrothyroxine
sodium, probucol, lovastatin, niacin, and the like);
[0054] proteins (e.g., DNase, alginase, superoxide dismutase,
lipase, and the like);
[0055] nucleic acids (e.g., sense or anti-sense nucleic acids
encoding any therapeutically useful protein, including any of the
proteins described herein, and the like);
[0056] agents useful for erythropoiesis stimulation (e.g.,
erythropoietin);
[0057] antiulcer/antireflux agents (e.g., famotidine, cimetidine,
ranitidine hydrochloride, and the like);
[0058] antinauseants/antiemetics (e.g., meclizine hydrochloride,
nabilone, prochlorperazine, dimenhydrinate, promethazine
hydrochloride, thiethylperazine, scopolamine, and the like);
[0059] oil-soluble vitamins (e.g., vitamins A, D, E, K, and the
like);
[0060] as well as other drugs such as mitotane, visadine,
halonitrosoureas, anthrocyclines, ellipticine, and the like.
[0061] As well, the microemulsion systems of the present invention
may be used in brain chemotherapy and gene chemotherapy, since the
nature of the surface of virus particles is an important
determinant of the transfer rate of viruses across the blood/brain
barrier or into another protected compartment (e.g., intraocular
cerebrospinal fluid).
[0062] Likewise, many chemotherapeutic agents dissolved in an oil
in water microemulsion might be more readily delivered to a tumor
site in the brain. For example, pediatric patients with brain
tumors may frequently require general anesthesia so that
chemotherapeutic agents can be safely injected into the
cerebrospinal fluid by puncture of the lumbar cistern. Use of
microemulsions to target brain tumors might obviate the need for
anesthesia and/or lumbar puncture in adult and pediatric
patients.
[0063] The solubility of nonpolar drugs can be significantly
increased if dissolved in mixed solvents such as water and alcohol
or propylene glycol by influencing the hydrophobic forces existing
in the system. This approach will also be compared with
microemulsion and selective micelle release systems. The mixed
solvent system may be the simplest method to solve problems of drug
solubilization.
[0064] In preparation of the pharmaceutically active drug such as
propofol useful in highly bioavailable form in accordance with the
present invention, the first step is to select the normally
difficultly soluble drug, such as propofol, which is similar to an
oil. In order to make a homogeneous microemulsion of the
pharmaceutically active component such as propofol, one needs to
mix it with the appropriate emulsifier combination for formation of
the microemulsion.
[0065] Surprisingly, it has been found that in accordance with the
present invention, the appropriate combination of surfactants is
the combination of a long chain polymer surfactant component such
as a poloxamer with a short chain fatty acid surfactant component.
The ratio of long chain polymer surfactant to short chain fatty
acid surfactant should be from 10 to 100, preferably from 25 to 80
(wt./wt.).
[0066] Suitable long chain surfactants can be selected from the
group known as organic or inorganic surfactant pharmaceutical
excipients. Preferred surfactants include nonionic and anionic
surfactants.
[0067] Representative examples of long chain or high molecular
weight (>1000) surfactants include gelatin, casein, lecithin
(phosphatides), gum acacia, cholesterol, tragacanth,
polyoxyethylene alkyl ethers, e.g., macrogol ethers such as
cetomacrogol 1000, polyoxyethylene castor oil derivatives,
polyoxyethylene sorbitan fatty acid esters, e.g., the commercially
available Tweens, polyethylene glycols, polyoxyethylene stearates,
colloidal silicon dioxide, phosphates, sodium dodecylsulfate,
carboxymethylcellulose calcium, carboxymethylcellulose sodium,
methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose,
hydroxypropylmethylcellulose phthalate, microcrystalline cellulose,
magnesium aluminum silicate, triethanolamine, polyvinyl alcohol,
and polyvinylpyrrolidene (PVP). The low molecular weight (<1000)
include stearic acid, benzalkonium chloride, calcium stearate,
glycerol monostearate, cetostearyl alcohol, cetomacrogol
emulsifying wax, and sorbitan esters. Most of these surface
modifiers are known pharmaceutical excipients and are described in
detail in the Handbook of Pharmaceutical Excipients, published
jointly by the American Pharmaceutical Association and The
Pharmaceutical Society of Great Britain, the Pharmaceutical Press,
1986.
