Abstract:
A steroid cream formulation which has enhanced physical and chemical stability is formed of (11β,17α)-17-(ethylthio)-9α-fluoro-11β-hydroxy-17-(methylthio)androsta-1,4-dien-3-one (tipredane), and a vehicle containing as major ingredients propylene glycol and water together with a sodium citrate or potassium citrate buffer to impart an acid value to the cream formulation of greater than 3, a high melting point wax, such as white wax, to impart proper consistency without adversely affecting stability of the tipredane, benzyl alcohol as a preservative, together with one or more emulsifiers, which include glyceryl stearate, one or more emollients which include isopropyl isostearate or isopropyl palmitate, lubricants and other conventional cream formulation ingredients.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a steroid cream formulation which has enhanced physical and chemical stability and contains (11β, 17α)-17-(ethylthio)-9α-fluoro-11B-hydroxy-17-(methylthio)androsta-1,4-dien-3-one (tipredane) as an active ingredient. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 4,361,559 to Varma discloses antiinflammatory 17,17-bis(substituted thio)androstenes of the formula ##STR1## wherein R 1  and R 2  are the same or different and each is alkyl, cycloalkyl or aryl; 
     R 3  is hydrogen, hydroxy, alkoxy, aryloxy, alkylthio, arylthio, ##STR2##  or halogen; R 4  is hydrogen, methyl, hydroxy, ##STR3##  or halogen; R 5  is hydrogen or halogen; and 
     R 6  is carbonyl or B-hydroxymethylene. A broken line in the 1,2-,6,7- and 15,16-position of a structural formula indicates the optional presence of ethylenic unsaturation. 
     Includes among the compounds covered in the Varma patent is tipredane which has been found to be a highly effective topical antiinflammatory agent. 
     Tipredane is practically insoluble in water (less than 0.0002 mg/ml at 25° C.); 1:1 hydroalcoholic mixtures of tipredane are stable at pH 6.5-8.0 and unstable under acidic conditions while tipredane itself is susceptible to oxidation. 
     It is known to use monoglycerides such as glyceryl monostearate as a thickener in steroid cream formulations. For example, U.S. Patent No. 3,892,857 to DiFazio et al discloses a cream formulation containing propylene glycol, water and a steroid, namely, 21-chloro-9α-fluoro-Δ 4  -pregnene-11β, 16α, 17α-triol-3,20-dione 16,17-acetonide (halcinonide) and as an oleaginous thickener monoglycerides such as glyceryl monostearate, glyceryl monooleate, glyceryl monopalmitate and glyceryl ricinoleate. 
     Where it has been attempted to employ generally commercially available glyceryl monostearate in an oil-in-water tipredane cream formulation, it has been found that syneresis of the aqueous phase occurs with some lots of glycyl monostearate. 
     U.S. application Ser. No. 120,278, filed Nov. 13, 1987, assigned to E. R. Squibb &amp; Sons, Inc., which will issue as U.S. Pat. No. 4,868,169 on Sept. 9, 1989, discloses a tipredane cream formulation which includes tipredane, water, an emulsifier which includes glyceryl monostearate, a buffer, a non-acid long chain fatty acid wax, optionally one or more emollients, optionally one or more chelating agents, optionally one or more lubricants, optionally one or more antioxidants, and optionally one or more skin conditioners. 
     DESCRIPTION OF THE INVENTION 
     In accordance with the present invention, a soft, non-greasy, cosmetically elegant topical oil-in-water steroid cream formulation is provided which contains the steroid tipredane as its active ingredient alone or in combination with an antifungal agent and has excellent physical and chemical stability and does not undergo any significant syneresis or bleeding although it contains glyceryl monostearate from any source including commercially available sources heretofore known to cause synerises in tipredane creams. The oil-in-water cream formulation according to the present invention contains in addition to tipredane alone or in combination with an antifungal agent, a carrier vehicle which is formed of one or more solubilizers for the tipredane, water, one or more emulsifiers including glyceryl monostearate, one or more buffers, isopropyl isostearate and/or isopropyl palmitate as an emollient, benzyl alcohol and/or other preservative, optionally one or more other emollients, optionally one or more metal chelating agents, optionally one or more skin conditioners, and optionally one or more silicone lubricants or defoaming agents. 
     In addition, in order to obtain acceptable consistency and chemical stability, the cream formulation of the invention will include a high melting point wax having a melting point above about 60° C. such as white wax (also referred to as beeswax). It has been found that such wax will impart the desired heat storage stability to the cream but will not interfere with the stability of the tipredane. In addition or in place of white wax, the cream formulation may also include a synthetic beeswax (for example Synchrowax), microcrystalline wax, carnauba wax and the like. 
     The tipredane steroid will be employed in the form of a micronized powder having an average particle size of within the range of from about 2 to about 10 microns and will be present in an amount within the range of from about 0.005 to about 0.5% by weight and preferably from about 0.05 to about 0.3% by weight based on the total weight of the tipredane cream formulation. 
