WO1994007472A1

WO1994007472A1 - Pharmaceutical compositions containing nonionic surfactants

Info

Publication number: WO1994007472A1
Application number: PCT/US1993/008107
Authority: WO
Inventors: William J. Curatolo; Michael J. Gumkowski; Julian B. Lo
Original assignee: Pfizer Inc.
Priority date: 1992-10-02
Filing date: 1993-09-02
Publication date: 1994-04-14
Also published as: IL107084A0; FI934317A; AU5095393A; JPH07507565A; FI934317A0; TW253838B; KR950703333A; HU9302774D0; EP0662826A1; MX9306125A; ZA937268B; CA2145763A1; HUT69400A

Abstract

Pharmaceutical compositions comprise an enzymatically labile pharmaceutically active agent which is permeable through the intestinal wall or requires an intestinal permeability enhancer to permeate the intestinal wall, and at least one nonionic surfactant which is capable of protecting said active agent against deactivation by enzymes. A method for the inhibition of the degradation of an enzymatically labile pharmaceutically active agent by gastrointestinal enzymes comprises combining said agent with a nonionic surfactant.

Description

PHARMACEUTICAL COMPOSITIONS CONTAINING NONIONIC SURFACTANTS

Background of the Invention This invention relates to pharmaceutical compositions containing nonionic surfactants, to methods for the inhibition of the degradation of certain pharmaceutically active agents by combining them with nonionic surfactants, and to methods of co- administering said active agents and said nonionic surfactants.

The co-administration of a pharmaceutically active agent with a surfactant is mentioned in Swenson and Curatolo, Advanced Drug Delivery Reviews, 8, 39-92 (1992). The surfactant is described as enhancing the permeability of a drug through the intestinal wall. United States Patent No. 4,579,730 suggests that the ionic bile salt sodium cholate, which is a surfactant, functions as a protease inhibitor in the small intestines so promoting absorption of insulin. The general use of surfactants as protease inhibitors in the gastrointestinal tract is not suggested.

The use of non-surfactant protease inhibitors as protectants against gastrointestinal proteases has been described in Lee, J. Controlled Release, 13(1990)213-223, Zi et al, Biochem. Pharmacol., 36(1987)1035-1039, and U.S. Patent 4,579,730. Hayakawa et al, Life Sciences 45,167-174(1989), reports that the bile salt sodium glycocholate and the nonionic surfactant polyoxyethylene-9-lauryl ether either inhibit or stimulate degradation of insulin by nasal homogenates, depending on the concentration of the surfactants. European Patent Publication No. 332,222 discloses that the protease activity of vaginal washings is decreased in the presence of the anionic surfactant sodium dodecyl sulfate and also discloses a method of vaginal coadministration of an ionic or nonionic surfactant with a biologically active polypeptide to inhibit vaginal protease at the site of administration. In accordance with the invention, pharmaceutical compositions for oral administration are provided comprising an enzymatically labile pharmaceutically active agent which is permeable through the intestinal wall and at least one nonionic surfactant which is capable of protecting said active agent against deactivation by enzymes. In one embodiment of the invention, the active agent is a peptide having a molecular weight of less than about 3,000. Examples of suitable nonionic surfactants are ethoxylated alcohols, ethoxylated fatty acids, sorbitan derivatives and ethoxylated alkyl phenols, specifically ethoxylated lauric acid, polyoxyethylene(40)stearate, polyoxyethylene(20)sorbitan monooleate, polyoxyethylene(23)lauryl ether, nonylphenoxypoly(ethyleneoxy)ethanol-30, nonylphenyoxypoly(ethyleneoxy)ethanol- 50, or a mixture of glylceryl and polyethylene glycol-1500 esters of palm kernel oil. In another embodiment of the invention, an oil is included in the composition.

Examples of suitable oils are monoglycerides, e.g., mono-octanoin or monodecanoin, diglycerides, e.g., glyceryl-1 ,2-dioctanoate, and triglycerides, e.g., vegetable oil or caprylic/capric triglyceride.