[0068] Particularly preferred long chain surfactants include
polyvinylpyrrolidone, tyloxapol, poloxamers such as Pluronic F68,
F77, and F108, which are block copolymers of ethylene oxide and
propylene oxide, and polyxamines such as Tetronic 908 (also known
as Poloxamine 908), which is a tetrafunctional block copolymer
derived from sequential addition of propylene oxide and ethylene
oxide to ethylenediamine, available from BASF, dextran, lecithin,
dialkylesters of sodium sulfosuccinic acid, such as Aerosol OT,
which is a dioctyl ester of sodium sulfosuccinic acid, available
from American Cyanamid, Duponol P, which is a sodium lauryl
sulfate, available from DuPont, Triton X-200, which is an alkyl
aryl polyether sulfonate, available from Rohm and Haas, Tween 20
and Tween 80, which are polyoxyethylene sorbitan fatty acid esters,
available from ICI Specialty Chemicals; Carbowax 3550 and 934,
which are polyethylene glycols available from Union Carbide;
Crodesta F-110, which is a mixture of sucrose stearate and sucrose
distearate, available from Croda Inc., Crodesta SL-40, which is
available from Croda, Inc., and SA90HCO, which is C.sub.18
H.sub.37-CH.sub.2(CON(CH.sub.3)CH.su- b.2 (CHOH).sub.4
CH.sub.2OH).sub.2. Surface modifiers which have been found to be
particularly useful include Tetronic 908, the Tweens, Pluronic F-68
and polyvinylpyrrolidone. Other useful surface modifiers include:
decanoyl-N-methylglucamide; n-decyl.beta-D-glucsopyranoside;
n-decyl.beta-D-maltopyranoside; n-dodecyl.beta-D-glucopyranoside;
n-dodecyl.beta.-D-maltoside; heptanoyl-N-methylglucamide;
n-heptyl-.beta.-D-glucopyranoside; n-heptyl.beta.-D-thioglucoside;
n-hexyl.beta.-D-glucopyranoside; nonanoyl-N-methylglucamide;
n-noyl.beta.-D-glucopyranoside; octanoyl-N-methylglucamide;
n-octyl-.beta.-D-glucopyranoside;
octyl.beta.-D-thioglucopyranoside; and the like.
[0069] Another useful long chain surfactant is tyloxapol (a
nonionic liquid polymer of the alkyl aryl polyether alcohol type;
also known as superinone or triton). This surfactant is
commercially available and/or can be prepared by techniques known
in the art.
[0070] Another preferred surfactant p-isononylphenoxypoly
(glycidol) also known as Olin-10G or Surfactant 10-G, is
commercially available as 10G from Olin Chemicals, Stamford,
Conn.
[0071] One preferred long chain surfactant is a block copolymer
linked to at least one anionic group. The polymers contain at least
one, and preferably two, three, four or more anionic groups per
molecule. Preferred anionic groups include sulfate, sulfonate,
phosphonate, phosphate and carboxylate groups. The anionic groups
are covalently attached to the nonionic block copolymer. The
nonionic sulfated polymeric surfactant has a molecular weight of
1,000-50,000, preferably 2,000-40,000, and more preferably
3,000-30,000. In preferred embodiments, the polymer comprises at
least about 50%, and more preferably, at least about 60% by weight
of hydrophilic units, e.g., alkylene oxide units. The reason for
this is that the presence of a major weight proportion of
hydrophilic units confers aqueous solubility to the polymer.
[0072] A preferred class of block copolymers useful as surface
modifiers herein includes block copolymers of ethylene oxide and
propylene oxide. These block copolymers are commercially available
as Pluronics. Specific examples of the block copolymers include
F68, F77, F108 and F127.
