HYDROCORTISONE AND PRAMOXINE TOPICAL FORMULATIONS HAVING ENHANCED IN-VITRO RELEASE

Technical field:

The present invention relates to pharmaceutical compositions comprising hydrocortisone and pramoxine with at least one emollient/ emulsifying agent, at least one antimicrobial perservative, at least one surfactant, at least one solvent and at least one penetration enhancer which facilitate the in-vitro release of the drug components into the skin. It also relates to methods of using the same.

Prior Art:

Hydrocortisone acetate is the synthetic acetate salt form of hydrocortisone, a corticosteroid with a molecular formula of C23H32O6. It is used for anti-inflammatory and anti-pruritic agents. It is a white to off-white crystalline powder insoluble in water and slightly soluble in alcohol and in chloroform. The chemical name is pregn-4-ene-3, 20- dione, 21-(acetyloxy)-11 , 17-dihydroxy-,(11-beta)- and the chemical structure formula is represented by Formula I (shown below).

Formula (I)

Hydrocortisone acetate is a low potency synthetic corticosteroid with antiinflammatory, antipruritic, and vasoconstrictive properties. It depresses formation, release, and activity of endogenous mediators of inflammation, including prostaglandins, kinins, histamine, liposomal enzymes, and complement system; modifies body's immune response. Pramoxine is in a class of medications called topical anesthetics. Its molecular formula is C17H27NO3, chemical name of which is 4-(3-(p-butoxyphenoxy) propyl)morpholine. The chemical structure formula of pramoxine hydrochloride is represented by Formula II (shown below);

Formula (II)

Most local anesthetics have a lipophilic aromatic group and hydrophilic amine group, linked by an intermediate chain, usually an ester or amide. Pramoxine, however, has a morpholine moiety acting as the linkage ether making it structurally unique, with good potency and considerably fewer side effects (rare sensitizing potential and decreased cross-reactivity). Pharmacokinetically, it works well as a surface anesthetic, well tolerated on the skin and delicate mucous membranes with extremely low acute and subacute toxicity.

Pramoxine and particularly, its hydrochloride salts (pramoxine HCI), provides superior analgesic properties and is readily absorbed by the skin when used as a topical anesthetic. It works by interfering with pain signals sent from the nerves to the brain. It is used to treat pain or itching caused by insect bites, minor burns or scrapes, hemorrhoids, and minor skin rash, dryness, or itching. Pramoxine is an FDA-approved drug (since 1953), long in use in various subspecialties such as obstetrics (postepisiotomy pain relief), surgery (hemorrhoids), and dentistry. The reference products are compositions obtained in topical form, namely Pramosone® Cream 2.5% (Ferndale Healthcare) containing hydrocortisone acetate 2.5% (w/w) and pramoxine hydrochloride 1 % (w/w); and Pramosone® Cream 1% containing hydrocortisone acetate 1% (w/w) and pramoxine hydrochloride 1% (w/w). The products are in a hydrophilic cream base containing stearic acid, cetyl alcohol, Aquaphor®, isopropyl palmitate, polyoxyl 40 stearate, propylene glycol, potassium sorbate, sorbic acid, triethanolamine lauryl sulphate, and purified water.

Anorectal disorders are widespread and include a number of different conditions, such as hemorrhoids, anal fissures, anal pruritus and other local anorectal lesions. Currently, there are a number of topically applied formulations for the treatment of anorectal conditions, including ointments (creams, gels, jellies and pastes), foams, sprays and medicated pads.

U.S. 5,961,997 discloses an antipruritic composition comprising menthol, camphor and phenol in a carrier. The composition preferably further comprises lidocaine and pramoxine and more preferably further comprise lidocaine, pramoxine and hydrocortisone acetate. The composition relieves itching in patients suffering from a variety of dermatoses or pruritis. The composition contains effective concentrations of relevant chemicals, while helping in avoiding components which causes allergenic, irritating, acne-causing, comedogenic, irritant dermatitis, photosensitivity, or allergic contact sensitization and yet is aesthetically pleasing. The antipruritic composition of the invention is oil-free, fragrance-free, lanolin-free and free of formaldehyde-releasing preservatives.