The invention also provides a pharmaceutical composition for oral administration comprising (1 ) an enzymatically labile pharmaceutically active agent which is permeable through the intestinal wall only in the presence of an intestinal permeability enhancer, (2) at least one nonionic surfactant which is capable of protecting said active agent against deactivation by proteolytic enzymes and which is not an intestinal permeability enhancer, and (3) an intestinal permeability enhancer which is other than said nonionic surfactant. In one embodiment, this composition comprises a nonionic surfactant having an HLB of about 14 to about 20.

The invention also provides a pharmaceutical composition for oral administration comprising (1) an enzymatically labile pharmaceutically active agent which exerts its therapeutic activity locally in the stomach or intestine, and (2) at least one nonionic surfactant which is capable of protecting said active agent against deactivation by enzymes.

The invention further provides a method for inhibition of the enzymatic degradation of an enzymatically labile pharmaceutically active agent which is permeable through the intestinal wall by combining said active agent with a nonionic surfactant which is capable of protecting said active agent against deactivation by enzymes.

The invention also provides a method for the oral administration of an enzymatically labile pharmaceutically active agent which is permeable through the intestinal wall to a host which comprises co-administering to said host said active agent and at least one nonionic surfactant capable of protecting said active agent against deactivation by enzymes.

The invention yet further provides for a method for the oral administration of an enzymatically labile pharmaceutically active agent which is permeable through the intestinal wall only in the presence of an intestinal permeability enhancer by co- administering to said host said active agent, at least one nonionic surfactant which is capable of protecting said active agent against deactivation by enzymes and which is not an intestinal permeability enhancer, and an intestinal permeability enhancer which is other than said nonionic surfactant. The enzymatically labile pharmaceutically active agents of the invention contain enzymatically labile bonds, such as ester, amide and/or peptide bonds, and are inactivated by digestive enzymes in the gastrointestinal tract. Examples of such digestive enzymes are pepsin, trypsin, chymotrypsin, elastin, aminopeptidase, carboxypeptidase, lipase and intestinal glycosidases and esterases. Examples of enzymatically labile pharmaceutically active agents (the active agents) are calcitonin, prolactin, adrenocorticotropin, thyrotropin, growth hormone, gonadotropic hormone, oxytocin, vasopressin, gastrin, tetragastrin, pentagastrin, glucagon, insulin, secretin, substance P, gonadotropin, leutinizing hormone releasing hormone, leuprolide, enkephalin, follicle stimulating hormone, cholecystokinin, thymopentin, endothelin, neurotensin, interferon, interleukins, insulinotropin, and therapeutic antibodies; and analogues of the above agents, which possess D-amino acids, blocked amino or carboxyl end groups e.g., nafarelin acetate and YdAGFdL (an enlaphalin analogue), and non-natural amino acids such as S-methyl cysteine and statine. Also included are purified extracts of natural origin and their chemical modifications, as well as products obtained by tissue culture and products obtained by cultivating microorganisms or cells rendered productive by genetic engineering techniques. Also included are synthetic peptides and derivatized synthetic peptides such as terlakiren (isopropyl-N-[N-(4-morpholine-carbonyl)-L-phenylalanine-S-methyl- cysteine]-2(R)-hydroxy-3(S)-amino-4-cyclohexylbutanoate) disclosed in U.S. Patent 4,814,342, Example 4 thereof, which is incorporated herein by reference. Further included are prodrugs of the active agents, i.e., derivatives of the active agent which convert to the active agent in vivo.

The active agents further include prodrugs of a pharmaceutically active compound which itself may not contain an enzymatically labile bond. Such prodrugs are themselves enzymatically labile by connection of the prodrug group to the pharmaceutically active compound through an enzymatically labile bond such as an ester or amide bond. According to the invention, when the active agent is permeable through the intestinal wall, it is co-administered with at least one nonionic surfactant which is capable of protecting the active agent against deactivation by enzymes. The nonionic surfactant is used in an amount which is effective in protecting the active agent against deactivation by enzymes.