[0073] Another preferred class of block copolymers useful herein
include tetrafunctional block copolymers derived from sequential
addition of ethylene oxide and propylene oxide to ethylene diamine.
These polymers, in an unsulfated form, are commercially available
as Tetronics.
[0074] To summarize, the long chain surfactant is preferably a
block copolymer which is a poloxamer which is a copolymer of
ethylene oxide and propylene oxide. These copolymers are
commercially available as Pluronics.RTM..
[0075] The second component of the co-surfactant or emulsifier
combination is a short chain fatty acid component. By short chain
is meant C.sub.8 to C.sub.16 chain length, preferably, C.sub.8 to
C.sub.12. One preferred co-emulsifier with especially good results
is sodium laurate.
[0076] The advantages of this combination system are that one can
solubilize a broad range of concentrations of active drugs and
optimize the exact composition of the microemulsion components. For
example, with respect to propofol, high concentrations can be
achieved if desired by using higher concentrations of the
co-emulsifiers. Concentrations of propofol used by healthcare
providers (i.e., 1% concentrate, 10 mg/mL) can be very easily
achieved in the present system shown by Tables 1, 2, 3 and 4 with
respect to the examples below. These are all clear solutions,
colorless, thermodynamically stable over time (currently these have
been demonstrated for stability up to at least 16 months), and do
not support bacterial growth.
[0077] In addition to microemulsions, one can design the interface
of such nanometer-sized droplets so that droplet stability and
lifespan in humans can be selectively designed to last from a few
milliseconds to minutes, or even to hours. We believe that the
interfacial rigidity of the microemulsion droplets plays a key role
in the flux of the drugs from such droplets to the cells and
tissues. Tailoring of microemulsion systems to control the flux of
the drugs can also be manipulated in such systems to customize drug
delivery according to individual patient requirements or to
specific pharmaceutical needs.
[0078] A mixture of one or more of the drug active ingredients in
the microemulsion carrier composition of the present invention to
generally lower the interfacial tension of the active ingredient to
less than 0.1 duines/cm with a drop size of the active ingredient
in the carrier liquid being preferably less than 200 nm. Preferably
the combination that comprises the long chain polymer surfactant
component in a short chain fatty acid surfactant component are
selected so that they are safe to be taken by humans either orally
or intravenously. In providing the composition for administration
to humans intravenously and safely intravenously, the concentration
would normally be less than 1000 mg of active material per one mL
of total material. Of course, the surfactant and the cosurfactant
i.e. the long chain polymer surfactant active component and the
short chain fatty acid surface active component are preferably
selected from the GRAS list.
[0079] Drugs such as lidocaine and tetracaine can be obtained in
base form (nonionic or unionized) or salt (ionic) form. The salt
form of drugs has a much greater solubility in aqueous phase (i.e.,
water). For this reason, many drugs are commonly supplied in the
salt form in the aqueous phase. We have shown that surface active
drug molecules form micelles in the aqueous phase. These micelles
can easily solubilize nonpolar or nonionic forms of drugs. Thus, we
have shown that the solubility of a drug can be three to five-fold
greater in the aqueous phase if we put ionized and unionized forms
of lidocaine into the aqueous phase.
[0080] When injected into a peripheral vein (e.g., arm or hand
vein), the microemulsion would be designed in a manner that it may
or may not release the lipophilic drug that it is holding until it
enters the central blood circulation. Using this design approach,
patient safety and comfort would be markedly improved.
Specifically, the damage and/or pain associated with peripheral
intravenous injection for certain drugs such as chemotherapeutic
agents and propofol could be significantly reduced or even
eliminated. This technique may avoid the risks of placing a
catheter into the central circulation to administer these types of
drugs.
