Title:  Compositions and methods for improved delivery of hydrophobic agents

United States Patent:  6,451,339

Issued:  September 17, 2002

Inventors:  Patel; Mahesh V. (Salt Lake City, UT); Chen; Feng-Jing (Salt Lake City, UT)

Assignee:  Lipocine, Inc. (Salt Lake City, UT)

Appl. No.:  898553

Filed:  July 2, 2001

The present invention relates to triglyceride-free pharmaceutical compositions for delivery of hydrophobic therapeutic agents. Compositions of the present invention include a hydrophobic therapeutic agent and a carrier, where the carrier is formed from a combination of a hydrophilic surfactant and a hydrophobic surfactant. Upon dilution with an aqueous solvent, the composition forms a clear, aqueous dispersion of the surfactants containing the therapeutic agent. The invention also provides methods of treatment with hydrophobic therapeutic agents using these compositions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention overcomes the problems described above characteristic of conventional formulations such as micelle formulations, emulsions, and microemulsions, by providing unique triglyceride-free pharmaceutical compositions. Surprisingly, the present inventors have found that compositions including a combination of a hydrophilic surfactant and a hydrophobic surfactant can solubilize therapeutically effective amounts of hydrophobic therapeutic agents without recourse to the use of triglycerides, thereby avoiding the lipolysis dependence and other disadvantages of conventional formulations. Use of these formulations results in an enhanced rate and/or extent of absorption of the hydrophobic therapeutic agent.

A. Pharmaceutical Compositions

In one embodiment, the present invention provides a pharmaceutical composition including a carrier and a hydrophobic therapeutic agent. The carrier includes a hydrophilic surfactant and a hydrophobic surfactant in amounts such that upon dilution with an aqueous solution the carrier forms a clear aqueous dispersion of the hydrophilic and hydrophobic surfactants containing the hydrophobic therapeutic agent. It is a particular feature of the present invention that the carrier is substantially free of triglycerides, thereby providing surprising and important advantages over conventional, triglyceride-containing formulations.

1. Surfactants

The carrier includes at least one hydrophilic surfactant and at least one hydrophobic surfactant. As is well known in the art, the terms "hydrophilic" and "hydrophobic" are relative terms. To function as a surfactant, a compound must necessarily include polar or charged hydrophilic moieties as well as non-polar hydrophobic (lipophilic) moieties; i.e., a surfactant compound must be amphiphilic. An empirical parameter commonly used to characterize the relative hydrophilicity and hydrophobicity of non-ionic amphiphilic compounds is the hydrophilic-lipophilic balance ("HLB" value). Surfactants with lower HLB values are more hydrophobic, and have greater solubility in oils, while surfactants with higher HLB values are more hydrophilic, and have greater solubility in aqueous solutions.

Using HLB values as a rough guide, hydrophilic surfactants are generally considered to be those compounds having an HLB value greater than about 10, as well as anionic, cationic, or zwitterionic compounds for which the HLB scale is not generally applicable. Similarly, hydrophobic surfactants are compounds having an HLB value less than about 10.

It should be appreciated that the HLB value of a surfactant is merely a rough guide generally used to enable formulation of industrial, pharmaceutical and cosmetic emulsions. For many important surfactants, including several polyethoxylated surfactants, it has been reported that HLB values can differ by as much as about 8 HLB units, depending upon the empirical method chosen to determine the HLB value (Schott, J. Pharm. Sciences, 79(1), 87-88 (1990)). Likewise, for certain polypropylene oxide containing block copolymers (PLURONIC.RTM. surfactants, BASF Corp.), the HLB values may not accurately reflect the true physical chemical nature of the compounds. Finally, commercial surfactant products are generally not pure compounds, but are complex mixtures of compounds, and the HLB value reported for a particular compound may more accurately be characteristic of the commercial product of which the compound is a major component. Different commercial products having the same primary surfactant component can, and typically do, have different HLB values. In addition, a certain amount of lot-to-lot variability is expected even for a single commercial surfactant product. Keeping these inherent difficulties in mind, and using HLB values as a guide, one skilled in the art can readily identify surfactants having suitable hydrophilicity or hydrophobicity for use in the present invention, as described herein.

The hydrophilic surfactant can be any hydrophilic surfactant suitable for use in pharmaceutical compositions. Such surfactants can be anionic, cationic, zwitterionic or non-ionic, although non-ionic hydrophilic surfactants are presently preferred. As discussed above, these non-ionic hydrophilic surfactants will generally have HLB values greater than about 10. Mixtures of hydrophilic surfactants are also within the scope of the invention.

Similarly, the hydrophobic surfactant can be any hydrophobic surfactant suitable for use in pharmaceutical compositions. In general, suitable hydrophobic surfactants will have an HLB value less than about 10. Mixtures of hydrophobic surfactants are also within the scope of the invention.

The choice of specific hydrophobic and hydrophilic surfactants should be made keeping in mind the particular hydrophobic therapeutic agent to be used in the composition, and the range of polarity appropriate for the chosen therapeutic agent, as discussed in more detail below. With these general principles in mind, a very broad range of surfactants is suitable for use in the present invention. 

1.1. Polyethoxylated Fatty Acids

Although polyethylene glycol (PEG) itself does not function as a surfactant, a variety of PEG-fatty acid esters have useful surfactant properties. Among the PEG-fatty acid monoesters, esters of lauric acid, oleic acid, and stearic acid are most useful.  The preferred hydrophilic surfactants include PEG-8 laurate, PEG-8 oleate, PEG-8 stearate, PEG-9 oleate, PEG-10 laurate, PEG-10 oleate, PEG-12 laurate, PEG-12 oleate, PEG-15 oleate, PEG-20 laurate and PEG-20 oleate.

1.2 PEG-Fatty Acid Diesters

Polyethylene glycol fatty acid diesters are also suitable for use as surfactants in the compositions of the present invention.  The preferred hydrophilic surfactants include PEG-20 dilaurate, PEG-20 dioleate, PEG-20 distearate, PEG-32 dilaurate and PEG-32 dioleate.

1.3 PEG-Fatty Acid Mono- and Di-ester Mixtures

In general, mixtures of surfactants are also useful in the present invention, including mixtures of two or more commercial surfactant products. Several PEG-fatty acid esters are marketed commercially as mixtures or mono- and diesters.

1.4 Polyethylene Glycol Glycerol Fatty Acid Esters

The preferred hydrophilic surfactants are PEG-20 glyceryl laurate, PEG-30 glyceryl laurate, PEG-40 glyceryl laurate, PEG-20 glyceryl oleate, and PEG-30 glyceryl oleate.

