in general , this invention comprises a synergistic combination of a specific imidazole derivative and zinc oxide . the term &# 34 ; synergistic combination &# 34 ; as used herein refers to a mixture of two discrete compounds which display a degree of total activity which is greater than the average of the sum of the activity of the compounds taken individually . the specific imidazole derivative which has been found useful in the present invention is miconazole nitrate of the formula . ## str1 ## this compound and a method of preparation are more fully described in u . s . pat . no . 3 , 717 , 655 , which is incorporated herein by reference . these compounds can be prepared by preparing a suspension of α -( 2 , 4 - dichlorophenyl )- imadazole - 1 - ethanol and sodium hydride in dry tetrahydrofuran . this suspension is stirred and refluxed for two hours and after this reaction time , the evolution of hydrogen is ceased . then there are added successively dimethylformamide and 2 , 4 - dichlorobenzylchloride and stirring and refluxing is continued for an additional two hours . the tetrahydrofuran is removed at atmospheric pressure and the dimethylformamide solution is poured into water . the product is extracted with benzene , washed with water , dried , filtered and evaporated in vacuo . from the residual oily - free base , the nitrate is prepared in the usual manner in 2 - propanol by treatment with concentrated nitric acid , yielding , after recrystallization , the miconazole nitrate . the other compound in the synergistic combination is a pharmaceutical grade of zinc oxide which is readily available from a number of commercial sources . the ratio of the miconazole nitrate to zinc oxide in the synergistic combinations of this invention can vary from about 1 : 40 to 1 : 1900 , preferably from about 1 : 60 to 1 : 1900 . a most preferred embodiment would have a ratio of miconazole nitrate to zinc oxide of about 1 : 60 . although the synergistic combinations of the invention may be used in various compositions , they are particularly useful in skin care compositions in an ointment , cream or lotion form . in such compositions they are combined with known ingredients normally utilized in such compositions including but not limited to carriers and vehicles , lubricants , emollients , emulsifiers , thickeners , powders , coloring , perfumes and the like . the synergistic combinations of the present invention may be incorporated into various compositions separately or they may first be premixed and then added . they may be added in either aqueous or oleaginous media . it is customary but not essential to mill or homogenize the compositions containing the synergistic combinations to ensure uniformity and smooth , non - gritty dispersions . frequently , a thickener or stabilizer is added to prevent settling of the synergistic combinations and the resulting non - uniformity of the finished product upon standing . combinations containing about 0 . 25 % miconazole nitrate and 15 . 0 % zinc oxide have been demonstrated to be synergistic and particularly effective . it is fully expected that combinations containing higher concentrations of the components and ratios greater than 1 : 60 , miconazole nitrate to zinc oxide , would also be synergistic and effective even though such concentrations and ratios are presently believed to be therapeutically unnecessary . specific embodiments of the compositions prepared in accordance with the present invention are illustrated by the following representative examples . it will be understood , however , that the invention is not confined to the specific limitations set forth in the individual examples , but rather to the scope of the appended claims . a cream skin care composition is prepared by adding into a suitable container 36 . 74 g . mineral oil , 5 . 5 g . anhydrous lanolin , 8 . 0 g . white wax , 4 . 57 g . paraffin hard wax , 7 . 0 g . synthetic beeswax , 1 . 0 g . glyceryl monostearate , 6 . 85 g . ceresine wax , and 15 . 0 zinc oxide . the mixture is heated to 70 ° c . and stirred until uniform and then added with vigorous stirring to a mixture of 0 . 9 g . borax , 0 . 25 g . miconazole nitrate , 0 . 1 g . propylparaben and 13 . 93 g . deionized water at 70 ° c . the resulting emulsion is cooled to 50 ° c . and 0 . 