In general, an active agent or prodrug is considered permeable through the intestinal wall if it can permeate the intestinal wall without the aid of a permeability enhancer. The intestinal permeability of the enzymatically labile active agent or prodrug is determined by perfusion of a solution of the active agent or prodrug through a segment of the intestine of an anesthetized rat. This test must be carried out in the absence of digestive enzymes to reduce enzymatic degradation of the tested active agent or prodrug. The intestinal segment therefore must be properly washed before the test or the test must be in the presence of inhibitors of digestive enzymes, such as Bowman-Birk trypsin/chymotrypsin inhibitor. For the purposes of the invention, the enzymatically labile active agent or prodrug is considered permeable through the intestinal wall when it has a P_w greater than about 3.5 X 10^'6 cm/sec. The P_w of a compound may be determined from the following equation:

K_A = A x_P_βpp (1) V wherein K_A is the absorption rate constant of the compound, A is the surface area of the intestinal segment, and V is the volume of the intestinal segment. When the intestinal segment is cylindrical and the intestinal radius is about 0.2 cm, as in the rat,

A/V is about 10 cm^'1. The absorption rate constant K_A for a compound is calculated in the rat intestinal permeability test from the following equation:

K_A = Qύ C (2)

V wherein C, is the concentration of the compound at the start of the test, C₀ is the concentration of the compound in the perfusate after passage through a 22 cm intestinal segment, Q is the flow rate and V is the volume of the ntestinal segment, as mentioned above. Terlakiren is an example of an enzymatically labile drug which has good intestinal permeability, and does not require a permeability enhancer to achieve significant oral absorption. Terlakiren has a K_A of 0.02 min^'1 , a P_w of 3.3 x 10^"5 cm/sec, and an aqueous solubility of 0.08 mg/ml. Friedman and Amidon, Pharmaceutical Research, 8,93-96 (1990), assesses the permeability of the pentapeptides Leu-enkephalin and Leu-D(Ala)₂-enkephalin using the rat intestinal perfusion model. Analysis of the data in the reference using the above equations (1 ) and (2) results in a P_w value of 1.3 X 10^"3 cm/sec for both enkephalins. These compounds are thus permeable under the definition of permeability of the invention. These compounds are also enzymatically labile. An example of an enzymatically labile compound which is impermeable under the above definition of permeability according to the invention is insulin having a P_w of 4.97 X 10^"7 cm/sec.

In general, the coadministration of nonionic surfactants with an enzymatically labile pharmaceutically active agent or prodrug will protect the agent or prodrug from enzymatic hydrolysis when the surfactant and the agent or prodrug are coadministered orally, rectally, nasally, or vaginally.

Examples of permeable active agents are peptides with a molecular weight of less than about 3,000 and more than about 200, which are passively absorbed by the intestinal wall, and dipeptides having a molecular weight of about 200, which are actively transported. As the polarity of the peptide decreases, its permeability increases. However, above a molecular weight of about 2000 to about 3000, permeation will not generally occur without the aid of a permeability enhancer. Specific examples of peptides having a molecular weight of less than about 2,000 and therefore being permeable, are oxytocin, vasopressin, leutinizing hormone releasing hormone, leuprolide, enkephalin, thymopentin, octreotide, thyrotropin releasing hormone, CCK-8, bradykinin, angiotensin I, somatostatin, desmopressin, substance P, and gonadotropin releasing hormone. Specific examples of peptides having a molecular weight of about 3,000, and therefore being slowly permeable, are calcitonin, glucagon, secretin, endorphin, and insulinotropin. Examples of active agents which exert their therapeutic activity locally in the stomach or small intestine are anti-ulcer medications such as -sucralfate, cholesterol lowering agents such as cholestyramine, hormones such as gastrin and cholecystokinin, antibiotics and other therapeutic agents. Those surfactants which are capable of protecting the active agent against deactivation by enzymes (protective surfactants) may be identified by an in vitro enzyme inhibition assay as described in Examples 1 , 2 and 11.