1.5. Alcohol-Oil Transesterification Products

A large number of surfactants of different degrees of hydrophobicity or hydrophilicity can be prepared by reaction of alcohols or polyalcohols with a variety of natural and/or hydrogenated oils. Most commonly, the oils used are castor oil or hydrogenated castor oil, or an edible vegetable oil such as corn oil, olive oil, peanut oil, palm kernel oil, apricot kernel oil, or almond oil. Preferred alcohols include glycerol, propylene glycol, ethylene glycol, polyethylene glycol, sorbitol, and pentaerythritol. Among these alcohol-oil transesterified surfactants, preferred hydrophilic surfactants are PEG-35 castor oil (Incrocas-35), PEG-40 hydrogenated castor oil (Cremophor RH 40), PEG-25 trioleate (TAGAT.RTM. TO), PEG-60 corn glycerides (Crovol M70), PEG-60 almond oil (Crovol A70), PEG-40 palm kernel oil (Crovol PK70), PEG-50 castor oil (Emalex C-50), PEG-50 hydrogenated castor oil (Emalex HC-50), PEG-8 caprylic/capric glycerides (Labrasol), and PEG-6 caprylic/capric glycerides (Softigen 767). Preferred hydrophobic surfactants in this class include PEG-5 hydrogenated castor oil, PEG-7 hydrogenated castor oil, PEG-9 hydrogenated castor oil, PEG-6 corn oil (Labrafil.RTM. M 2125 CS), PEG-6 almond oil (Labrafil.RTM. M 1966 CS), PEG-6 apricot kernel oil (Labrafil.RTM. M 1944 CS), PEG-6 olive oil (Labrafil.RTM. M 1980 CS), PEG-6 peanut oil (Labrafil.RTM. M 1969 CS), PEG-6 hydrogenated palm kernel oil (Labrafil.RTM. M 2130 BS), PEG-6 palm kernel oil (Labrafil.RTM. M 2130 CS), PEG-6 triolein (Labrafil.RTM.b M 2735 CS), PEG-8 corn oil (Labrafil.RTM. WL 2609 BS), PEG-20 corn glycerides (Crovol M40), and PEG-20 almond glycerides (Crovol A40). The latter two surfactants are reported to have HLB values of 10, which is generally considered to be the approximate border line between hydrophilic and hydrophobic surfactants. For purposes of the present invention, these two surfactants are considered to be hydrophobic.

Also included as oils in this categoty of durfactants are oil-soluble vitamins, such as vitamins A, D, E, K, ect. Thus, derivatives of these vitamins, such as tocopheryl PEG-100 succinate (TPGS, available from Eastman), are also suitable surfactants.

1.6. Polyglycerized Fatty Acids

Polyglycerol esters of fatty acids are also suitable surfactants for the present invention. Among the polyglyceryl fatty acid esters, preferred hydrophobic surfactants include polyglyceryl oleate (Plurol Oleique), polyglyceryl-2 dioleate (Nikkol DGDO), and polyglyceryl-10 trioleate. Preferred hydrophilic surfactants include polyglyceryl-10 laurate (Nikkol Decaglyn 1-L), polyglyceryl-10 oleate (Nikkol Decaglyn 1-O), and polyglyceryl-10 mono, dioleate (Caprol.RTM. PEG 860). Polyglyceryl polyricinoleates (Polymuls) are also preferred hydrophilic and hydrophobic surfactants.

1.7. Propylene Glycol Fatty Acid Esters

Esters of propylene glycol and fatty acids are suitable surfactants for use in the present invention. In this surfactant class, preferred hydrophobic surfactants include propylene glycol monolaurate (Lauroglycol FCC), propylene glycol ricinoleate (Propymuls), propylene glycol monooleate (Myverol P-O6), propylene glycol dicaprylate/dicaprate (Captex.RTM. 200), and propylene glycol dioctanoate (Captex.RTM. 800).

1.8. Mixtures of Propylene Glycol Esters-Glycerol Esters

In general, mixtures of surfactants are also suitable for use in the present invention. In particular, mixtures of propylene glycol fatty acid esters and glycerol fatty acid esters are suitable and are commercially available. One preferred mixture is composed of the oleic acid esters of propylene glycol and glycerol (Arlacel 186).

1.9. Mono- and Diglycerides

A particularly important class of surfactants is the class of mono- and diglycerides. These surfactants are generally hydrophobic. Preferred hydrophobic surfactants in this class of compounds include glyceryl monooleate (Peceol), glyceryl ricinoleate, glyceryl laurate, glyceryl dilaurate (Capmul.RTM. GDL), glyceryl dioleate (Capmul.RTM. GDO), glyceryl mono/dioleate (Capmul.RTM. GMO-K), glyceryl caprylate/caprate (Capmul.RTM. MCM), caprylic acid mono/diglycerides (Imwitor.RTM. 988), and mono- and diacetylated monoglycerides (Myvacet.RTM. 9-45).

1.10. Sterol and Sterol Derivatives

Sterols and derivatives of sterols are suitable surfactants for use in the present invention. These surfactants can be hydrophilic or hydrophobic. Preferred derivatives include the polyethylene glycol derivatives. A preferred hydrophobic surfactant in this class is cholesterol. A preferred hydrophilic surfactant in this class is PEG-24 cholesterol ether (Solulan C-24).

1.11. Polyethylene Glycol Sorbitan Fatty Acid Esters

A variety of PEG-sorbitan fatty acid esters are available and are suitable for use as surfactants in the present invention. In general, these surfactants are hydrophilic, although several hydrophobic surfactants of this class can be used. Among the PEG-sorbitan fatty acid esters, preferred hydrophilic surfactants include PEG-20 sorbitan monolaurate (Tween-20), PEG-20 sorbitan monopalmitate (Tween-40), PEG-20 sorbitan monostearate (Tween-60), and PEG-20 sorbitan monooleate (Tween-80).

1.12. Polyethylene Glycol Alkyl Ethers

Ethers of polyethylene glycol and alkyl alcohols are suitable surfactants for use in the present invention. Preferred hydrophobic ethers include PEG-3 oleyl ether (Volpo 3) and PEG-4 lauryl ether (Brij 30).

1.13. Sugar Esters

Esters of sugars are suitable surfactants for use in the present invention. Preferred hydrophilic surfactants in this class include sucrose monopalmitate and sucrose monolaurate.
1.14. Polyethylene Glycol Alkyl Phenols

Several hydrophilic PEG-alkyl phenol surfactants are available, and are suitable for use in the present invention.

1.15. Polyoxyethylene-Polyoxypropylene Block Copolymers

The POE-POP block copolymers are a unique class of polymeric surfactants. The unique structure of the surfactants, with hydrophilic POE and hydrophobic POP moieties in well-defined ratios and positions, provides a wide variety of surfactants suitable for use in the present invention. These surfactants are available under various trade names, including Synperonic PE series (ICI); Pluronic.RTM. series (BASF), Emkalyx, Lutrol (BASF), Supronic, Monolan, Pluracare, and Plurodac. The generic term for these polymers is "poloxamer" (CAS 9003-11-6). These polymers have the formula:

HO(C₂ H₄ O)_a (C₃ H₆ O)_b (C₂ H₄ O)_a H

where "a" and "b" denote the number of polyoxyethylene and polyoxypropylene units, respectively.