16 g . fragrance is added and the emulsion is cooled to 40 ° c . and placed in suitable containers . ______________________________________ % by wt . ______________________________________mineral oil 36 . 74lanolin , anhydrous 5 . 50white wax 8 . 00paraffin hard wax 4 . 57synthetic beeswax 7 . 00glyceryl monostearate 1 . 00ceresine wax 6 . 85zinc oxide 15 . 00borax 0 . 90miconazole nitrate 0 . 25fragrance 0 . 16propylparaben 0 . 10deionized water qs . to 100______________________________________ an ointment skin care composition is prepared by placing 34 . 85 g . petrolatum , 3 . 0 g . polyethylene , 33 . 8 g . cyclomethicone , 10 . 0 g . dimethicone , 1 . 0 g . mineral oil , 2 . 0 g . silicon dioxide , 0 . 1 g . propylparaben , 15 . 0 g . zinc oxide and 0 . 25 g . miconazole nitrate in a suitable vessel and heating to 60 ° c . the resulting composition is homogenized and cooled to 35 ° c . and filled into suitable containers . ______________________________________ % by wt . ______________________________________petrolatum 34 . 85polyethylene 3 . 00cyclomethicone 33 . 80dimethicone 10 . 00mineral oil 1 . 00silicon dioxide 2 . 00propylparaben 0 . 10zinc oxide 15 . 00miconazole nitrate 0 . 25 100 . 00______________________________________ a lotion skin care composition is prepared by placing in a suitable mixing vessel 69 . 80 g . deionized water and dispersing therein 0 . 3 g . carbopol 934 . 4 . 0 g . propylene glycol are added and the mixture is heated to 80 ° c . while maintaining the temperature at 80 ° c ., 1 . 0 g . of isopropyl palmitate , 1 . 25 g . oleic acid , 0 . 8 g . sorbitan stearate , 0 . 5 g . cetyl alcohol , 0 . 5 g . stearyl alcohol , 0 . 5 g . synthetic beeswax , 1 . 25 g . glyceryl stearate , 1 . 25 g . stearic acid , 1 . 2 g . polysorbate 61 and 1 . 5 g . myristyl myristate are added . this is followed by the addition of 0 . 13 g . sodium hydroxide , 0 . 05 g . butylparaben , 0 . 1 g . propylparaben , 0 . 15 g . methylparaben and 0 . 02 g . butylated hydroxytoluene . the resulting emulsion is cooled to 50 ° c . and 0 . 3 g . benzyl alcohol , 15 . 0 g . zinc oxide , 0 . 25 g . miconazole nitrate and 0 . 15 g . fragrance and coloring are added . the resulting composition is homogenized and cooled to room temperature . ______________________________________ % by wt . ______________________________________carbopol 934 ( b . f . goodrich &# 39 ; s tradename 0 . 30for a polymer of acrylic acid cross - linked with a polyfunctional agent ) propylene glycol 4 . 00isopropyl palmitate 1 . 00oleic acid 1 . 25sorbitan stearate 0 . 80cetyl alcohol 0 . 50stearyl alcohol 0 . 50synthetic beeswax 0 . 50glyceryl stearate 1 . 25stearic acid 1 . 25polysorbate 61 ( polyoxyethylene ( 21 ) 1 . 20sorbitan mono - oleate ) myristyl myristate 1 . 50sodium hydroxide 0 . 13butylparaben 0 . 05propylparaben 0 . 10methylparaben 0 . 15butylated hydroxytoluene 0 . 02benzyl alcohol 0 . 30zinc oxide 15 . 00miconazole nitrate 0 . 25fragrance and coloring 0 . 15deionized water g . s . to 100______________________________________ an ointment skin care composition is prepared in accordance with the procedure of example ii and has the following formulation : ______________________________________ % by w / w______________________________________white petrolatum 84 . 75zinc oxide 15 . 00miconazole nitrate 0 . 25 100 . 00______________________________________ an ointment skin care composition is prepared in accordance with the procedure of example ii and has the following formulation : ______________________________________ % wt / wt______________________________________white petrolatum 81 . 35zinc oxide 15 . 00thixcin r ( nl chemical &# 39 ; s tradename 3 . 00for trihydroxystearin ) miconazole nitrate 0 . 25fragrance 0 . 40 100 . 00______________________________________ the synergistic efficacy of the combinations of the present invention can be established by the following in - vivo test procedure : utilizing zinc oxide and miconazole nitrate in a base consisting of petrolatum and a biologically inert thickener . in this test the base containing 15 % zinc oxide , the base containing 0 . 25 % miconazole nitrate and the base containing both 0 . 