     As indicated, the carrier vehicle will contain one or more solubilizers for the tipredane such as propylene glycol which also serves as a preservative, propylene carbonate, polyethylene glycols or dimethylisosorbide or mixtures thereof. 
     The propylene glycol and/or other solubilizers will be present in an amount within the range of from about 5 to about 30% by weight and preferably from about 10 to about 20% by weight of the cream formulation. 
     Water which also serves as a solubilizer for a portion of the tipredane will be present in an amount within the range of from about 30 to about 65% and preferably from about 40 to about 60% by weight of the total cream formulation. 
     An important feature of the cream formulation of the invention is its excellent chemical stability and physical stability so that syneresis or bleeding will not occur even if glyceryl monostearate is present. 
     The cream formulation will include a thickener, a high melting point wax (melting point above about 60° C.) which is a white wax and/or other wax such as microcrystalline wax, synthetic beeswax, carnauba wax and the like, in an amount within the range of from about 1 to about 10 weight % and preferably from about 2 to about 5 weight % based on the weight of total tipredane cream formulation. 
     The emulsifier will be present in an amount within the range of from about 5 to about 25 weight % and preferably from about 8 to about 20 weight % based on the weight of the total tipredane cream formulation. Examples of emulsifiers suitable for use herein include but are not limited to glyceryl monostearate, cetyl alcohol, polyethylene glycol 60 sorbitan monolaurate (polysorbate 60), wool alcohols, polyethylene glycol 300 stearate and the like. It is preferred to employ a mixture of such emulsifiers, namely, glyceryl monostearate in an amount of within the range of from about 4 to about 12% by weight and preferably from about 5 to about 9% by weight, cetyl alcohol in an amount within the range of from about 2 to about 10% by weight and preferably from about 4 to about 6% by weight, and polysorbate 60 in an amount within the range of from about 2 to about 8% by weight, and preferably from about 3 to about 6% by weight, all of such % being based on the total weight of the tipredane cream formulation. 
     The emollients may be present in an amount within the range of from about 0.1 to about 10% and preferably from about 1 to about 5% by weight based on the total tipredane cream formulation. Examples of emollients suitable for use herein include but are not limited to a isopropyl isostearate, isopropyl palmitate, isopropyl myristate, ethylhexyl palmitate and the like. 
     The cream formulation may optionally include one or more skin conditioners in an amount of within the range of from about 0.1 to about 5% and preferably from about 0.5 to about 3% by weight based on the total tipredane cream formulation, such as an alkoxylated methyl glucose derivative, for example, polypropylene glycol-20 methyl glucose ether (Glucam E-20, trademark of Amerchol Corp, CPC Int.), polypropylene glycol-10 methyl glucose ether (Glucam P-10, trademark of Amerchol Corp, CPC Int.) and polyethylene glycol (10 or 20) ether of methyl glucose. Other skin conditioners that may be employed include allantoin, d- or dl-panthenol, sodium 2-pyrrolidone carboxylic acid and the like. 
     In addition, the cream formulation will include a silicone lubricant or defoamer in an amount within the range of from about 0.1 to about 2.5% by weight and preferably from about 0.5 to about 1.5% by weight based on the total tipredane cream formulation. Examples of silicone lubricants suitable for use herein include, but are not limited to Dimethicone 350 (Silicone DC 200 Fluid (350 CS)) or Dimethicone 200. 
     The cream formulation of the invention will include an antioxidant, such as sodium metabisulfite, butylated hydroxytoluene, acetone sodium bisulfite or sodium formaldehyde sulfoxylate in an amount within the range of from about 0.001 to about 0.1% by weight and preferably from about 0.005 to about 0.05% by weight of the tipredane cream formulation. Sodium metabisulfite is preferred. 
     As the optional metal chelating agent, (or anti-oxidant) disodium or dipotassium ethylene-diamine tetraacetate dihydrate is preferred. Other examples of metal chelating agents which may be employed include citric acid, phosphoric acid or monoisopropyl citrate. The metal chelating will be employed in an amount within the range of from about 0.001 to about 0.01% by weight and preferably from about 0.002 to about 0.008% by weight of the tipredane cream formulation. 
     In addition to tipredane, the cream formulation of the invention may include an antifungal agent in an amount within the range of from about 1 to about 25% and preferably from about 5 to about 20% by weight of the formulation. Examples of antifungal agents suitable for use herein include, but are not limited to, amphotericin B, nystatin, griseofulvin, miconazole, ketoconazole, tioconazole, econazole, clotrimazole and/or other macrolide antifungal agents. 
     The following represents preferred oil-in-water cream formulations in accordance with the present invention. 
     