U.S.2015/0272957 discloses a topical anorectal composition including trimethyl siloxysilicate; at least one surfactant selected from the group consisting of sodium lauryl sulfate, alkyl- and alkoxy-dimethicone copolyol, polysorbate and a combination thereof; a non-polar volatile siloxane solvent; at least 15% (w/w) water, and a pharmaceutical agent selected from the group consisting of pramoxine, phenylephrine, hydrocortisone, salicylic acid, nitroglycerine, sildenafil, or their salts and combinations thereof, wherein the composition is sufficiently designed to dry within 60 seconds after application to the anorectal mucosa to form a dried composition, and wherein the dried composition forms: a flexible film, wherein the flexible film closely follows irregularities of the body surface as well as movement of the body surface, and a durable film, wherein the durable film does not crack or flake off and remains intact for more than 12 hours giving release of the pharmaceutical agent for an extended period of time.

Pramoxine HCI is a desirable anesthetic agent as compared with other anesthetics, such as lidocaine and benzocaine, because many people have allergies to these other anesthetics. Pramoxine HCI does not cause the same topical sensitivity as compared to these other anesthetics, it is effective at minimal concentrations, and has a duration of action longer than that of other anesthetics (see, for example, Fisher, A.F.; "The Safety of Pramoxine Hydrochloride When Used as a Topical (Surface) Anesthetic," Cutis, 62:122-123 (1998); Fisher, A. A.; "Allergic Reactions to Topical (Surface) Anesthetics with Reference to the Safety of Tronothane," Cutis, 25:584 (1980); and Schmidt, J.L., Blockus, L.E., Richards, R.K., "The Pharmacology of Pramoxine Hydrochloride: A New Topical Anesthetic," Anesth. Analg., 32:418 (1953)).

The combination of hydrocortisone acetate and pramoxine is used to treat minor pain, itching, swelling, and discomfort caused by hemorrhoids and other problems of the anal area (e.g., anal fissures, itching). In the composition, pramoxine is used as an anesthetic that works by temporarily numbing the area; on the other hand, hydrocortisone acetate is used as a corticosteroid that reduces redness, itching, and swelling.

While corticosteroids are highly effective in the treatment of the above systemic and local conditions, they suffer from one significant disadvantage. The size and shape of corticosteroids makes them exceedingly difficult to deliver percutaneously. Conventional and commercial topical steroid preparations are only marginally effective in delivering sufficient steroid for immediate treatment of local conditions; systemic steroid treatment by percutaneous delivery from known vehicles is virtually impossible. Accordingly, a vehicle system which increases both the level and speed of in-vitro release of the steroid through the skin would be more efficient in the treatment of localized conditions and, more importantly, would greatly increase the chances of making systemic treatment by topical application viable. Effective systemic delivery of steroids by the topical mode of treatment is highly desirable since the topical treatment would result in a lower level of side effects than those associated with conventional (oral or parenteral) methods of administration when systemic steroid therapies are indicated. Various studies exist regarding the formulation of steroids to provide an increase in in-vitro release over conventional steroid vehicles.

Unfortunately, due to its highly hydrophobic nature, hydrocortisone acetate is poorly absorbed through membranes such as the skin of mammals, including humans. Therefore, the success of transdermally administering therapeutically effective quantities of hydrocortisone acetate to a mammal in need of such treatment within a reasonable time frame and over a suitable surface area has been substantially limited. However, it has been found that the rate and extent of hydrocortisone acetate transdermal absorption can be improved by administering hydrocortisone acetate in compositions comprising penetration enhancers that improve absorption across the skin. Described herein are compositions comprising hydrocortisone acetate and pramoxine, including penetration enhancers that when transdermally administered to a mammal, such as a human, provide a therapeutic systemic concentration of hydrocortisone acetate and pramoxine. Also, described herein are formulations of topical compositions obtained at a specified pH range within comprising penetration enhancers and surfactants in a given ratio.

The present invention addresses the need to effectively treating conditions of topical applications which are local in nature systemically with the same treatment regimen. In this way, the present inventors have developed a cream formulation comprising hydrocortisone acetate and pramoxine having enhanced in-vitro release compared to the commercially available reference products.

Description of the Invention:

It is an object of the present invention to provide a novel topical formulation for enhancing the in-vitro release of hydrocortisone and pramoxine.

It is a further object of the present invention to provide such compositions which provide sufficient skin penetration enhancement to achieve therapeutic levels of the hydrocortisone acetate and pramoxine in target tissues.

The present invention relates to prevention or treatment of an anorectal disorder, achieving a better therapeutic effect than commercially available compositions comprising the same active ingredient(s) in the same concentrations.