25 % miconazole nitrate and 15 % zinc oxide are compared using the following procedure . twenty microliters of a saline suspension of c . albicans containing 1 million cells per milliliter are applied to three one square centimeter test sites on the volar forearm surface of each volunteer subject . the areas are covered with an impermeable plastic film and secured with tape . the test sites are uncovered six hours after inoculation and treated with one of the test products or left untreated as a control . the sites are then redressed with plastic film for an additional 24 hours . the test products are then removed from all sites and cultures are obtained by a standard detergent scrub method . clinical measuremehts are obtained for each site immediately prior to treatment , at 24 hours and at 48 hours after treatment . grading is done on a scale of 0 = no reaction , 1 = minute pinpoint papules and / or faint erythema , 2 = at least 5 discrete papules or pustules and definite erythema , 3 = greater than 10 papules or pustules and erythema , 4 = confluent papules or pustules and intense erythema . the results show a statistically significant synergistic effect for the base containing the combination of miconazole nitrate and zinc oxide at a ratio of about 1 : 60 compared to the sum of the bases each containing only one of the components . a quantitative technique can be used to determine the synergistic effect of zinc oxide on the ability of miconazole nitrate to inhibit the growth of staphylococcus aureus and candida albicans . this technique consists of preparing weighed suspensions of zinc oxide and / or miconazole nitrate in measured volumes of melted microbial growth supporting agars . aliquots of these agar suspensions are transferred to petri plates and allowed to solidify . during the solidifying process , the zinc oxide and / or miconazole nitrate particles are maintained in suspension in the agar in the petri plates by imparting constant motion to the plates positioned on a reciprocating or rotary platform shaker . to the surface of the solidified agar suspension is added 0 . 02 - 0 . 1 ml of inoculum of c . albicans or of s . aureus containing approximately 300 colony forming units ( cfu )/ volume of microbial suspension added ( 1 . 5 × 10 4 - 3 × 10 3 cfu / ml , respectively ). the organisms are then distributed evenly over the agar surface with a sterile glass spreader . the s . aureus plates are incubated 2 to 4 days at 35 ° c . and the c . albicans plates are incubated 5 to 7 days at 25 ° c . after the incubation period , the plates are examined for evidence of growth inhibition by determining the presence or absence of surface colonies . the number of colonies on each plate at each concentration of miconazole nitrate alone is noted . similarly the number of colonies is noted on each plate at each concentration of zinc oxide alone , and on plates containing combinations of different concentrations of both miconazole nitrate and zinc oxide . the &# 34 ; percent inhibition &# 34 ; of the bacteria or of the yeast produced at ony one concentration of miconazole nitrate alone is calculated by comparing the number of colonies obtained at that concentration with the number of colonies of the negative control plate containing no zinc oxide or miconazole nitrate . similarly , the &# 34 ; percent inhibition &# 34 ; produced at one concentration of zinc oxide alone is calculated by comparing the number of colonies obtained at that concentration of zinc oxide with the number of colonies produced on the negative control plates containing no miconazole nitrate or zinc oxide . to determine the effect of zinc oxide on miconazole nitrate activity , the &# 34 ; percent inhibition &# 34 ; of the organisms in contact with any of the combinations of zinc oxide and miconazole nitrate concentrations are calculated by relating the number of surviving colonies on the agar surface of those plates with the number of surviving colonies on the base line control plates containing the same concentration of zinc oxide alone . when the zinc oxide and miconazole nitrate combinations are tested according to the above procedures , the following examples of the results are obtained . these results are expressed as percent inhibition of the organism at a specific concentration of miconazole nitrate alone ( inhibition for miconazole ); as percent inhibition of the organism at a specific concentration of zinc oxide alone ( inhibition for zinc oxide ); as the percent inhibition expected if the inhibition obtained for miconazole nitrate and for zinc oxide were additive ( sum of components ), and as the observed inhibition at specific concentrations of zinc oxide and miconazole nitrate ( inhibition for combination ). after observation of a repeated 100 . 