[0081] Further modification of this approach can also be made so
that one can tailor a micelle of a bio-compatible surfactant having
definite stability or lifetime (milliseconds to hours). Solubility
of these drugs and transfer to the surrounding medium is
significantly influenced by the lifetime and, hence stability of
the micelles. Experimental techniques are available to
scientifically measure the stability of micelles from
10.sup.-3-10.sup.3 seconds range. One can then correlate micellar
stability and drug release rate. Such studies can be performed
using the Franz diffusion cell wherein hairless mouse skin serves
as a diffusion barrier between the donor and receptor cell
compartments. In the donor compartment, micelles are placed with a
specific relaxation time (i.e., lifetime or stability). A given
drug's transfer rate into the receptor compartment can be measured
and correlated to the stability of the micelles and drug release
rate. Recently, we have performed similar studies using nonpolar
dye molecules that were solubilized in micelles into the aqueous
phase (FIG. 1).
[0082] Micelle stability significantly affects transfer rate of
drugs. For example, one might deliver a long-acting, peripheral
neural blockade using lidocaine instead of bupivicaine by encasing
lidocaine in micelles with life spans of several hours. Because the
therapeutic index for cardiotoxic effects of lidocaine is much
greater than that for bupivicaine, use of tailored micelles would
significantly enhance patient safety. (Therapeutic index is a
pharmacological term regarding the margin of safety to be expected
for a certain concentration of a drug to produce a desired effect
[e.g., TD.sub.50] compared to the concentration that causes an
undesired effect [e.g., LD.sub.50]). Similarly, long-lived micelles
might be useful for coating drug particles or viruses for
permeation through the blood/brain barrier.
[0083] The following examples are further offered to illustrate but
not limit the invention. In the examples herein, propofol was used
as the drug selected. Propofol was used with a microemulsion
emulsifier combination of Pluronic.RTM. F77 and sodium laurate in
amounts specified below. Microemulsions with the emulsifier
combination saline and propofol were made. Stability and viscosity
were determined, using conventional methods and tabulated in Tables
1, 2, 3 and 4 below.
1TABLE 1 Formulation parameters of propofol microemulsions Total
volume = 100 ml Sample Pluronic Sodium Propofol Number F-77(gm)
laurate(gm) (ml) 1A 4.0 -- -- 2A 4.0 -- 1.0 3A 4.0 0.05 1.0 4A 4.0
0.10 1.0 5A 4.0 0.15 1.0 1B 4.5 -- -- 2B 4.5 -- 1.0 3B 4.5 0.05 1.0
4B 4.5 0.10 1.0 5B 4.5 0.15 1.0
[0084]
2TABLE 2 The effect of temperature, and sodium laurate
concentration and storage time on droplet size of propofol
microemulsions. Particle Size(nm) Particle Size(nm) Particle
Size(nm) Freshly prepared(A) 2 weeks later(B) 5 months later(C) Age
25.degree. C. 37.degree. C. 25.degree. C. 37.degree. C. 25.degree.
C. 37.degree. C. 1A -- -- -- -- -- -- 2A 93.4 35.5 96.4 36.2 104.3
39.1 3A 29.8 28.1 30.9 28.7 33.5 30.1 4A 29.3 26.9 30.4 28.2 31.5
29.0 5A 25.1 24.2 25.7 25.1 25.3 25.1 1B -- -- -- -- -- -- 2B 72.1
32.8 78.7 35.8 85.6 38.3 3B 29.3 27.4 29.7 27.7 30.5 28.3 4B 26.9
25.1 27.4 25.6 27.4 25.8 5B 24.6 24.1 24.7 24.3 24.9 24.7
[0085]
3TABLE 3 The effect of temperature, and sodium laurate
concentration and storage time on pH level of propofol
microemulsions pH pH pH Freshly 2 weeks 5 months prepared(A)
later(B) later(C) Age 25.degree. C. 37.degree. C. 25.degree. C.