Preferred hydrophilic surfactants of this class include Poloxamers 108, 188, 217, 238, 288, 338, and 407. Preferred hydrophobic surfactants in this class include Poloxamers 124, 182, 183, 212, 331, and 335.


1.16. Sorbitan Fatty Acid Esters

Sorbitan esters of fatty acids are suitable surfactants for use in the present invention. Among these esters, preferred hydrophobic surfactants include sorbitan monolaurate (Arlacel 20), sorbitan monopalmitate (Span-40), sorbitan monooleate (Span-80), sorbitan monostearate, and sorbitan tristearate.

1.17. Lower Alcohol Fatty Acid Esters

Esters of lower alcohols (C₂ to C₄) and fatty acids (C₈ to C₁₈) are suitable surfactants for use in the present invention. Among these esters, preferred hydrophobic surfactants include ethyl oleate (Crodamol EO), isopropyl myristate (Crodamol IPM), and isopropyl palmitate (Crodamol IPP).

1.18. Ionic Surfactants

Ionic surfactants, including cationic, anionic and zwitterionic surfactants, are suitable hydrophilic surfactants for use in the present invention. Preferred anionic surfactants include fatty acid salts and bile salts. Specifically, preferred ionic surfactants include sodium oleate, sodium lauryl sulfate, sodium lauryl sarcosinate, sodium dioctyl sulfosuccinate, sodium cholate, and sodium taurocholate.  It will be appreciated by one skilled in the art, however, that any bioacceptable counterion may be used. For example, although the fatty acids are shown as sodium salts, other cation counterions can also be used, such as alkali metal cations or ammonium. Unlike typical non-ionic surfactants, these ionic surfactants are generally available as pure compounds, rather than commercial (proprietary) mixtures. Because these compounds are readily available from a variety of commercial suppliers, such as Aldrich, Sigma, and the like.


1.19 Surfactant Concentrations

The hydrophilic and hydrophobic surfactants are present in the pharmaceutical compositions of the present invention in amounts such that upon dilution with an aqueous solution, the carrier forms a clear, aqueous dispersion of the hydrophilic and hydrophobic surfactants, containing the hydrophobic therapeutic agent. The relative amounts of hydrophilic and hydrophobic surfactants are readily determined by observing the properties of the resultant dispersion; i.e., when the relative amounts of the hydrophobic and hydrophilic surfactants are within a suitable range, the resultant aqueous dispersion is optically clear. When the relative amount of hydrophobic surfactant is too great, the resulting dispersion is visibly "cloudy", resembling a conventional emulsion or multiple phase system. Although a visibly cloudy solution may be potentially useful for some applications, such a system would suffer from many of the same disadvantages as conventional prior art formulations, as described above.

A convenient method of determining the appropriate relative concentrations for any hydrophilic surfactant-hydrophobic surfactant pair is as follows. A convenient working amount of a hydrophilic surfactant is provided, and a known amount of a hydrophobic surfactant is added. The surfactants are stirred to form a homogeneous mixture, with the aid of gentle heating if desired. The resulting mixture is diluted with purified water to prepare an aqueous dispersion. Any dilution amount can be chosen, but convenient dilutions are those within the range expected in vivo, about a 10 to 250-fold dilution. The aqueous dispersion is then assessed qualitatively for optical clarity. The procedure can be repeated with incremental variations in the relative amount of hydrophobic surfactant added, to determine the maximum relative amount of hydrophobic surfactant that can be present for a given surfactant pair.

Alternatively, the optical clarity of the aqueous dispersion can be measured using standard quantitative techniques for turbidity assessment. One convenient procedure to measure turbidity is to measure the amount of light of a given wavelength transmitted by the solution, using, for example, a UV-visible spectrophotometer. Using this measure, optical clarity corresponds to high transmittance, since cloudier solutions will scatter more of the incident radiation, resulting in lower transmittance measurements. If this procedure is used, care should be taken to insure that the surfactant mixture does not itself absorb light of the chosen wavelength, as any true absorbance necessarily reduces the amount of transmitted light and falsely increases the quantitative turbidity value. In the absence of chromophores at the chosen wavelength, suitable dispersions at a dilution of 10.times. should have an apparent absorbance of less than about 0.3, preferably less than about 0.2, and more preferably less than about 0.1. At a dilution of 100.times., suitable dispersions should have an apparent absorbance of less than about 0.1, preferably less than about 0.05, and more preferably less 17 than about 0.01.

A third method of determining optical clarity and carrier diffusivity through the aqueous boundary layer is to quantitatively measure the size of the particles of which the dispersion is composed. These measurements can be performed on commercially available particle size analyzers, such as, for example, a Nicomp particle size analyzer available from Particle Size Systems, Inc., of Santa Barbara, Calif. Using this measure, clear aqueous dispersions according to the present invention have average particle sizes much smaller than the wavelength of visible light, whereas dispersions containing excessive relative amounts of the hydrophobic surfactant have more complex particle size distributions, with much greater average particle sizes. It is desirable that the average particle size be less than about 100 nm, preferably less than about 50 nm, more preferably less than about 30 nm, and still more preferably less than about 20 nm. It is also preferred that the particle size distribution be mono-modal. As is shown in more detail in the Examples herein, dispersions having an undesirably large relative amount of hydrophobic surfactant typically display bimodal particle size distributions, such distributions having a small particle size component, typically less than about 30 nm, and a large particle size component, typically on the order of 100 nm or more. It should be emphasized that these particle sizes are appropriate for the carrier particles in aqueous solution, in the absence of a hydrophobic therapeutic agent. It is expected that the presence of the hydrophobic therapeutic agent may result in an increase in the average particle size.

Other methods of determining optical clarity or particle size can be used as desired. Such methods are well know to those skilled in the art.

It should be emphasized that any or all of the available methods may be used to ensure that the resulting aqueous dispersions possess the requisite optical clarity. For convenience, however, the present inventors prefer to use the simple qualitative procedure; i.e., simple visible observation. However, in order to more fully illustrate the practice of the present invention, all three of the above measures are used to assess the dispersion clarity in the Examples herein.

Although it should be understood that any aqueous dispersion having the properties described above is within the scope of the present invention regardless of the specific relative amounts of hydrophobic and hydrophilic surfactants, it is expected that the amount of hydrophobic surfactant will generally be less than about 200% by weight, based on the amount of hydrophilic surfactant, and more specifically, in the range of about 1% to 200%. Further, based on observations reported in the Examples herein, it is expected that the amount of hydrophobic surfactant will generally be less than about 100%, and more specifically in the range of about 5% to about 100% by weight, or about 10% to about 100% by weight, based on the amount of hydrophilic surfactant. For some particular surfactant combinations, cloudy solutions result when the amount of hydrophobic surfactant is greater than about 60% by weight, based on the amount of hydrophilic surfactant. A preferred range for these surfactants is about 1% to about 60%, preferably about 5% to about 60%, and more preferably about 10% to about 60%. Addition of optional excipients as described below can further increase the maximum relative amount of hydrophobic surfactant that can be used.