         ______________________________________Ingredient           % by weight______________________________________Tipredane (in form of micronized                0.05    to     0.3powder)Antifungal agent (such as tioconazole)                0       to     5Glyceryl monostearate (emulsifier)                5       to     9Propylene glycol (solubilizer-                10      to     20preservative)Sodium citrate monohydrate (buffer)                0.4     to     0.5Benzyl alcohol (preservative)                0.8     to     1.5Disodium EDTA dihydrate (metal                0.002   to     0.008chelating agent)Aluminum hydroxide (buffer)                0.2     to     0.6White wax (thickener)                2       to     5Cetyl alcohol (emulsifier)                4       to     6Isopropyl isostearate (or                1       to     5isopropyl palmitate)Polysorbate 60 (emulsifer)                3       to     6Silicone fluid (defoamer)                0.2     to     2Water                        to     100%.______________________________________ 
    
     The tipredane cream formulation of the invention may be prepared as described in the working Examples as follows. All components except actives, propylene glycol and benzyl alcohol (if present) are heated and melted at 80 to 85° C. and homogenized for 10 to 30 minutes. The mix is cooled to 50° to 55° C., for example, by air-drying. 
     The actives, for example, tipredane alone or with, for example, tioconazole, are dissolved in propylene glycol at 50° to 60° C. and the propylene glycol mix is added to the cooled melt described above. While mixing the above mixture, benzyl alcohol (if present) is added and then water is added to bring the mix up to the desired weight. Mixing is continued and the mix is de-aerated under vacuum and cooled to form the cream formulation of the invention. 
     The following Examples represent preferred embodiments of the present invention. Unless otherwise indicated, all temperatures are expressed in degrees Centigrade. 
    
    
     EXAMPLE 1 
     A tipredane-tioconazole cream formulation having the following composition was prepared as described below. 
     