The present invention relates to develop a pharmaceutical composition suitable for topical administration of hydrocortisone and pramoxine, or pharmaceutically acceptable salts, esters, hydrates and solvates thereof, which composition exhibits enhanced in- vitro release to human and animal tissue and improved stability upon long-term storage.

The present invention provides improved in-vitro release of topical composition comprising hydrocortisone acetate and pramoxine together with penetration agents.

Another object is to provide a cream formulation in which hydrocortisone acetate and pramoxine are well in-vitro released and does not substantially degrade during storage.

The present invention relates to a topical pharmaceutical composition containing oil and aqueous phases, having enhanced in-vitro release through the skin, comprising the following components:

(a) hydrocortisone and pramoxine active substances;

(b) at least one penetrating agent;

(c) at least one surfactant;

(d) at least one emollient/ emulsifying agent; (e) at least one antimicrobial preservative;

(f) at least one solvent; wherein the pH of the finished product is between 3 to 4.5, preferably between

3.5 to 4.5.

The present invention relates to a topical pharmaceutical composition containing oil and aqueous phases, having enhanced in-vitro release through the skin, comprising the following components:

(a) hydrocortisone and pramoxine active substances;

(b) at least one penetrating agent selected as isopropyl palmitate which is used in an amount of about 2.0% to 4.0% (w/w) of the composition;

(c) at least one surfactant selected as triethanolamine lauryl sulphate which is used in an amount of about 1 % (w/w) of the composition;

(d) at least one emollient/ emulsifying agent;

(e) at least one antimicrobial preservative;

(f) at least one solvent; wherein the pH of the finished product is between 3 to 4.5, preferably between

3.5 to 4.5.

The present invention relates to a topical pharmaceutical composition comprising:

(a) hydrocortisone acetate and pramoxine HCI active substances;

(b) isopropyl palmitate as a penetrating agent;

(c) triethanolamine lauryl sulphate as surfactant;

(d) stearic acid, polyoxyl 40 stearate, lanolin alcohol, liquid paraffin and cetyl alcohol as emollient/ emulsifying agent;

(e) potassium sorbate and sorbic acid as antimicrobial preservative;

(f) propylene glycol is as solvent (cosolvent); wherein the pH of the finished product is between 3 to 4.5, preferably between

3.5 to 4.5.

In some embodiments, the hydrocortisone compound is hydrocortisone acetate which is present in an amount of from about 0.5 to about 3.0 wt. % relative to the weight of total composition.

In some embodiments, the pramoxine compound is pramoxine hydrochloride which is present in an amount of from about 0.25 to about 1.5 wt. % relative to the weight of total composition. The present invention relates to a pharmaceutical composition of hydrocortisone acetate and pramoxine HCI having stearic acid between 5% to 10% (w/w) of the composition, preferably 8% to 9% (w/w) of the composition.

Pharmaceutical gel and cream formulations for topical delivery of drugs are well known. However, many such formulations are not suitable for certain applications due to problems with, for example, insolubility and/or degradation of the drug in the formulation, and physical instability of the formulation (separation of components, thickening, precipitation/agglomerization of active ingredients, and the like). In the present invention, the composition is cream dosage form having improved stability upon long-term storage.

Accordingly, the invented stable formulation which increases both the level and speed of in-vitro release of the hydrocortisone acetate and pramoxine through the skin would be more efficient in the treatment of localized conditions and, more importantly, would greatly increase the chances of making systemic treatment by topical application viable. Effective systemic delivery of corticosteroids by the topical mode of treatment is highly desirable since the topical treatment would result in a lower level of side effects than those associated with conventional (oral or parenteral) methods of administration when systemic steroid therapies are indicated.

Specifically, it has been discovered to provide enhanced in-vitro release of hydrocortisone acetate and pramoxine from the topical composition developed in the present formulation at a specified pH range within comprising penetration enhancers and surfactants in a given ratio.

The expression “comprising” means “including, but not limited to”. Thus, other nonmentioned substances, additives, carriers, or steps may be present.

As used herein the term 'topical formulation' refers to a formulation that may be applied to skin or a mucosa. Topical formulations may, for example, be used to confer therapeutic benefit to a patient or cosmetic benefits to a consumer. Topical formulations can be used for both topical and transdermal administration of substances.