Examples of more preferred protective nonionic surfactants are as follows:

Examples of preferred nonionic surfactants are as follows:

An oil may be coadministered with the active agent and the protective nonionic surfactant. In the context of the invention, an oil is a liquid which is immiscible with water. The oil may aid in solubilization of the active agent where the active agent is non-polar. In some cases, the oil may also be a protective surfactant, for instance Capmul-MCM (monooctanoin). Other suitable oils include triglycerides, diglycerides, and monoglycerides. The monoglycerides, e.g., mono-olein, and mono-octanoin (Capmul MCM; lmwitor-308), are unusual in that they are polar oils, compared to di- and tri-glycerides, and, can also be surfactants or emulsifiers. The monoglycerides may serve as emulsifiers when mixed with non-polar oils such as triglyceride vegetable oils or medium chain C₄-C₁₂ triglycerides such as Miglyol-812. When the monoglyceride is the protective surfactant of the formulation, the monoglyceride serves as the water- immiscible oil phase. In that case, an additional surfactant/emulsifier may be included to emulsify the monoglyceride oil in the aqueous use environment. When an additional surfactant/emulsifier is not present, the monoglyceride can serve both as oil phase and surfactant/emulsifier. For example, when mono-octanoin (Capmul-MCM) is released in an aqueous use environment, it serves both as an oil and a surfactant/emulsifier.

Suitable combinations of surfactant and oil include Tween-80 with Miglyol-812 or Capmul-MCM, and Labrafil-M-1944CS with Miglyol-812. Mixtures of more than two surfactants and oils are possible. For example, Tween-80 and Capmul-MCM may be combined with Miglyol-812.

Suitable oils for use in this invention are:

According to the invention, an active agent, which is permeable through the intestinal wall only in the presence of an intestinal permeability enhancer (non- permeable active agent) is co-administered with at least one protective nonionic surfactant which is not a permeability enhancer (non-enhancer protective surfactant), and a permeability enhancer which is not the protective nonionic surfactant.

In general, non-permeable active agents do not disappear from the perfusion fluid after about one hour in the above described permeability test. Examples of such active agents are peptides of a molecular weight of more than about 3,000, e.g., prolactin, growth hormone, insulin, gonadotropin, follicle stimulating hormone, interferons, interleukins and therapeutic antibodies. The ability of a nonionic surfactant to enhance the permeability of a non- permeable active agent may be determined by the following test. A segment of the intestine of an anesthetized rat is externalized, and a solution of the poorly absorbed drug phenol red and the nonionic surfactant to be tested is pumped through the intestinal segment for one hour. At the end of the one hour perfusion, systemic blood is collected and the drug concentration therein is measured, e.g., by high performance liquid chromatography. This test was applied to a series of nonionic nonylphenoxypoly- oxyethylene (NP-POE) surfactants having from 9 to 100 POE units. These surfactants have the non-polar NP segment and the polar POE segment. The more oxyethylene (OE) units, the more polar the surfactant. It was found that the less polar surfactants having 9 to 20 OE units are permeability enhancers, whereas the more polar surfactants having 30 to 100 OE units are not. This is illustrated in Table A, which presents plasma phenol red levels at the end of a one hour rat intestinal perfusion with phenol red in the presence of 1% (gm/100 ml) NP-POE-9, -10.5, -20, -30, -50, -100.

Table A

One method of measuring the polarity of nonionic surfactants is by determining the hydrophile-lipophile balance (HLB), Griffin, J. Soc. Cosmet. Chem., 5, 249-256 (1954). For NP-POE's, those surfactants having an HLB of less than 17 are permeability enhancers and those having an HLB of more than 17 are not. Similarly, for mixtures of NP-POE's of different POE lengths, the HLB of 17 or less is essential for permeability enhancement. The HLB of 17 or less is not essential to the permeability enhancement of all structural classes of surfactants. For example, the nonionic surfactant polysorbate-80 (Tween-80; POE-sorbitan-monooleate) having an HLB of 15 is not a permeability enhancer in the phenol red perfusion test. For the POE-sorbitan esters, the HLB for permeability enhancement is less than 15; surfactants of this structural class with an HLB of greater than about 15 are not permeability enhancers. In yet another structural class, Gelucire 44/14, with an HLB of 14, is not a permeability enhancer, but is an effective peptide protecting agent. Examples of nonionic surfactants which are peptide protecting agents but are not permeability enhancers are NP-POE-30 (Igepal CO-880), NP-POE-50 (Igepal CO-970), NP-POE-100 (Igepal CO-990), Gelucire 44/14, and polysorbate-80.