         ______________________________________Tipredane-Tioconazole CreamIngredient             Amount (mg)______________________________________Tipredane micronized powder (to                  1supply 1.0 mg/g activity)Tioconazole            10Glyceryl stearate (emulsifier)                  70Cetyl alcohol NF (emulsifier)                  50White wax (thickener for proper                  30consistency)Isopropyl isostearate (emollient)                  33Tween 60 (polysorbate 60-emulsifier)                  40Propylene glycol USP (solubilizer-                  150preservative)Silicone DC200 fluid (350CS)(lubricant-defoamer)   10Sodium citrate USP (buffer)                  5Disodium edetate dihydrate USP                  0.05(chelating agent-antioxident)Sodium metabisulfite CP (antioxidant)                  0.2Aluminum hydroxide conc. wet gel                  4(emulsifier-water)Benzyl alcohol (preservative)                  10Purified water USP (or equivalent) ca.                  586(sufficient quantity to make 1 g)______________________________________ 
    
     All components except tipredane, tioconazole, propylene glycol and benzyl alcohol were heated and melted at 80° to 85° C. and homogenized for 20 minutes. The mix was then cooled to 50° to 55° C. by air-drying. 
     The tipredane with tioconazole were dissolved in the propylene glycol at 50° to 60° C. and the propylene glycol mix was added to the previously formed cooled melt. While mixing the above mixture, benzyl alcohol was added and then water was added to bring the mix up to the desired weight. Mixing was continued and the mix was de-aerated under vacuum and cooled to form the cream formulation of the invention. 
     The above tipredane-tioconazole cream formulation was found to be a soft cosmetically elegant and non-greasy cream product which had excellent chemical and physical stability and did not undergo syneresis even after prolonged periods of storage at temperatures of 5° C., 25° C. and 40° C. 
     EXAMPLE 2 
     A 0.1% w/w tipredane cream formulation having the following composition was prepared employing a procedure similar to that as described in Example 1 except that tioconazole is not employed. 
     
         ______________________________________Tipredane Cream 0.1 W/WIngredient             Amount (mg)______________________________________Tipredane micronized powder (to                  1supply 1.0 mg/g activity)Glyceryl stearate (emulsifier)                  70Cetyl alcohol NF (emulsifier)                  50White wax (thickener for proper                  30consistency)Isopropyl isostearate  33Tween 60 (polysorbate 60-emulsifier)                  40Propylene glycol USP (solubilizer-                  150preservative)Silicone DC200 fluid (350CS)                  10(lubricant-defoamer)Sodium citrate USP (buffer)                  5Disodium edetate dihydrate USP                  0.05(chelating agent-antioxident)Sodium metabisulfite CP (antioxidant)                  0.2Aluminum hydroxide conc. wet gel                  4(emulsifier-water)Benzyl alcohol (preservative)                  10Purified water USP (or equivalent) ca.                  595(sufficient quantity to make 1 g)______________________________________ 
    
     The above cream formulation is a soft cosmetic type non-greasy cream product which has excellent physical stability and chemical stability. 
     EXAMPLE 3 
     A tipredane cream formulation having the following composition is prepared as described in Example 1 except that isopropyl palmitate is employed in place of isopropyl isostearate. 
     
         ______________________________________Ingredient             mg/g______________________________________Tipredane              1Glyceryl monostearate (wax phase/                  70emulsion stabilizer)Cetyl alcohol (wax phase)                  50White wax (also known as beeswax)                  30(wax phase)Isopropyl palmitate (emollient)                  30Tween 60 (emulsifier)  40Propylene glycol USP (solubilizer,                  150humectant, preservative)Silicone fluid DC 200  10(lubricant, antifoam)Sodium citrate USP (pH adjuster)                  5Disodium edetate dihydrate                  0.05(chelating agent)Sodium metabisulfite (antioxidant)                  0.2Aluminum hydroxide conc. wet gel                  4(pH adjuster)Benzyl alcohol (preservative)                  7.5Purified water to 1.0 g.______________________________________ 
    
     The above cream formulation is a soft cosmetic type non-greasy cream product which has excellent physical and chemical stability.