Other considerations well known to those skilled in the art will further inform the choice of specific proportions of hydrophobic and hydrophilic surfactants. These considerations include the degree of bioacceptability of the surfactants, and the desired dosage of hydrophobic therapeutic agent to be provided. In some cases, the amount of hydrophobic surfactant actually used in a pharmaceutical composition according to the present invention will be less than the maximum that can be used, and it should be apparent that such compositions are also within the scope of the present invention.

2. Hydrophobic Therapeutic Agents

Hydrophobic therapeutic agents suitable for use in the pharmaceutical compositions of the present invention are not particularly limited, as the carrier is surprisingly capable of solubilizing and delivering a wide variety of hydrophobic therapeutic agents. Hydrophobic therapeutic agents are compounds with little or no water solubility. Intrinsic water solubilities (i.e., water solubility of the unionized form) for hydrophobic therapeutic agents usable in the present invention are less than about 1% by weight, and typically less than about 0.1% or 0.01% by weight. Such therapeutic agents can be any agents having therapeutic or other value when administered to an animal, particularly to a mammal, such as drugs, nutrients, and cosmetics (cosmeceuticals). It should be understood that while the invention is described with particular reference to its value in the form of aqueous dispersions, the invention is not so limited. Thus, hydrophobic drugs, nutrients or cosmetics which derive their therapeutic or other value from, for example, topical or transdermal administration, are still considered to be suitable for use in the present invention.

Specific non-limiting examples of hydrophobic therapeutic agents that can be used in the pharmaceutical compositions of the present invention include the following representative compounds, as well as their pharmaceutically acceptable salts, isomers, esters, ethers and other derivatives:

analgesics and anti-inflammatory agents, such as aloxiprin, auranofin, azapropazone, benorylate, capsaicin, celecoxib, diclofenac, diflunisal, etodolac, fenbufen, fenoprofen calcium, flurbiprofen, ibuprofen, indomethacin, ketoprofen, ketorolac, leflunomide, meclofenamic acid, mefenamic acid, nabumetone, naproxen, oxaprozin, oxyphenbutazone, phenylbutazone, piroxicam, refocoxib, sulindac, tetrahydrocannabinol, tramadol and tromethamine;

antihelminthics, such as albendazole, bephenium hydroxynaphthoate, cambendazole, dichlorophen, ivermectin, mebendazole, oxamniquine, oxfendazole, oxantel embonate, praziquantel, pyrantel embonate and thiabendazole;

anti-arrhythmic agents, such as amiodarone HCl, disopyramide, flecainide acetate and quinidine sulfate;

anti-asthma agents, such as zileuton, zafirlukast, terbutaline sulfate, montelukast, and albuterol;

anti-bacterial agents such as alatrofloxacin, azithromycin, baclofen, benzathine penicillin, cinoxacin, ciprofloxacin HCl, clarithromycin, clofazimine, cloxacillin, demeclocycline, dirithromycin, doxycycline, erythromycin, ethionamide, furazolidone, grepafloxacin, imipenem, levofloxacin, lorefloxacin, moxifloxacin HCl, nalidixic acid, nitrofurantoin, norfloxacin, ofloxacin, rifampicin, rifabutine, rifapentine, sparfloxacin, spiramycin, sulphabenzamide, sulphadoxine, sulphamerazine, sulphacetamide, sulphadiazine, sulphafurazole, sulphamethoxazole, sulphapyridine, tetracycline, trimethoprim, trovafloxacin, and vancomycin;

anti-viral agents, such as abacavir, amprenavir, delavirdine, efavirenz, indinavir, lamivudine, nelfinavir, nevirapine, ritonavir, saquinavir, and stavudine;

anti-coagulants, such as cilostazol, clopidogrel, dicumarol, dipyridamole, nicoumalone, oprelvekin, phenindione,, ticlopidine, and tirofiban;

anti-depressants, such as amoxapine, bupropion, citalopram, clomipramine, fluoxetine HCl, maprotiline HCl, mianserin HCl, nortriptyline HCl, paroxetine HCl, sertraline HCl, trazodone HCl, trimipramine maleate, and venlafaxine HCl;

anti-diabetics, such as acetohexamide, chlorpropamide, glibenclamide, gliclazide, glipizide, glimepiride, miglitol, pioglitazone, repaglinide, rosiglitazone, tolazamide, tolbutamide and troglitazone;

anti-epileptics, such as beclamide, carbamazepine, clonazepam, ethotoin, felbamate, fosphenytoin sodium, lamotrigine, methoin, methsuximide, methylphenobarbitone, oxcarbazepine, paramethadione, phenacemide, phenobarbitone, phenytoin, phensuximide, primidone, sulthiame, tiagabine HCl, topiramate, valproic acid, and vigabatrin;

anti-fungal agents, such as amphotericin, butenafine HCl, butoconazole nitrate, clotrimazole, econazole nitrate, fluconazole, flucytosine, griseofulvin, itraconazole, ketoconazole, miconazole, natamycin, nystatin, sulconazole nitrate, oxiconazole, terbinafine HCl, terconazole, tioconazole and undecenoic acid;

anti-gout agents, such as allopurinol, probenecid and sulphin-pyrazone;

anti-hypertensive agents, such as amlodipine, benidipine, benezepril, candesartan, captopril, darodipine, dilitazem HCl, diazoxide, doxazosin HCl, elanapril, eposartan, losartan mesylate, felodipine, , fenoldopam, fosenopril, guanabenz acetate, irbesartan, isradipine, lisinopril, minoxidil, nicardipine HCl, nifedipine, nimodipine, nisoldipine, phenoxybenzamine HCl, prazosin HCl, quinapril, reserpine, terazosin HCl, telmisartan, and valsartan;

anti-malarials, such as amodiaquine, chloroquine, chlorproguanil HCl, halofantrine HCl, mefloquine HCl, proguanil HCl, pyrimethamine and quinine sulfate;

anti-migraine agents, such as dihydroergotamine mesylate, ergotamine tartrate, frovatriptan, methysergide maleate, naratriptan HCl, pizotyline malate, rizatriptan benzoate, sumatriptan succinate, and zolmitriptan;

anti-muscarinic agents, such as atropine, benzhexol HCl, biperiden, ethopropazine HCl, hyoscyamine, mepenzolate bromide, oxyphencyclimine HCl and tropicamide;