In a typical embodiment of the invention, a soft gelatin capsule contains 50 mg of the active agent, 640 mg oil (Capmul-MCM), and 160 mg surfactant (polysorbate 80). In another typical embodiment, a #00 hard gelatin capsule contains 50 mg drug and 650 mg surfactant (Gelucire 44/14). The quantity of surfactant or surfactant plus oil in a dosage form of this invention can vary widely. However, a single unit dosage form will contain from about 1 mg to about 500 mg of the active agent, and from about 25 mg to about 1000 mg surfactant or surfactant plus oil. The following Examples illustrate the invention. EXAMPLE 1

The chymotrypsin inhibition by surfactants was demonstrated in vitro with respect to terlakiren. Control solutions were made of 0.06 mM terlakiren in isotonic buffer. A chymotrypsin solution in 0.001 N hydrogen chloride was added to give a final chymotrypsin concentration of 0.25 μM or 2.5 μM. The initial concentration of terlakiren and its concentration at various time points were analyzed by HPLC. Test solutions containing 1 % and 5% by weight surfactant and 0.06 mM terlakiren in isotonic buffer were made and the above chymotrypsin solutions were added. The concentrations of terlakiren before and during the reaction were analyzed, as summarized in Table 1. The initial rate of the degradation was determined by the slope of concentration vs. time plot. Table

EXAMPLE 2 A standard procedure was employed to assess the |n vitro potency of surfactants mixed with oils, which formed emulsions when mixed with water, vs chymotrypsin degradation of terlakiren. Terlakiren was dissolved in acetonitrile and added to a solution or dispersion of excipients (at concentrations of 0.2 or 1%, gm/100 ml) in a pH 6.5 isotonic citrate-phosphate buffer. The drug (0.065 mM) concentration was assayed. Chymotrypsin was then added to start the reaction. The solution was placed into a 37 °C water bath and sampled at 5, 10, 15, 20, 25, 30, 35, 40, and 45 minutes. The reaction was quenched using the pH 2.5 mobile phase. The samples were then assayed by reverse phase high performance liquid chromatography of terlakiren using a Water Novapak C-18 column. The mobile phase was a water: acetonitrile (50:50) mixture to which was added 1 ml of phosphoric acid per liter.

The results in Table II demonstrate that the oil/surfactant emulsions reduced the chymotrypsin-catalyzed degradation of terlakiren.

The emulsion vehicles tested were:

Vehicle A: Capmul-MCM/Polysorbate-80 (80/20)

Vehicle B: Capmul-MCM/Miglyol-812/Polysorbate-80 (40/40/20)

Vehicle C: Capmul-MCM

Vehicle D: Capmul-MCM/Polysorbate-80/Ethanol (57/38/5)