37.degree. C. 25.degree. C. 37.degree. C. Pf 77-1 6.58 6.58 6.55
6.52 6.5 6.5 Pf 77-2 6.42 6.43 6.37 6.34 6.34 6.36 Pf 77-3 7.32 7.3
7.11 7.08 7.14 7.06 Pf 77-4 7.53 4.5 7.42 7.24 7.38 7.24 Pf 77-5
7.62 7.66 7.58 7.4 7.52 7.42 Pf 77-1 6.59 6.58 6.5 6.48 6.5 6.52 Pf
77-2 6.42 6.41 6.34 6.30 6.36 6.3 Pf 77-3 7.44 7.38 7.24 7.32 7.28
7.34 Pf 77-4 7.57 7.54 7.46 7.5 7.5 7.52 Pf 77-5 7.6 7.62 7.56 7.58
7.55 7.55
[0086]
4TABLE 4-A The effect of temperature and shear rate on viscosity of
freshly prepared propofol microemulsions Viscosity Viscosity
Viscosity Viscosity Viscosity Viscosity in cps in cps in cps in cps
in cps in cps Code of 10 S.sup.-1 10 S.sup.-1 100 S.sup.-1 100
S.sup.-1 1000 S.sup.-1 1000 S.sup.-1 Emulsion 25.degree. C.
37.degree. C. 25.degree. C. 37.degree. C. 25.degree. C. 37.degree.
C. 1A 1.77 1.57 1.73 1.27 1.73 1.26 2A 53.45 33.45 13.20 1.26 5.14
4.66 3A 2.22 1.49 1.94 1.255 1.77 1.21 4A 2.18 1.33 1.81 1.20 1.71
1.20 5A 1.66 1.34 1.64 1.24 1.635 1.205 1B 1.75 1.59 1.81 1.35 1.80
1.36 2B 13.2 1.44 6.37 1.31 3.46 1.28 3B 2 .04 1.51 1.87 1.33 1.79
1.30 4B 1.85 1.41 1.80 1.30 1.77 1.29 5B 1.43 1.21 1.58 1.22 1.47
1.206
[0087]
5TABLE 4-B The effect of temperature and shear rate on viscosity of
two week old propofol microemulsions Viscosity Viscosity Viscosity
Viscosity Viscosity Viscosity in cps in cps in cps in cps in cps in
cps Code of 10 S.sup.-1 10 S.sup.-1 100 S.sup.-1 100 S.sup.-1 1000
S.sup.-1 1000 S.sup.-1 Emulsion 25.degree. C. 37.degree. C.
25.degree. C. 37.degree. C. 25.degree. C. 37.degree. C. 1A 1.77
1.57 1.73 1.275 1.73 1.29 2A 59.5 20.95 14.3 10.4 5.52 4.39 3A 3.13
1.66 2.37 1.24 1.97 1.20 4A 2.51 1.34 1.91 1.21 1.75 1.22 5A 1.69
1.51 1.62 1.23 1.63 1.23 1B 1.74 1.63 1.80 1.35 1.81 1.35 2B 13.0
1.49 6.36 1.40 3.47 1.35 3B 2.06 1.69 1.91 1.33 1.91 1.32 4B 1.86
1.51 1.81 1.29 1.79 1.27 5B -- -- -- -- -- --
[0088]
6TABLE 4-C The effect of temperature and shear rate on viscosity of
five month old propofol microemulsions Viscosity Viscosity
Viscosity Viscosity Viscosity Viscosity in cps in cps in cps in cps
in cps in cps Code of 10 S.sup.-1 10 S.sup.-1 100 S.sup.-1 100
S.sup.-1 1000 S.sup.-1 1000 S.sup.-1 Emulsion 25.degree. C.
37.degree. C. 25.degree. C. 37.degree. C. 25.degree. C. 37.degree.
C. 1A 1.78 1.590 1.70 1.278 1.72 1.280 2A 60.04 21.55 14.6 10.70
5.70 4.52 3A 3.30 1.77 2.46 1.324 2.13 1.28 4A 2.58 1.388 1.97 1.25
1.79 1.25 5A 1.66 1.534 1.59 1.249 1.60 1.245 1B 1.73 1.55 1.86
1.308 1.82 1.374 2B 13.9 1.514 6.64 1.512 3.64 1.450 3B 2.04 1.71
1.96 1.365 1.87 1.350 4B 1.90 1.55 1.86 1.308 1.84 1.280 5B -- --
-- -- -- --
[0089] Release from microemulsion micelles of the dye orange OT,
using the co-emulsion combination of pluronic 77 and sodium
laurate, are illustrated at 4, 6 and 10 hours respectively in FIGS.