anti-neoplastic agents and immunosuppressants, such as aminoglutethimide, amsacrine, azathioprine, bicalutamide, bisantrene, busulfan, camptothecin, cytarabine, chlorambucil, cyclosporin, dacarbazine, ellipticine, estramustine, etoposide, irinotecan, lomustine, melphalan, mercaptopurine, methotrexate, mitomycin, mitotane, mitoxantrone, mofetil mycophenolate, nilutamide, paclitaxel, procarbazine HCl, sirolimus, tacrolimus, tamoxifen citrate, teniposide, testolactone, topotecan HCl, and toremifene citrate;

anti-protozoal agents, such as atovaquone, benznidazole, clioquinol, decoquinate, diiodohydroxyquinoline, diloxanide furoate, dinitolmide, furazolidone, metronidazole, nimorazole, nitrofurazone, ornidazole and tinidazole;

anti-thyroid agents, such as carbimazole, paracalcitol, and propylthiouracil;

anti-tussives, such as benzonatate;

anxiolytics, sedatives, hypnotics and neuroleptics, such as alprazolam, amylobarbitone, barbitone, bentazepam, bromazepam, bromperidol, brotizolam, butobarbitone, carbromal, chlordiazepoxide, chlormethiazole, chlorpromazine, chlorprothixene, clonazepam, clobazam, clotiazepam, clozapine, diazepam, droperidol, ethinamate, flunanisone, flunitrazepam, triflupromazine, fluphenthixol decanoate, fluphenazine decanoate, flurazepam, gabapentin, haloperidol, lorazepam, lormetazepam, medazepam, meprobamate, mesoridazine, methaqualone, methylphenidate, midazolam, molindone, nitrazepam, olanzapine, oxazepam, pentobarbitone, perphenazine pimozide, prochlorperazine, pseudoephedrine, quetiapine, rispiridone, sertindole, sulpiride, temazepam, thioridazine, triazolam, zolpidem, and zopiclone;

.beta.-Blockers, such as acebutolol, alprenolol, atenolol, labetalol, metoprolol, nadolol, oxprenolol, pindolol and propranolol;

cardiac inotropic agents, such as amrinone, digitoxin, digoxin, enoximone, lanatoside C and medigoxin;

corticosteroids, such as beclomethasone, betamethasone, budesonide, cortisone acetate, desoxymethasone, dexamethasone, fludrocortisone acetate, flunisolide, fluocortolone, fluticasone propionate, hydrocortisone, methylprednisolone, prednisolone, prednisone and triamcinolone;

diuretics, such as acetazolamide, amiloride, bendroflumethiazide, bumetanide, chlorothiazide, chlorthalidone, ethacrynic acid, frusemide, metolazone, spironolactone and triamterene.

anti-parkinsonian agents, such as bromocriptine mesylate, lysuride maleate, pramipexole, ropinirole HCl, and tolcapone;

gastrointestinal agents, such as bisacodyl, cimetidine, cisapride, diphenoxylate HCl, domperidone, famotidine, lansoprazole, loperamide, mesalazine, nizatidine, omeprazole, ondansetron HCl, rabeprazole sodium, ranitidine HCl and sulphasalazine;

histamine H, and H,-receptor antagonists, such as acrivastine, astemizole, chlorpheniramine, cinnarizine, cetrizine, clemastine fumarate, cyclizine, cyproheptadine HCl, dexchlorpheniramine, dimenhydrinate, fexofenadine, flunarizine HCl, loratadine, meclizine HCl, oxatomide, and terfenadine;

keratolytics, such as such as acetretin, calcipotriene, calcifediol, calcitriol, cholecalciferol, ergocalciferol, etretinate, retinoids, targretin, and tazarotene;

lipid regulating agents, such as atorvastatin, bezafibrate, cerivastatin, ciprofibrate, clofibrate, fenofibrate, fluvastatin, gemfibrozil, pravastatin, probucol, and simvastatin;

muscle relaxants, such as dantrolene sodium and tizanidine HCl;

nitrates and other anti-anginal agents, such as amyl nitrate, glyceryl trinitrate, isosorbide dinitrate, isosorbide mononitrate and pentaerythritol tetranitrate;

nutritional agents, such as calcitriol, carotenes, dihydrotachysterol, essential fatty acids, non-essential fatty acids, phytonadiol, vitamin A, vitamin B₂, vitamin D, vitamin E and vitamin K.

opioid analgesics, such as codeine, codeine, dextropropoxyphene, diamorphine, dihydrocodeine, fentanyl, meptazinol, methadone, morphine, nalbuphine and pentazocine;

sex hormones, such as clomiphene citrate, cortisone acetate, danazol, dehydroepiandrosterone, ethynyl estradiol, finasteride, fludrocortisone, fluoxymesterone, medroxyprogesterone acetate, megestrol acetate, mestranol, methyltestosterone, norethisterone, norgestrel, oestradiol, conjugated estrogens, progesterone, rimexolone, stanozolol, stilbestrol, testosterone and tibolone;

stimulants, such as amphetamine, dexamphetamine, dexfenfluramine, fenfluramine and mazindol;

and others, such as becaplermin, donepezil HCl, L-thryroxine, methoxsalen, verteporfrin, physostigmine, pyridostigmine, raloxifene HCl, sibutramine HCl, sildenafil citrate, tacrine, tamsulosin HCl, and tolterodine.

Preferred hydrophobic therapeutic agents include sildenafil citrate, amlodipine, tramadol, celecoxib, rofecoxib, oxaprozin, nabumetone, ibuprofen, terbenafine, itraconazole, zileuton, zafirlukast, cisapride, fenofibrate, tizanidine, nizatidine, fexofenadine, loratadine, famotidine, paricalcitol, atovaquone, nabumetone, tetrahydrocannabinol, megestrol acetate, repaglinide, progesterone, rimexolone, cyclosporin, tacrolimus, sirolimus, teniposide, paclitaxel, pseudoephedrine, troglitazone, rosiglitazone, finasteride, vitamin A, vitamin D, vitamin E, and pharmaceutically acceptable salts, isomers and derivatives thereof Particularly preferred hydrophobic therapeutic agents are progesterone and cyclosporin.

It should be appreciated that this listing of hydrophobic therapeutic agents and their therapeutic classes is merely illustrative. Indeed, a particular feature, and surprising advantage, of the compositions of the present invention is the ability of the present compositions to solubilize and deliver a broad range of hydrophobic therapeutic agents, regardless of functional class. Of course, mixtures of hydrophobic therapeutic agents may also be used where desired.