Table II

EXAMPLE 3 Experiments to determine the bioavailability of terlakiren in dogs in this Example and Examples 4 to 10 were conducted in the following manner. Beagle dogs were orally dosed with terlakiren capsules, followed by gavage with 150 ml H₂O. Serum levels of terlakiren were measured at six time points post-dose: 15 minutes, 30 minutes, 1 hour, 2 hours, 3 hours, and 4 hours. Each dog served as its own control on a preceding week. Serum was extracted with N-butyl chloride followed by incubation with an aqueous solution of chymotrypsin. The degradation product was assayed, after derivitization with fluorescamine. The fluorescence detector was a Spectroflow 280. The column was Novapak C-18. The emission wavelength was 380 nm. The mobile phase was 75:25 wateπacetonitrile and flow rate 1.0 ml/minute. The detection limit was 10 ng/ml. As a measure of drug bioavailability, zero-to-four-hour areas under curves (AUC) were calculated from the concentration-vs-time plots for each dog using the trapezoidal rule. Terlakiren (0.5053 g) was dissolved in 100% ethanol, and the solution was then added to molten Gelucire 44/14 (6.53 g) with stirring. Gelucire is a mixture of glyceryl and polyethylene glycol (PEG) 1500 esters of fatty acids from palm kernel oil, having a melting point of 44 °C and an HLB of 14. This mixture was heated at 50 °C to remove ethanol from the mixture to obtain a clear solution of 7.18% by weight terlakiren in Gelucire 44/14. Capsules (#00) were each filled with 700 mg of the Gelucire 44/14 solution. Two capsules (100 mg of terlakiren) were dosed in each of the 4 dogs. Blood levels of the drug over 4 hours postdose were analyzed. The area-under-the- curve (AUC) of each dog's blood level was calculated and compared with that of a 100 mg powder-filled capsule in the same dog. The average improvement in bioavailability of this formulation over the solid capsules was 22 fold.

EXAMPLE 4 Terlakiren (one part) was mixed and milled with molten Gelucire (5 parts) in an Attritor mill for 5 hours to give a homogeneous dispersion. Hard gelatin capsules (#0) were filled with 600 mg of the dispersion which contained 100 mg of terlakiren. In a group of 4 dogs (2 males and 2 females), each dog was dosed with one capsule. The average improvement in bioavailability due to Gelucire 44/14 was 21 fold, compared to powder-filled capsule. EXAMPLE 5 By a process similar to the one described in Example 4, 100 mg of terlakiren was mixed with 500 mg of Myrj 52 and filled into #0 capsules. Myrj 52 is a mixture of polyoxyethylene mono-esters and di-esters of stearic acid, the average polymer length being about 40 oxyethylene units. The AUC's of 4 dogs were compared. The average improvement in bioavailability due to Myrj 52 was 14 fold, compared to powder-filled capsule.

EXAMPLE 6 By a process similar to the one described in Example 4, 100 mg of terlakiren was mixed with 500 mg of Acconon 1000 ML and filled into #0 capsules. Acconon PEG 1000 ML is PEG (1 ,000 molecular weight) ethoxylated lauric acid, having a melting point of 37.3°C and an HLB value of 16.5. The AUC's of 4 dogs were compared. The average improvement in bioavailability due to Acconon 1000 ML was 10 fold, compared to powder-filled capsules. EXAMPLE 7

Terlakiren (1 part) and Gelucire 44/14 (5 parts) were mixed and milled in a Dynomill for 8 minutes to give a homogeneous dispersion. The particle size of terlakiren was greatly reduced. Capsules containing 600 mg of this dispersion (100 mg terlakiren) were tested in both dogs and humans. The improvements in bioavailability due to Gelucire 44/14 are 14 fold in 4 dogs and 2.8 fold in 11 healthy volunteers, compared to powder-filled capsules.

EXAMPLE 8

Terlakiren (1 part) and Gelucire 44/14 (5 parts) were mixed and homogenized without any particle size reduction to give a homogeneous dispersion. Capsules containing 600 mg of this dispersion (100 mg terlakiren) were tested in both dogs and humans. The improvement in bioavailability due to Gelucire 44/14 were 1.7 fold in 4 dogs and 2.3 fold in 11 healthy human volunteers, compared to powder-filled capsules.

EXAMPLE 9 Formulations of terlakiren in surfactants mixed with oils, which formed emulsions when mixed with water, were administered to dogs. Each dog received a 100 mg dose of terlakiren. Tables III and IV give the content of the formulations including the control powder-filled capsule formulation (Powder) which does not contain protective surfactants.

Table V presents the mean AUC for each formulation and the mean fold- improvement over the powder-filled capsule.