1 and 2. As can be seen, the release rate is influenced by the
micelles.
[0090] The anesthetic properties of propofol as a microemulsion in
0.9% normal saline (NS) with a Pluronic acid emulsifier were
compared to those of propofol as a macroemulsion in Intralipid
(Diprivan.RTM.) using a randomized, crossover design in a rat model
for intravenous anesthetic induction and recovery.
[0091] This protocol was approved by the Animal Care and Use
Committee of the University of Florida. Intravenous catheters (24
g) were inserted and secured in tail veins of Harlan Sprague-Dawley
rats (350 g). Catheters were maintained with a cap and flushed with
heparinized saline. Subsequently, rats were randomly administered
either propofol/NS/Pluronic F-77 (University of Florida) after
filtration through a 0.20 .mu.m filter or sterile
propofol/Intralipid (Diprivan.RTM., AstraZeneca Pharmaceuticals,
Inc., Wilmington, Del.) at a rate of 10 mg/kg/min. To remove the
variability associated with the rate of injection caused by manual
bolus administration and its effect on the rate of anesthetic
induction, a syringe pump (sp2000i, World Precision Instruments,
Sarasota, Fla.) was used to assure a constant rate of drug
administration. Body temperature was maintained using a heating
blanket (TP-400, Gaymar Industries, Inc., Orchard Park, N.Y.). The
endpoint of anesthetic induction was total drug dose to cause the
loss of reflexive withdrawal of the leg following a left great toe
pinch. Following loss of withdrawal, the drug infusion was
discontinued. Endpoints of anesthetic recovery were timed until
recovery of spontaneous eye blinking, sustained head lift, and
righting reflex. Following the first anesthetic and recovery, rats
were allowed to fully recover for approximately 45 min. before
receiving the alternative formulation of propofol. Rats were
observed for seven days after receiving anesthesia.
[0092] All rats in both study groups experienced rapid induction of
anesthesia with subsequent recovery. Continuous spontaneous
ventilation occurred in every case. All rats maintained pink paws
and ears. No rat died during seven days of observation after the
anesthetic. Specific endpoints are detailed in Table 5.
7TABLE 5 Anesthetic induction and recovery properties of either
propofol in a microemulsion using NS/Pluronic F-77 or propofol in a
macroemulsion of Intralipid (Diprivan .RTM.) in rats.
Propofol/NS/Pluronic Propofol/Intralipid Parameter F-77
Microemulsion Macroemulsion P value.sup.a Total propofol 17.5 .+-.
2.2 14.9 .+-. 1.4 0.354 dose (mg/kg) Time to eye 609 .+-. 86 802
.+-. 57 0.184 blinking (sec) Time to head lift 691 .+-. 98 827 .+-.
63 0.459 (sec) Time to righting 756 .+-. 97 895 .+-. 34 0.393 (sec)
Data expressed as mean .+-. SEM of three experiments.
.sup.a2-tailed, paired t-test.
[0093] Based on these limited observations in a rat model, the
anesthetic properties of propofol in a NS/Pluronic F-77
microemulsion formulation are at least equivalent to those of the
commercially available propofol preparation, Diprivan.RTM..
[0094] From the above it can be seen that the invention
accomplishes at least all of its stated objectives. And, an
important aspect of which is the combination emulsifier system of a
long chain polymer surfactant component, and a short chain fatty
acid component which set up a competitive adsorption at the
interface of the oil and water to reduce interfacial tension to a
very low value. This allows the formation of stable microemulsions,
particularly so with the preferred drug propofol and the preferred
emulsifier combination pluronic F77 and sodium laurate. The formed
microemulsion is clear, not milky appearing at all times.
[0095] It, of course, goes without saying that certain
modifications of the emulsification system can be made without
departing from the spirit and scope of the present invention.
* * * * *