3. Solubilizers

If desired, the pharmaceutical compositions of the present invention can optionally include additional compounds to enhance the solubility of the hydrophobic therapeutic agent in the carrier system. Examples of such compounds, referred to as "solubilizers", include:

alcohols and polyols, such as ethanol, isopropanol, butanol, benzyl alcohol, ethylene glycol, propylene glycol, butanediols and isomers thereof, glycerol, pentaerythritol, sorbitol, mannitol, transcutol, dimethyl isosorbide, polyethylene glycol, polypropylene glycol, polyvinylalcohol, hydroxypropyl methylcellulose and other cellulose derivatives, cyclodextrins and cyclodextrin derivatives;

ethers of polyethylene glycols having an average molecular weight of about 200 to about 6000, such as tetrahydrofurfuryl alcohol PEG ether (glycofurol, available commercially from BASF under the trade name Tetraglycol) or methoxy PEG (Union Carbide);

amides, such as 2-pyrrolidone, 2-piperidone, .epsilon.-caprolactam, N-alkylpyrrolidone, N-hydroxyalkylpyrrolidone, N-alkylpiperidone, N-alkylcaprolactam, dimethylacetamide, and polyvinylpyrrolidone;

esters, such as ethyl propionate, tributylcitrate, acetyl triethylcitrate, acetyl tributyl citrate, triethylcitrate, ethyl oleate, ethyl caprylate, ethyl butyrate, triacetin, propylene glycol monoacetate, propylene glycol diacetate, .epsilon.-caprolactone and isomers thereof, .delta.-valerolactone and isomers thereof, .beta.-butyrolactone and isomers thereof;

and other solubilizers known in the art, such as dimethyl acetamide, dimethyl isosorbide (Arlasolve DMI (ICI)), N-methyl pyrrolidones (Pharmasolve (ISP)), monooctanoin, diethylene glycol monoethyl ether (available from Gattefosse under the trade name Transcutol), and water.

Mixtures of solubilizers are also within the scope of the invention. Except as indicated, these compounds are readily available from standard commercial sources.

Preferred solubilizers include triacetin, triethylcitrate, ethyl oleate, ethyl caprylate, dimethylacetamide, N-methylpyrrolidone, N-hydroxyethylpyrrolidone, polyvinylpyrrolidone, hydroxypropyl methylcellulose, hydroxypropyl cyclodextrins, ethanol, polyethylene glycol 200-600, glycofurol, transcutol, propylene glycol, and dimethyl isosorbide. Particularly preferred solubilizers include sorbitol, glycerol, triacetin, ethyl alcohol, PEG-400, glycofurol and propylene glycol.

The amount of solubilizer that can be included in compositions of the present invention is not particularly limited. Of course, when such compositions are ultimately administered to a patient, the amount of a given solubilizer is limited to a bioacceptable amount, which is readily determined by one of skill in the art. In some circumstances, it may be advantageous to include amounts of solubilizers far in access of bioacceptable amounts in order to maximize the concentration of hydrophobic therapeutic agent, with excess solubilizer removed prior to providing the composition to a patient using conventional techniques, such as distillation or evaporation. Thus, if present, the solubilizer can be in a concentration of 50%, 100%, 200%, or up to about 400% by weight, based on the amount of surfactant. If desired, very small amounts of solubilizers may also be used, such as 25%, 10%, 5%, 1% or even less. Typically, the solubilizer will be present in an amount of about 1% to about 100%, more typically about 5% to about 25% by weight.

4. Other Additives

Other additives conventionally used in pharmaceutical compositions can be included, and these additives are well known in the art. Such additives include antioxidants, preservatives, chelating agents, viscomodulators, tonicifiers, flavorants, colorants odorants, opacifiers, suspending agents, binders, and mixtures thereof The amounts of such additives can be readily determined by one skilled in the art, according to the particular properties desired.

5. Dosage Forms

The pharmaceutical compositions of the present invention can be provided in the form of a solution preconcentrate; i.e., a composition as described above, and intended to be dispersed with water, either prior to administration, in the form of a drink, or dispersed in vivo. Alternatively, the compositions can be provided in the form of a diluted preconcentrate (i.e., an aqueous dispersion), a semi-solid dispersion or a solid dispersion. If desired, the compositions may be encapsulated in a hard or soft gelatin capsule, a starch capsule or an enteric coated capsule. The term "enteric coated capsule" as used herein means a capsule coated with a coating resistant to acid; i.e., an acid resistant enteric coating. Although solubilizers are typically used to enhance the solubility of a hydrophobic therapeutic agent, they may also render the compositions more suitable for encapsulation in hard or soft gelatin capsules. Thus, the use of a solubilizer such as those described above is particularly preferred in capsule dosage forms of the pharmaceutical compositions. If present, these solubilizers should be added in amounts sufficient to impart to the compositions the desired solubility enhancement or encapsulation properties.

Although formulations specifically suited to oral administration are presently preferred, the compositions of the present invention can also be formulated for topical, transdermal, ocular, pulmonary, vaginal, rectal, transmucosal or parenteral administration, in the form of a triglyceride-free cream, lotion, ointment, suppository, gel or the like. If such a formulation is desired, other additives may be included, such as are well-known in the art, to impart the desired consistency and other properties to the formulation. The compositions of the present invention can also be formulated as a spray or an aerosol. In particular, the compositions may be formulated as a sprayable solution, and such formulation is particularly useful for spraying to coat a multiparticulate carrier, such as a bead. Such multiparticulate carriers are well known in the art.

6. Preparation of Pharmaceutical Compositions

The pharmaceutical compositions of the present invention can be prepared by conventional methods well known to those skilled in the art. Of course, the specific method of preparation will depend upon the ultimate dosage form. For dosage forms substantially free of water, i.e., when the composition is provided in a pre-concentrated form for later dispersion in an aqueous system, the composition is prepared by simple mixing of the components to form a pre-concentrate. The mixing process can be aided by gentle heating, if desired. For compositions in the form of an aqueous dispersion, the pre-concentrate form is prepared, then the appropriate amount of purified water is added. Upon gentle mixing, a clear aqueous dispersion is formed. If any water-soluble additives are included, these may be added first as part of the pre-concentrate, or added later to the clear aqueous dispersion, as desired.

In another embodiment, the present invention includes a multi-phase dispersion. In this embodiment, a pharmaceutical composition includes a carrier which forms a clear aqueous dispersion upon mixing with an aqueous solution, and an additional amount of non-solubilized hydrophobic therapeutic agent. Thus, the term "multi-phase" as used herein to describe these compositions of the present invention means a composition which when mixed with an aqueous solution forms a clear aqueous phase and a particulate dispersion phase. The carrier is as described above, and can include any of the surfactants, hydrophobic therapeutic agents, solubilizers and additives previously described. An additional amount of hydrophobic therapeutic agent is included in the composition. This additional amount is not solubilized by the carrier, and upon mixing with an aqueous system is present as a separate dispersion phase. The additional amount is optionally a milled, micronized, or precipitated form. Thus, upon dilution, the composition contains two phases: a clear aqueous dispersion of the hydrophilic and hydrophobic surfactants containing a first, solubilized amount of the hydrophobic therapeutic agent, and a second, non-solubilized amount of the hydrophobic therapeutic agent dispersed therein. It should be emphasized that the resultant multi-phase dispersion will not have the optical clarity of a dispersion in which the hydrophobic therapeutic agent is fully solubilized, but will appear to be cloudy, due to the presence of the non-solubilized phase. Such a formulation may be useful, for example, when the desired dosage of a hydrophobic therapeutic agent exceeds that which can be solubilized in the carrier of the present invention. The formulation may also contain additives, as described above.