Table III Formulations of Terlakiren in a Surfactant and in Mixtures of Oils with Surfactants

(mg per unit dosage form)

Table IV

Formulations of Terlakiren Containinq Mixtures of Oil and Surfactant

(in mg per unit dosage form)

Table V

Bioavailability of Terlakiren in Beagle Dogs Following Oral

Administration of a 100 mg Dose

EXAMPLE 10 Formulations of terlakiren in surfactants mixed with oils, which formed emulsions when mixed with water, were also administered to human volunteers. The compositions of the formulations were the same as those shown in Table III. Each volunteer received a 100 mg dose of terlakiren. The AUC results are given in Table VI. The results show that surfactants mixed with oils yielded an improvement in bioavailability of terlakiren relative to the powder-filled capsules containing none of the protecting agents. Table VI

Bioavailability of Terlakiren in Human Volunteers Following Oral Administration of a 100 mg Dose in Four Different Formulations

* Only 11 of the subjects were included in this calculation, since in one subject no serum levels of terlakiren were detected following administration of the powder-filled capsule.

EXAMPLE 11 The in vitro trypsin inhibition by surfactants was assessed with benzoyl-arginine- para-nitroanilide (BAPNA) as the enzymatically labile active agent. Test solutions of 1.25 μg/ml trypsin (103 benzoyl arginine ethyl ester units/ml), 0.5 mg/ml BAPNA, and 0.5 mg/ml surfactant were prepared in a buffer of 0.048 M TRIS and 0.019 M calcium chloride having a pH of 8 and containing 3.75 g/ml bovine serum albumin. These test solutions were incubated at 37 °C. Samples were taken after 5 minutes and then at 5 minute intervals to 40 minutes, and quenched with an equal volume of 30% by volume of acetic acid before analysis. The decay product of BAPNA hydrolysis, 4-nitroaniline, was analyzed with a Perkin-Elmer Lambda 3B UV/Vis spectrophotometer. The absorbance of the quenched samples was measured at 410 nm. The percentage inhibition of BAPNA degradation was calculated based on a comparison with a control which did not contain a surfactant, as follows:

% inhibition = 100% x [1-(S/S₀)] wherein S_j is the rate of change of absorbance with time in the presence of a surfactant, and S₀ is the rate of change of absorbance with time in the absence of a surfactant. The results in Table VII demonstrate that the tested surfactants reduced the trypsin-catalyzed degradation of BAPNA. Table VII

Example 12 The in vitro chymotrypsin inhibition by surfactants was assessed with benzolytyrosine ethyl ester (BTEE) as a model for an esterified drug or prodrug the hydrolysis of which is catalyzed by chymotrypsin. Test solutions of 0.6 microgram/ml chymotrypsin, 0.43 micromolar BTEE, and 3 or 10 mg/ml surfactant were prepared in a 0.034 M Tris HCI buffer containing 0.43 M calcium chloride having a pH of 7.8. The studies were performed at room temperature.

The progress of the hydrolysis of BTEE was monitored with a Perkin-Elmer Lambda 3B UV/Vis spectrophotometer. The reaction mixture was introduced into a cuvette which was placed into the spectrophometer for direct reading of absorbance at 256 nm as a function of time.

Table VIII lists the percent of BTEE remaining after 10 minutes and the results demonstrate that the tested surfactants reduced the chymotrypsin-catalyzed hydrolysis of BTEE. Tabel VIII

Composition % of BTEE remaining after 10 minutes

Control 19 Polysorbate 80 0.3% 23

Polysorbate 80 1% 36

Control 19

Myrj 52S 0.3% 26 Myrj 52S 1% 37

Claims

1. A pharmaceutical composition for oral administration comprising an enzymatically labile pharmaceutically active agent which is permeable through the intestinal wall and at least one nonionic surfactant which is capable of protecting said active agent against deactivation by enzymes.

2. A composition according to claim 1 wherein the active agent is a peptide having a molecular weight of less than about 3,000.

3. A composition according to claim 1 or 2 wherein said nonionic surfactant is an ethoxylated alcohol, an ethoxylated fatty acid, a sorbitan derivative, an ethoxylated alkyl phenol, or a monoglyceride.