The term 'topical administration' is used in its conventional sense to mean delivery of a substance, such as a therapeutically active agent, to the skin or a localized region of the body. Topical administration of a drug may often be advantageously applied in, for example, the treatment of various skin disorders. By "effective amount', as used herein, is meant sufficient amount of the composition(s) to provide the desired immunosuppresive or anti-inflammatory effect and performance at a reasonable benefit/risk ratio attendant any medical treatment. Within the scope of sound medical judgment, the amount of pharmaceutical actives used will vary with the particular condition being treated, the severity of the condition, the duration of the treatment, the specific compound employed, its concentration, the condition of the patient, concurrent therapies being administered, and like factors within the specific knowledge and expertise of the patient or the attending physician.

As used herein, “stable” refers to a composition that substantially maintains its physical and chemical properties when stored. Especially, appearance, identification, content uniformity, pH, viscosity, assay, related compounds, microbiological tests and in-vitro release testing results of the composition should not be extremely changed after production (To, initially) and during the storage conditons throughout the shelf life.

The pharmaceutical compositions described herein can, if desired, include one or more pharmaceutically acceptable excipients. The term "excipient" herein means any substance, not itself a therapeutic agent, which may be used as a carrier or vehicle for delivery of a therapeutic agent to a subject or combined with a therapeutic agent (e.g., to create a pharmaceutical composition) to improve its handling or storage properties or to permit or facilitate formation of a dose unit of the composition. Excipients include, by way of illustration and not limitation, binders, disintegrants, taste enhancers, solvents, thickening or gelling agents (and any neutralizing agents, if necessary), penetration enhancers, solubilizing agents, wetting agents, antioxidants, lubricants, emollients, emulsifying agents, surfactants, substances added to mask or counteract a disagreeable odor, fragrances or taste, and substances added to improve appearance or texture of the composition. Any such excipients can be used in any dosage forms according to the present disclosure. The foregoing classes of excipients are not meant to be exhaustive but merely illustrative as a person of ordinary skill in the art would recognize that additional types and combinations of excipients could be used to achieve the desired goals for delivery of hydrocortisone acetate and pramoxine from the topical composition.

The term 'penetration enhancer' is used herein to refer to an agent that improves the transport of molecules such as an active agent (e.g., a medicine) into or through the skin. Various conditions may occur at different sites in the body either in the skin or below creating a need to target delivery of compounds. For example, in products designed to produce artificial tans delivery of dye substances into the stratum corneum may be advantageous. A psoriasis treatment on the other hand may require delivery of therapeutic drug levels in deeper epidermal tissue. In a treatment for osteoarthritis delivery of the active agent into deeper underlying joint tissue may be necessary to achieve therapeutic benefit. In yet other applications, for example in hormone replacement therapy, delivery of drug to the systemic circulation may be an objective. Thus, a 'penetration enhancer' may be used to assist in the delivery of an active agent directly to the skin or underlying tissue or indirectly to the site of the disease through systemic distribution. A penetration enhancer may be a pure substance or may comprise a mixture of different chemical entities.

The penetration enhancer is present in an amount sufficient to enhance the penetration of the hydrocortisone acetate and pramoxine. The specific amount varies necessarily according to the desired release rate and hydrocortisone acetate and pramoxine active ingredients used. Generally, this amount ranges from about 0.5 percent to about 10 percent, based on the total weight of the composition. Preferably, the penetration enhancer is about 1.5 to 5 weight percent of the composition. In the present invention, the penetration enhancer is about 2.0% to 4.0% (w/w) of the composition.

In one embodiment, the hydrocortisone acetate and pramoxine can be combined with at least one penetration enhancing agent for transdermal or topical delivery. A penetration enhancer is an excipient that aids in the delivery of an active agent into and/or through the stratum corneum. Penetration enhancers are also known as accelerants, adjuvants or sorption promoters. A suitable penetration enhancer for use in the compositions and methods described herein would preferably exhibit one or more of the following qualities: (i) highly potent, with a specific mechanism of action; (ii) exhibit a rapid onset upon administration; (iii) have a predictable duration of action; (iv) have only non-permanent or reversible effects on the skin; (v) chemically stable; (vi) have no or minimal pharmacological effects; (vii) be physically and chemically compatible with other formulation components; (viii) be odorless; (ix) be colorless; (x) be hypoallergenic; (xi) be non-irritating; (xii) be non-phototoxic; (xiii) be non- comedogenic; (xiv) have a solubility parameter ■ approximating that of the skin (10.5 cal/cm); (xv) be readily available; (xvi) inexpensive; and (xvii) be able to formulated into pharmaceutical compositions for topical or transdermal delivery of an active pharmaceutical agent.

