Preservative system for topically administrable pharmaceutical compositions containing a fatty acid/amino acid soap

[0002] This application claims priority from co-pending U.S. provisional application, Ser. No. 60/105,819, filed Oct. 27, 1998.

[0003] The present invention relates generally to the preservation of pharmaceutical compositions. In particular, the present invention relates to the use of certain fatty acid/amino acid soaps in combination with an antifungal acid and a chelating agent as a preservative system for topically administrable pharmaceutical compositions.

[0004] Multi-dose pharmaceutical products, particularly those intended for topical administration to the eyes, nose or ears, often contain or are required to contain a preservative. Such products are sterilized when manufactured, but contain preservatives to prevent or inhibit microbial growth in the event they are contaminated during use. The most common preservatives for topical, multi-dose ophthalmic products are quaternary ammonium preservatives, such as benzalkonium chloride and polyquaternium-1. Other known preservatives for topical, multi-dose ophthalmic products are chlorobutanol; chlorhexidine; parabens; and thimerosal (though thimerosal is not as common as it used to be, due to regulatory and environmental concerns related to the fact it contains mercury).

[0005] In some instances, preservatives alone are insufficient to meet regulatory standards for preservative efficacy. In such cases, preservative aids or adjuncts are used. Examples of preservative enhancing additives include EDTA (edetate disodium) and boric acid. Additional examples of preservative enhancing additives include certain sarcosinate and lactylate surfactants.

[0006] U.S. Pat. No. 5,520,920 (Castillo, et al.) discloses the use of certain modified sarcosinates and lactylates to enhance antimicrobial effectiveness of ophthalmic compositions, particularly in the case where cationic preservatives otherwise bind to anionic polyelectrolytes. Representative modified sarcosinates include those sold under the Hamposyl® trade name, such as lauroyl sarcosine (Hamposyl® L), oleoyl sarcosine (Hamposyl ® O), myrstoyl sarcosine (Hamposyl® M), cocoyl sarcosine (Hamposyl® C), stearoyl sarcosine (Hamposyl® S), and pelargodoyl sarcosine (Hamposyl® P). Representative lactylates include sodium capryl lactylate (Pationic® 122A).

[0007] Fatty acid/amino acid soaps are known and include, for example, those surfactants sold under the Aminosoap® trade name (Ajinomoto Co., Inc., Tokyo, Japan). According to product brochures, Aminosoap® surfactants are used in hair and body care (hair shampoo, body wash and bath foam), facial care (facial cleanser, facial washing foam, facial washing crbme, and make-up remover), and household and health care.

[0008] Alternative preservative systems for topically administrable pharmaceutical compositions are desired, especially in those instances when conventional preservatives, such as benzalkonium chloride, are incompatible with other ingredients in the composition.

[0009] The present invention provides a preservative system for topically administrable pharmaceutical compositions. The preservative system consists essentially of one or more fatty acid/amino acid soaps, one or more pharmaceutically acceptable antifungal acids and one or more pharmaceutically acceptable chelating agents. According to the present invention, topically administrable pharmaceutical compositions are preserved without the need for a conventional preservative ingredient. Thus, the compositions of the present invention do not contain any preservatives selected from the group consisting of quaternary ammonium preservatives, such as benzalkonium chloride, benzalkonium bromide, and polyquaternium-1; chlorhexidine; chlorobutanol; cetylpyridinium chloride; parabens; and thimerosal.

[0010] The present invention also relates to a method of preserving a topically administrable pharmaceutical composition, wherein the method comprises adding the preservative system described above to such composition.

[0011] Among other factors, the present invention is based on the finding that topically administrable pharmaceutical compositions can be preserved using a preservative system consisting of one or more fatty acid/amino acid soaps, one or more pharmaceutically acceptable antifungal acids and one or more pharmaceutically acceptable chelating agents, without the need for a conventional preservative ingredient.

[0012] Unless indicated otherwise, all amounts of composition ingredients expressed in percentage terms are expressed as weight/weight.

[0013] Fatty acid/amino acid soaps useful in the preservative systems of the present invention are those wherein the fatty acid component is derived from a C₈-C₂₄fatty acid and the amino acid component is selected from the group consisting of lysine and arginine. Preferably, the fatty acid component is selected from the group consisting of cocoyl, linoleoyl, lauroyl, myristoyl, stearoyl, oleoyl, and pelargodoyl fatty acid residues. Such fatty acid/amino acid soaps are commercially available or can be made by known methods. For example, the soap where the fatty acid component is cocoyl and the amino acid component is derived from arginine is commercially available as AMINOSOAP AR-12 from Ajinomoto Co., Inc. (Tokyo, Japan). The soap where the fatty acid component is cocoyl and the amino acid component is derived from lysine is available as AMINOSOAP LYC-12.

[0014] In general, the amount of fatty acid/amino acid soap present in the compositions of the present invention is from about 0.001 to about 1%, preferably from about 0.01 to about 0.2%, and most preferably from about 0.03 to about 0.12%. For topical ophthalmic preparations, the concentration of the fatty acid/amino acid soap should not be so high that it causes severe discomfort.