4. A composition according to claim 3 wherein said nonionic surfactant is ethoxylated lauric acid, polyoxyethylene(40)stearate, polyoxyethylene(20)sorbitan monooleate, polyoxyethylene(23)lauryl ether, nonylphenoxypoly(ethyleneoxy)- ethanol-30, nonylphenoxypoly(ethyleneoxy)ethanol-50, or a mixture of glyceryl and polyethyleneglycol-1500 esters of palm kernel oil, mono-octanoin, monodecanoin, or mono-olein.

5. A composition according to anyone of claims 1 to 4 wherein an oil is included.

6. A composition according to claim 5 wherein said oil is a monoglyceride, a diglyceride, or a triglyceride.

7. A composition according to claim 6 wherein said triglyceride is a vegetable oil or caprylic/capric triglyceride, said monoglyceride is mono-octanoin or monodecanoin, and said diglyceride is glyceryl-1 ,2-dioctanoate.

8. A pharmaceutical composition for oral administration comprising (1 ) an enzymatically labile pharmaceutically active agent which is permeable through the intestinal wall only in the presence of an intestinal permeability enhancer, (2) at least one nonionic surfactant which is capable of protecting said active agent against deactivation by enzymes and which is not an intestinal permeability enhancer, and (3) an intestinal permeability enhancer which is other than said nonionic surfactant.

9. A composition according to claim 8 wherein the nonionic surfactant has an HLB of about 14 to about 20.

10. A composition according to claim 9 wherein said nonionic surfactant is an ethoxylated alcohol, an ethoxylated fatty acid, a sorbitan derivative, an ethoxylated alkyl phenol, or a monoglyceride.

11. A composition according to claim 10 wherein said nonionic surfactant is ethoxylated lauric acid, polyoxyethylene(40)stearate, polyoxyethylene(20)sorbitan monooleate, polyoxyethylene(23)lauryl ether, or nonylphenoxypoly(ethyleneoxy)- ethanol-30, nonylphenoxypoly(ethyleneoxy)ethanol-50, a mixture of glyceryl and polyethyleneglycol-1500 esters of palm kernel oil, mono-octanoin, monodecanoin, or mono-olein.

12. A composition according to claim 8 where the active agent is a polypeptide of molecular weight of about 150 to about 150,000.

13. A method for the inhibition of the degradation of an enzymatically labile pharmaceutically active agent which is permeable through the intestinal wall by enzymes which comprises combining said active agent with a nonionic surfactant which is capable of protecting said active agent against deactivation by enzymes.

14. A method according to claim 13 wherein said active agent is a peptide with a molecular weight of less than about 3,000.

15. A method according to claim 13 wherein said nonionic surfactant is an ethoxylated alcohol, an ethoxylated fatty acid, a sorbitan derivative, an ethoxylated alkyl phenol, or a monoglyceride.

16. A method according to claim 13 wherein said nonionic surfactant is ethoxylated lauric acid, polyoxyethylene(40)stearate, polyoxyethylene(20)sorbitan monooleate, polyoxyethylene(23)lauryl ether, or nonylphenoxypoly(ethyleneoxy)- ethanol-30, nonylphenoxypoly(ethyleneoxy)ethanol-50, or a mixture of glyceryl and polyethyleneglycol-1500 esters of palm kernel oil, mono-octanoin, monodecanoin or mono-olein.

17. A method for the oral administration of an enzymatically labile pharmaceutically active agent which is permeable through the intestinal wall to a host which comprises co-administering to said host said active agent and at least one nonionic surfactant capable of protecting said active agent against deactivation by enzymes.

18. A method for the oral administration of an enzymatically labile pharmaceutically active agent which is permeable through the intestinal wall only in the presence of an intestinal permeability enhancer which comprises co-administering to said host said active agent, at least one nonionic surfactant which is capable of protecting said active agent against deactivation by enzymes and which is not an intestinal permeability enhancer, and an intestinal permeability enhancer which is other than said nonionic surfactant.

19. A pharmaceutical composition for oral administration comprising an enzymatically labile pharmaceutically active agent which exerts its therapeutic activity locally in the stomach or intestine, and at least one nonionic surfactant which is capable of protecting said active agent against deactivation by enzymes.