In this present invention, isopropyl palmitate was selected as penetration agent. Isopropyl palmitate is a clear, colorless or pale yellow, odorless, viscous liquid that solidifies below 16°C and is soluble in acetone, chloroform, ethanol, ethylacetate, mineral oil, and insoluble in glycerin, glycol and water. It is generally used as a skin penetration enhancer in pharmaceutical formulations.

In one embodiment, the compositions described herein comprise a surfactant. Triethanolamine lauryl sulphate is a pale yellow-yellow colored viscous liquid and is used as a surface active agent in topical pharmaceutical preparations. It is used in an amount of about 1% (w/w) of the composition.

In the present invention, propylene glycol was used as a solvent (cosolvent). Propylene glycol is a clear, colorless, practically odorless viscous liquid, miscible with acetone, chloroform, ethanol, glycerine and water. It is used as an antimicrobial preservative, humectant and co-solvent in topical pharmaceutical preparations. It is a better general solvent than glycerin and dissolves a wide variety of materials, such as corticosteroids, phenols, sulfa drugs, barbiturates, vitamins (A and D), most alkaloids, and many local anesthetics. In particular, propylene glycol has been described in several articles in the literature as enhancing the penetration of certain pharmacologically active agents, such as the corticosteroids.

In one embodiment, the compositions described herein comprise an antimicrobial preservative. Illustrative anti-microbial preservatives include acids, including but not limited to benzoic acid, phenolic acid, sorbic acids, alcohols, benzethonium chloride, bronopol, butylparaben, cetrimide, chlorhexidine, chlorobutanol, chlorocresol, cresol, ethylparaben, imidurea, methylparaben, phenol, phenoxyethanol, phenylethyl alcohol, phenylmercuric acetate, phenylmercuric borate, phenylmercuric nitrate, potassium sorbate, propylparaben, sodium propionate, or thimerosal. In the present invention, a combination of potassium sorbate and sorbic acid were selected as antimicrobial preservative. Potassium sorbate is in the form of white crystalline powder and has a characteristic odor. It is generally used as an antimicrobial preservative in topical pharmaceutical preparations. Sorbic acid is a white-yellowish crystalline powder and has a characteristic odour. It is generally used as an antimicrobial preservative in topical pharmaceutical preparations.

An optional, but preferred, component of the present invention is an emulsifier. Although not a critical factor, a suitable emulsifier generally will exhibit a hydrophilic- lipophilic balance. In one embodiment, the compositions described herein comprise emullien & emulsifying agent. The term "emulsifying agent" or "emulsifier" is used throughout the specification to describe a compound which is added to certain compositions according to the present invention in order to harmonize water to produce oil-in-water (lotions) and water-in-oil (creams) emulsions according to the present invention. Emulsifiers as used generally are considered surfactants which exhibit good surface activity and produce a low interfacial tension in the system in which it is used. Mixtures of emulsifiers also may be preferred, especially where one of the emulsifiers is preferentially oil-soluble and at least one of the emulsifiers is preferentially water- soluble (or dispersible). One of ordinary skill in the art may readily determine the type and amount of emulsifier or emulsifying system (group of emulsifiers) which may be used in the compositions according to the present invention which include water. Exemplary emulsifiers for use in the present invention may be non-ionic, anionic, cationic or amphoteric emulsifiers. In the present invention, stearic acid, polyoxyl 40 stearate, lanolin alcohol, liquid paraffin and cetyl alcohol were selected as emollient/ emulsifying agent. Stearic acid is a white or slightly yellow bright, crystalline or yellowish white powder, soluble in benzene, ether, soluble in ethanol, propylene glycol, hexane, and practically insoluble in water. It is generally used as an emulsifier in topical pharmaceutical preparations. Cetyl alcohol is a white or cream colored, flake or granular substance with a slight characteristic odor. It melts with heat and turns into a colorless or yellow suspension. It is generally used as an emollient emulsifying agent in topical pharmaceutical preparations. Polyoxyl 40 stearate is a waxy solid, oily odor and water-soluble excipient. It is generally used as an emulsifier in topical pharmaceutical preparations. Lanolin alcohol is a pale yellow or golden brown solid with a characteristic odour. It is freely soluble in chloroform, dichloromethane, ether and liquid paraffin and practically insoluble in water. It is generally used as an emulsifier in topical pharmaceutical preparations. Liquid paraffin is a transparent, colorless, odorless and tasteless oily substance. It has a slight odor when heated. It is generally used as emollient in pharmaceutical formulations.