[0015] The preservative systems of the present invention also contain one or more pharmaceutically acceptable antifungal acids selected from the group consisting of boric acid; benzoic acid; salicylic acid; sorbic acid; lactic acid; acetic acid; and pharmaceutically acceptable salts thereof. Boric acid is the most preferred antifungal acid. In general, the amount of antifungal acid present in the compositions of the present invention is from about 0.01 to about 1%, preferably about 0.1 to about 0.6%, and most preferably from about 0.3 to about 0.4%. The antifungal acid component can be added to pharmaceutical compositions in the form of a pharmaceutically acceptable salt.

[0016] In addition to the fatty acid/amino acid soap(s) and antifungal acid(s), the preservative system contains one or more pharmaceutically acceptable chelating agents. Such chelating agents are selected from the group_consisting of EDTA; ethylene glycol-bis-(b-aminoehtylether) N,N,N′,N′-tetraacetic acid (EGTA); 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA); ethylene-N,N′-diglycine (EDDA); 2,2′-(ethylendiimino)-dibutyric acid (EDBA); and pharmaceutically acceptable salts thereof. The most preferred chelating agent is EDTA. The chelating agents can be added to pharmaceutical compositions in the form of a pharmaceutically acceptable salt. For example, EDTA may be added in the form of edetate disodium. In general, the amount of chelating agent present in the compositions of the present invention is from about 0.001 to about 1%, preferably about 0.01 to about 0.2%, and most preferably about 0.01 to about 0.1%.

[0017] The preservative system of the present invention can be used in all types of topically administrable pharmaceutical compositions (e.g., solutions, suspensions, emulsions, gels), but is preferably used for topically administrable ophthalmic, otic, nasal or dermal compositions. Most preferred are topically administrable ophthalmic or otic compositions.

[0018] The topically administrable pharmaceutical compositions of the present invention optionally comprise, in addition to the preservative system described above, conventional ingredients, provided that the compositions do not contain a conventional preservative. For example, the compositions of the present invention may contain one or more active ingredients (though, in some instances, such as in the case of dry eye products, no drug will be present). Other optional ingredients include, but are not limited to, pharmaceutically acceptable buffers, tonicity agents, drug carriers, sustained-release agents, viscosity modifying agents, comfort-enhancing agents, solubilizing aids, pH adjusting agents, antioxidants and other stabilizing agents.

[0019] The active ingredient or ingredients that can be included in the compositions of the present invention include all ophthalmic, dermatological, otic or nasal agents that can be topically applied. For example, such ophthalmic agents include (but are not limited to): anti-glaucoma agents, such as beta-blockers (e.g., betaxolol and timolol), muscarinics (e.g., pilocarpine), prostaglandins, carbonic anhydrase inhibitors (e.g., acetazolamide, methazolamide and ethoxzolamide), dopaminergic agonists and antagonists, and alpha adrenergic receptor agonists, such as para-amino clonidine (also known as apraclonidine) and brimonidine; anti-infectives, such as ciprofloxacin; non-steroidal and steroidal anti-inflammatories, such as suprofen, ketorolac, dexamethasone, rimexolone and tetrahydrocortisol; proteins; growth factors, such as EGF; and anti-allergic agents, such as cromolyn sodium, emedastine and olopatadine. Compositions of the present invention may also include combinations of active ingredients.

[0020] Sustained release agents include anionic polyelectrolytes, such as high molecular weight (e.g., 50,000-6,000,000), anionic mucomimetic polymers (e.g., carboxyvinyl polymers, such as Carbopol®, and xanthan gum), polystyrene sulfonic acid polymers, cationic exchange resins (e.g., Amberlite® or Dowex®), and the like.

[0021] The following examples are presented to illustrate further various aspects of the present invention, but are not intended to limit the scope of the invention in any respect.

[0022] Preparation

[0023] 0.28g betaxolol hydrochloride and 0.250 grams of amberlite IRP 69 were stirred in ˜25 mL of water for ˜15 minutes. To this suspension were added 22.5g 2% stock slurry of Carbomer 974P, 0.40 g boric acid, 4.15 g mannitol, and 0.01 g disodium EDTA. The pH of the mixture was adjusted to ˜6.0 by the addition of 11 mL of 10% tromethamine solution followed by 30 minutes of stirring. 0.15 g Aminosoap LYC-12 (30% cocoyl N-lysine) was then added. Finally, pH is readjusted to 6.5 with 10% tromethamine and the formulation was brought to 100 g by the addition of purified water.

[0024] Antimicrobial preservative effectiveness was determined using an organism challenge test according to the methods described in the United States Pharmacopeia (USP) and European Pharmacopoeia (Ph.Eur.). Samples were inoculated with known levels of one or more of the following: gram-positive (Staphylococcus aureusATCC 6538) and gram-negative (Pseudomonas aeruginosaATCC 9027 and Escherichia coliATCC 8739) vegetative bacteria, yeast (Candida albicansATCC 10231) and mold (Aspergillus nigerATCC 10 16404). The samples were then pulled at specified intervals to determine if the antimicrobial preservative system was capable of killing or inhibiting the propagation of organisms purposely introduced into the formulation. The rate or level of antimicrobial activity determines compliance with the USP and/or Ph.Eur. preservative efficacy standards for ophthalmic preparations.

[0025] The compendial preservative standards for ophthalmic preparations are presented below:

[0026] For Bacteria

[0027] For Fungi

[0028] The results of the microorganism challenge tests are shown in Tables 1 and 2 below.

[0029] The invention in its broader aspects is not limited to the specific details shown and described above. Departures may be made from such details within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its advantages.