0 % inhibition , no further ratios are tested at the stated concentrations of miconazole nitrate and zinc oxide . table i______________________________________synergistic activity of zinc oxide on miconazole nitrateinhibition of the growth of staphylococcus aureus atmiconazole nitrate concentration of 0 . 75 × 10 . sup .- 4 % w / vzinc oxide inhibition inhibitionconcen - for inhibition sum of fortration × miconazole for compo - combina - 10 . sup .- 2 % w / v nitrate zinc oxide nents tion______________________________________0 . 00 14 . 6 0 . 0 14 . 6 14 . 60 . 21 14 . 6 7 . 0 21 . 6 17 . 40 . 42 14 . 6 15 . 1 29 . 7 29 . 70 . 83 14 . 6 40 . 2 54 . 8 100 . 01 . 67 14 . 6 56 . 9 71 . 5 100 . 02 . 50 14 . 6 78 . 9 93 . 5 100 . 0______________________________________ these results exhibit synergism at ratios of from about 1 : 110 to 1 : 333 , miconazole nitrate to zinc oxide . if ratios above 1 . 333 were to be tested at the same concentrations , 100 . 0 % inhibition would be observed . synergistic activity of zinc oxide on miconazole nitrate inhibition of the growth of staphylococcus aureus at miconazole nitrate concentration of 0 . 75 × 10 - 4 % w / v table ii______________________________________synergistic activity of zinc oxide on miconazole nitrateinhibition of the growth of staphylococcus aureus atmiconazole nitrate concentration of 0 . 75 × 10 . sup .- 4 % w / vzinc oxide inhibition inhibitionconcen - for inhibition sum of fortration × miconazole for compo - combina - 10 . sup .- 2 % w / v nitrate zinc oxide nents tion______________________________________0 . 00 21 . 1 0 . 0 21 . 1 21 . 10 . 16 21 . 1 11 . 4 32 . 5 13 . 20 . 31 21 . 1 14 . 1 35 . 2 39 . 60 . 63 21 . 1 18 . 2 39 . 3 97 . 71 . 25 21 . 1 38 . 6 59 . 7 100 . 02 . 50 21 . 1 61 . 7 82 . 8 100 . 0______________________________________ these results exhibit synergism at ratios of from about 1 : 40 to 1 : 333 , miconazole nitrate to zinc oxide . if ratios about 1 . 333 were to be tested at the same concentrations , 100 . 0 % inhibition would be observed . synergistic activity of zinc oxide on miconazole nitrate inhibition of the growth of candida albicans at miconazole nitrate concentration of 3 . 13 × 10 - 4 % w / v table iii______________________________________synergistic activity of zinc oxide on miconazole nitrateinhibition of the growth of candida albicans at miconazolenitrate concentration of 3 . 13 × 10 . sup .- 4 % w / vzinc oxide inhibition inhibitionconcen - for inhibition sum of fortration × miconazole for compo - combina - 10 . sup .- 2 % w / v nitrate zinc oxide nents tion______________________________________ 0 . 00 15 . 4 0 . 0 15 . 4 15 . 4 3 . 75 15 . 4 2 . 0 17 . 4 16 . 4 7 . 50 15 . 4 2 . 0 17 . 4 31 . 415 . 00 15 . 4 2 . 0 17 . 4 46 . 330 . 00 15 . 4 2 . 0 17 . 4 100 . 060 . 00 15 . 4 2 . 0 17 . 4 100 . 0______________________________________ these results exhibit synergism at ratios of from about 1 : 240 to 1 : 1900 , miconazole nitrate to zinc oxide . synergistic activity of zinc oxide on miconazole nitrate inhibition of the growth of candida albicans at miconazole nitrate concentrations of 3 . 13 × 10 - 4 % w / v table iv______________________________________synergistic activity of zinc oxide on miconazole nitrateinhibition of the growth of candida albicans at miconazolenitrate concentration of 3 . 13 × 10 . sup .- 4 % w / vzinc oxide inhibition inhibitionconcen - for inhibition sum of fortration × miconazole for compo - combina - 10 . sup .- 2 % w / v nitrate zinc oxide nents tion______________________________________ 0 . 00 10 . 4 0 . 0 10 . 4 10 . 4 3 . 75 10 . 4 3 . 0 13 . 4 22 . 2 7 . 50 10 . 4 3 . 0 13 . 4 41 . 815 . 00 10 . 4 3 . 0 13 . 4 67 . 430 . 00 10 . 4 3 . 0 13 . 4 100 . 060 . 00 10 . 4 3 . 0 13 . 4 100 . 0______________________________________ these results exhibit synergism at ratios of from about 1 : 120 to 1 : 1900 , miconazole nitrate to zinc oxide . various other features and embodiments of the present invention not specifically set forth herein will be readily obvious to those skilled in the art , all of which may be achieved without departing from the spirit and scope of the invention as defined by the following claims .
a skin care composition having improved effectiveness in preventing and treating acute inflammatory skin conditions comprising miconazole nitrate and zinc oxide .