One skilled in the art will appreciate that a hydrophobic therapeutic agent may have a greater solubility in the pre-concentrate carrier than in the aqueous dispersion, so that meta-stable, supersaturated solutions having apparent optical clarity but containing a hydrophobic therapeutic agent in an amount in excess of its solubility in the aqueous dispersion can be formed. Such super-saturated solutions, whether characterized as clear aqueous dispersions (as initially formed) or as multi-phase solutions (as would be expected if the meta-stable state breaks down), are also within the scope of the present invention.

The multi-phase formulation can be prepared by the methods described above. A preconcentrate is prepared by simple mixing of the components, with the aid of gentle heating, if desired. It is convenient to consider the hydrophobic therapeutic agent as divided into two portions, a first solubilizable portion which will be solubilized by the carrier and contained within the clear aqueous dispersion upon dilution, and a second non-solubilizable portion which will remain non-solubilized. When the ultimate dosage form is non-aqueous, the first and second portions of the hydrophobic therapeutic agent are both included in the pre-concentrate mixture. When the ultimate dosage form is aqueous, the composition can be prepared in the same manner, and upon dilution in an aqueous system, the composition will form the two phases as described above, with the second non-solubilizable portion of the hydrophobic therapeutic agent dispersed or suspended in the aqueous system, and the first solubilizable portion of the hydrophobic therapeutic agent solubilized in the mixed surfactant carrier. Alternatively, when the ultimate dosage form is aqueous, the pre-concentrate can be prepared including only the first, solubilizable portion of the hydrophobic therapeutic agent. This pre-concentrate can then be diluted in an aqueous system to form a clear aqueous dispersion, to which is then added the second, non-solubilizable portion of the hydrophobic therapeutic agent to form a multi-phase aqueous composition.

The amount of hydrophobic therapeutic agent included in the pharmaceutical compositions of the present invention can be any amount desired by the formulator, up to the maximum amount that can be solubilized or suspended in a given carrier system. In general, the amount of hydrophobic therapeutic agent will be about 0.1% to about 60% by weight, based on the total weight of the pharmaceutical composition. In another aspect of the invention, described below, excess hydrophobic therapeutic agent can also be added, in a multi-phase dispersion.

B. Methods of Improved Delivery

In another aspect, the present invention relates to methods of improving delivery of hydrophobic therapeutic agents in an animal by administering to the animal a dosage form of the pharmaceutical compositions described herein. Preferably the animal is a mammal, and more preferably, a human. It has been found that the pharmaceutical compositions of the present invention when administered to an animal enable the hydrophobic therapeutic agent contained therein to be absorbed more rapidly than in conventional pharmaceutical compositions. Thus, in this aspect the invention relates to a method of increasing the rate of and/or extent of bioabsorption of a hydrophobic therapeutic agent by administering the hydrophobic therapeutic agent to an animal in the pharmaceutical compositions described herein.

C. Characteristics of the Pharmaceutical Compositions

The dispersions formed upon dilution of the pharmaceutical compositions of the present invention have the following characteristics:

Rapid formation: upon dilution with an aqueous solution, the carrier forms a clear dispersion very rapidly; i.e., the clear dispersion appears to form instantaneously.

Optical clarity: the dispersions are essentially optically clear to the naked eye, and show no readily observable signs of heterogeneity, such as turbidity or cloudiness. More quantitatively, dispersions of the pharmaceutical compositions of the present invention show a mono-modal distribution of very small particles sizes, typically 20 nm or less in average diameter; absorbances of less than about 0.3, typically less than about 0.1, at 10.times.dilution; and absorbances of less than about 0.1, typically less than about 0.01, at 100.times.dilution, as described more fully in the Examples herein. In the multi-phase embodiment of the compositions described herein, it should be appreciated that the optical clarity of the aqueous carrier dispersion phase will be obscured by the dispersed particulate non-solubilized hydrophobic therapeutic agent.

Robustness to dilution: the dispersions are surprisingly stable to dilution in aqueous solution, including aqueous solutions simulating physiological fluids such as enzyme-free simulated gastric fluid (SGF) and enzyme-free simulated intestinal fluid (SIF). The hydrophobic therapeutic agent remains solubilized for at least the period of time relevant for absorption.

Triglyceride-free: It is a particular feature of the present invention that the pharmaceutical compositions are substantially triglyceride-free. The term "triglyceride" as used herein means glycerol triesters of C₆ to about C₂5 fatty acids. Unlike conventional compositions such as oil-based solutions, emulsions, and microemulsions, which rely on the solubilizing power of triglycerides, the present compositions surprisingly solubilize hydrophobic therapeutic agents using combinations of substantially triglyceride-free surfactants.

As used herein, the term "substantially triglyceride-free" means compositions which contain triglycerides, if at all, only as minor components or impurities in surfactant mixtures. It is well known in the art that commercially available surfactants often are complex mixtures of compounds. For example, one preferred surfactant is Capmul.RTM. GMO-K, a widely-used blend of glyceryl mono- and dioleates. Due to difficulties in separating complex product mixtures, however, a typical lot of Capmul.RTM. GMO-K, as reported by the manufacturer's certificate of analysis, contains the following distribution of glyceryl esters, in percent by weight based on the total weight of glyceryl esters:

In addition, the surfactant mixture in the particular lot reported contains 0.10% water and 0.95% free, unesterified glycerol. These specific percentages are expected to vary, lot-by-lot, as well, and it is expected that commercial surfactant products will generally possess similar variability, regardless of the specific major component and the specific manufacturer. Thus, the present invention does not include surfactants which contain triglycerides as an intended component. Indeed, such surfactants are not common, since triglycerides themselves have no surfactant properties. However, it should be appreciated that the present invention does not exclude the use of surfactant products which contain small amounts of triglycerides as impurities or as unreacted starting material. It is expected that commercial mixtures suitable for use in the present invention may contain as much as 5% triglycerides by weight as unintended components. Thus, "substantially triglyceride-free" should be understood as meaning free of added triglycerides, and containing less than 5%, preferably essentially 0%, triglyceride impurities.

Without wishing to be bound by theory, it is believed that the observed properties of the clear, aqueous dispersions formed by the compositions of the present invention are consistent with, and best explained by, the formation of mixed micelles of the hydrophobic and hydrophilic surfactants, with the hydrophobic therapeutic agent solubilized by the micelles. It should be emphasized that these dispersions are characterized by the properties described herein, regardless of the precise microscopic physical form of the dispersed particles. Nevertheless, in order to more fully explain the invention, and to illustrate its unexpected and important advantages, the following discussion is offered in terms consistent with the theoretical principles believed to be correct.