White vaseline is a substance that is a purified mixture of solid saturated hydrocarbons. It has a light yellowish color, transparent, soft and oily texture. It is tasteless and odorless. It is generally used as an oil phase carrier in pharmaceutical formulations.

Deionized water is used as a solvent and as a carrier for the aqueous phase.

As used herein, all percentages are by weight of total composition and all measurements are at 25°C, unless otherwise specified.

The following examples further describe and demonstrate embodiments within the scope of the present invention. The examples are given solely for the purpose of illustration and are not to be construed as limitations of the present invention, as many variations thereof are possible without departing from the spirit and scope of the invention.

EXAMPLES Example 1. Preparation of Cream Formulation

At the beginning of product development studies; PDR and literature, drug master file (DMF) of the active substance were used for the selection of excipients. In addition, the properties of the finished product were determined by taking into account the content, pH and viscosity of the formulation of the reference product. In a preferred embodiment of the invention, the pharmaceutical composition of the present invention has the following composition:

Table 1 : Composition of the product

Ingredients Function

Hydrocortisone acetate Active substance

Pramoxine HCI Active substance

Stearic acid Emulsifying agent

Cetyl alcohol Emollient/ Emulsifying agent

White vaseline Oil phase carrier

Isopropyl palmitate Penetration agent

Polyoxyl 40 stearate Emulsifying agent

Propylene glycol Solvent (cosolvent)

Potassium sorbate Antimicrobial preservative

Sorbic acid Antimicrobial preservative

Liquid paraffin Emollient

Lanoline alcohol Emulsifying agent

Trietanolamin lauryl sulphate Surfactant

Deionized water Aqueous phase carrier

The production method of cream and ointment in pharmaceutical technology is based on the preparation and mixing of two different phases; oil phase and aqueous (water) phase, separately. An oil/water emulsion was prepared by mixing the phases. Since it was desired to obtain a smooth cream, the prepared cream was smoothed with a homogenizer. Finally, the pH was measured; if it was within about 3.0 to 4.5, preferably between 3.5 to 4.5, the batch was complete. The critical parameters of the production process were determined as the addition of active substances and excipients to the optimal phase, mixing speed and time, temperature and homogenization speed.

Example 2. Control Tests For pharmaceutical products, the typical semisolid dosage form quality control tests include appearance, identification, content uniformity, pH, viscosity, assay, related compounds, microbiological tests and in-vitro release testing. Similar to the dissolution testing of oral dosage forms, a simple, reliable and reproducible in-vitro release rate method can guide formulation development; help to monitor batch-to-batch quality and stability, and control the manufacturing process of cosmeceuticals. It is particularly useful for detecting the effect of product changes including drug substance, excipients, and manufacturing process.

Table 2. Results of control tests

Tests Results

Appearance White, smooth semi-solid cream

Identification The retention time of the active substance main peaks in the chromatogram of the sample solution is consistent with the chromatogram of the standard solution obtained from the quantification.

Content Uniformity

Hydrocortisone acetate 100.6% & RSD 0.71 %

Pramoxine HCI 100.8% & RSD 0.78% pH 3.85

Viscosity (cp) 268 e ³

Assay

Hydrocortisone acetate 100.6%

Pramoxine HCI 100.8%

Antimicrobial preservative 102.1%

Related Compounds

Maximum degradation product 0.19%

Total Impurity 0.20%

Microbiological Tests

Total Aerobic Microbial Count <10 ²

Total Mold/Yeast Count <10

Escherichia coli /g Not found

Staphylococcus aureus Not found

Pseudomonas aeruginosa Not found

Example 2: In Vitro Release Testing For a topical medicament to be effective it must be readily released from the vehicle matrix and interact intimately with the skin to be treated. On this basis candidate compositions can be ranked based on in-vitro release rates through artificial or post mortem skin membranes. This is routinely undertaken using the Franz Diffusion Cell methodology. The rate and extent to which the drug substance is released from the product matrix are particularly relevant to the prediction of relative efficacy of candidate formulations.

In Vitro Release Testing (I RT) is a useful test to assess product similarity under certain scale and post approval changes for semisolid products. The FDA Guidance on Scale up and Post Approval Changes for Semisolid (SUPAC-SS) describes suitable conditions for this testing.

A number of formulations are shown in Table 3 below to illustrate the effect of changes in components on the release of the hydrocortisone acetate and pramoxine HCI active ingredients (The amount of other excipients was fixed in all formulas). Table 3. Compositions for the different formulations

„ Ratio %

Ingredients

FT-1 FT-2 FT-3

Hydrocortisone acetate 2.5 2.5 2.5

Pramoxin HCI 1 1 1

Stearic acid 9 9 8

White vaseline 12 12 5

Isopropyl palmitate 2 2 4

Cetyl alcohol ~

Polyoxyl 40 stearate ~

Propylene glycol ~

Potassium sorbate ~

Sorbic acid ~

Liquid paraffin ~

Lanoline alcohol 0 1 1

Trietanolamin lauryl sulphate 1 1 1

Deionized water q.s. q.s. q.s.

*Some excipient amounts were kept constant in all formulas and indicated by the symbol

A number of formulations comprising hydrocortisone acetate and pramoxine were tested for in-vitro release through Strat-M membrane using Franz diffusion cells in comparison to the reference product (Pramosone Cream %2,5). First described by Franz dissolution apparatus (1978), this cell has a small donor compartment and a cylindrical receptor chamber that allows mixing with a magnetic stir-bar as shown in the Figure 1. The apparatus used for IVRT is a Franz diffusion cell system. A Franz Diffusion Cell consists of two compartments, a donor and a receiver compartment. It consists of six individual cells. Each cell has a standard open cap ground glass surface with 15 mm diameter orifices, 35 mL volume capacity, and total diameter of 25 mm. The upper and lower portions are held together by means of a clamp. The portion of the cell below the mounted membrane is completely filled with receptor fluid (pH 7.4 & 0.1 M potassium phosphate buffer : ethanol) of 70:30 ratio such that the receptor fluid is in contact with the membrane. The receptor fluid is stirred by means of magnetic stirrer. About 400 mg of the semisolid preparation is placed uniformly on a synthetic membrane and kept occluded to prevent solvent evaporation and compositional changes. Multiple sampling times (at least 5 times) over an appropriate time period are suggested in order to generate an adequate release profile and to determine the drug release rate. Each aliquot removed is then typically analyzed, for example, by high performance liquid chromatography (i.e., HPLC). After each aliquot was removed, the cell was refilled with a volume of fresh medium equal to the volume of the aliquot that was removed. Results are reported as the cumulative amount of drug released at 30, 60, 120, 180, 240 and 300 minutes and are expressed in units of mg/cm ² .

The conditions used for IVRT for the example compositions of the invention are as follows:

Receptor medium pH 7.4 Buffer : Ethanol (70:30)

Speed 500 rpm

Strat-M membrane filter

Membrane (Merck Millipore)

Sample application ~ 400 mg

Temperature 32°C ± 0.5°C

Sampling times 0.5, 1 , 2, 3, 4, 5 hours

(6 points)

*pH 7.4 Buffer Preparation: 13.6 g of potassium dihydrogen phosphate is dissolved in 1 liter of water; the pH value is adjusted to 7.4 with 10 N NaOH.

The concentration of hydrocortisone acetate and pramoxine in the samples were measured using HPLC analysis. Specifically, HPLC was carried out with CDS 3V column (250 x 4.6 mm, 5pm) and using pH 7.5 phosphoric acid buffer : acetonitrile (40:60) as the mobile phase. Flux rates were calculated using standard equations based on the total transference of hydrocortisone acetate and pramoxine across the skin after 5 hours. Thus, flux rates, F, were computed according to wherein: D is the concentration of the active substances in the receptor well after incubation time t, V is the volume of the receptor well and A is the surface area of membrane. The in vitro penetration rate profiles were given at Figure 2 and Figure 3. According to in vitro release profiles, the inventive formulations were more effective at enhancing hydrocortisone acetate and pramoxine in-vitro release through the skin when compared to commercially available reference product. Considering the analgesic property of the active substance of pramoxine, its rapid and high in-vitro release provides rapid relief of pain for the patient. This was evaluated as the surprised and technical effect of the developed product.

FIGURES:

Figure 1. Schematic representations of Franz dissolution apparatus Figure 2. In vitro release profile for hydrocortisone acetate in comparison with reference product (Pramosone Cream %2,5)

Figure 3. In vitro release profile for pramoxine HCI in comparison with reference product (Pramosone Cream %2,5)