It is believed that the hydrophobic and hydrophilic surfactants form mixed micelles in aqueous solution. In this model, each micelle is composed of molecules (or ions) of both the hydrophilic and hydrophobic surfactants. Depending upon the detailed three-dimensional structure of the hydrophobic therapeutic agent, its distribution of polar moieties, if any, its polarizability in local regions, and other molecule-specific and complex factors, the hydrophobic therapeutic agent may be distributed in any part of the micelle, such as near the outer, more hydrophilic region, near the inner, more hydrophobic region, or at various points in between. Further, it is known that micelles exist in dynamic equilibrium with their component molecules, and it is expected that this equilibrium will include dynamic redistribution of the hydrophobic therapeutic agent.

As discussed above, triglyceride-containing formulations suffer the disadvantage that bioabsorption of the hydrophobic therapeutic agents contained therein is dependent upon enzymatic degradation (lipolysis) of the triglyceride components. The pharmaceutical compositions of the present invention, however, are substantially free of triglycerides, and thus do not depend upon lipolysis to enable release of the hydrophobic therapeutic agent for bioabsorption. The hydrophobic therapeutic agent is in a dynamic equilibrium between the free compound in solution and the solubilized compound, thus promoting rapid release.

The unique pharmaceutical compositions of the present invention present a number of significant and unexpected advantages, including:

Efficient transport: The particle sizes in the aqueous dispersions of the present invention are much smaller, typically less than 20 nm, than the larger particles characteristic of vesicular, emulsion or microemulsion phases, and the particle size distribution is mono-modal and narrow. This reduced and more uniform size enables more efficient drug transport through the intestinal aqueous boundary layer, and through the absorptive brush border membrane. More efficient transport to absorptive sites leads to improved and more consistent absorption of hydrophobic therapeutic agents.

Non-dependence on lipolysis: The lack of triglyceride components provides pharmaceutical compositions not dependent upon lipolysis, and upon the many poorly characterized factors which affect the rate and extent of lipolysis, for effective presentation of a hydrophobic therapeutic agent to an absorptive site. Such factors include the presence of composition components which may inhibit lipolysis; patient conditions which limit production of lipase, such as pancreatic lipase secretory diseases; and dependence of lipolysis on stomach pH, endogenous calcium concentration, and presence of co-lipase or other digestion enzymes. The lack of lipolysis dependence further provides transport which does not suffer from any lag time between administration and absorption caused by the lipolysis process, enabling a more rapid onset of therapeutic action and better bioperformance characteristics. In addition, pharmaceutical compositions of the present invention can make use of hydrophilic surfactants which might otherwise be avoided or limited due to their potential lipolysis inhibiting effects.

Non-dependence on bile and meal fat contents: Due to the higher solubilization potential over bile salt micelles, the present compositions are less dependent on endogenous bile and bile related patient disease states, and meal fat contents. These advantages overcome meal-dependent absorption problems caused by poor patient compliance with meal-dosage restrictions.

Superior solubilization: The surfactant combinations used in compositions of the present invention enable superior loading capacity over conventional micelle formulations. In addition, the particular combination of surfactants used can be optimized for a specific hydrophobic therapeutic agent to more closely match the polarity distribution of the therapeutic agent, resulting in still further enhanced solubilization.

Faster dissolution and release: Due to the robustness of compositions of the present invention to dilution, the hydrophobic therapeutic agents remain solubilized and thus do not suffer problems of precipitation of the therapeutic agent in the time frame relevant for absorption. In addition, the therapeutic agent is presented in small particle carriers, and is not limited in dilution rate by entrapment in emulsion carriers. These factors avoid liabilities associated with the poor partitioning of lipid solubilized drug in to the aqueous phase, such as large emulsion droplet surface area, and high interfacial transfer resistance, and enable rapid completion of the critical partitioning step.

Consistent performance: Aqueous dispersions of the present invention are thermodynamically stable for the time period relevant for absorption, and can be more predictably reproduced, thereby limiting variability in bioavailability--a particularly important advantage for therapeutic agents with a narrow therapeutic index.

Efficient release: The compositions of the present invention are designed with components that help to keep the hydrophobic therapeutic agent solubilized for transport to the absorption site, but readily available for absorption, thus providing a more efficient transport and release.

Less prone to gastric emptying delays: Unlike triglyceride-containing formulations, the present compositions are less prone to gastric emptying delays, resulting in faster absorption. Further, the particles in dispersions of the present invention are less prone to unwanted retention in the gastro-intestinal tract.

Small size: Because of the small particle size in aqueous dispersion, the pharmaceutical compositions of the present invention allow for faster transport of the hydrophobic therapeutic agent through the aqueous boundary layer.

Claim 1 of 120 Claims

What is claimed and desired to be secured by United States Letters Patent is:

1. A pharmaceutical formulation for administration of a hydrophobic lipid-regulating agent, comprising a therapeutically effective amount of the lipid-regulating agent and a carrier comprised of

(a) at least one hydrophilic surfactant selected from the group consisting of hydrophilic non-ionic surfactants, hydrophilic ionic surfactants, and combinations thereof, and

(b) at least one hydrophobic surfactant having an HLB value less than about 10 and selected from the group consisting of alcohols; polyoxyethylene alkylethers; fatty acids; glycerol fatty acid monoesters; glycerol fatty acid diesters; acetylated glycerol fatty acid monoesters; acetylated glycerol fatty acid diesters, lower alcohol fatty acid esters; polyethylene glycol fatty acid esters; polyethylene glycol glycerol fatty acid esters; polypropylene glycol fatty acid esters; polyoxyethylene glycerides; lactic acid derivatives of monoglycerides; lactic acid derivatives of diglycerides; propylene glycol diglycerides; sorbitan fatty acid esters; polyoxyethylene sorbitan fatty acid esters; polyoxyethylene-polyoxypropylene block copolymers; transesterified vegetable oils; sterols; sterol derivatives; sugar esters; sugar ethers; sucroglycerides; polyoxyethylene vegetable oils; polyoxyethylene hydrogenated vegetable oils, reaction products of polyols and at least one member of the group consisting of fatty acids, glycerides, vegetable oils, hydrogenated vegetable oils, and sterols; and mixtures thereof,

said hydrophilic and hydrophobic surfactants being present in amounts such that upon dilution with an aqueous solution at an aqueous solution to carrier ratio of 100:1 by weight, the carrier forms a clear aqueous dispersion having an absorbance of less than about 0.1 at a wavelength of about 400 nm, and wherein the composition is substantially free of glycerol triesters of C₆ to about C₂5 fatty acids.
 

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