unless otherwise indicated , all ingredient concentrations are listed as percent ( w / w ). ciprofloxacin is present in the compositions of the invention in an amount effective for anti - bacterial action . such amounts range from about 0 . 01 - 1 %, preferably from about 0 . 1 - 0 . 5 %, and most preferably about 0 . 2 %. compositions of the present invention also comprise hydrocortisone as an anti - inflammatory agent . hydrocortisone is present in an amount effective for anti - inflammatory action . such amount typically ranges from about 0 . 1 - 3 %, preferably about 0 . 1 - 2 %, and most preferably about 1 %. particularly for ophthalmic use , small particle sizes are preferred . as used herein , “ micronized ” hydrocortisone means hydrocortisone particles having an average particle size ≦ 10 μm ( based on surface area ( dsn )). if the particle size of the hydrocortisone raw material as received from the supplier is unsatisfactory , one or more known sizing techniques , such as ball milling or micronizing , can be used to adjust the particle size into the desired range . to prevent contamination by microorganisms and provide a reasonable shelf - life , the compositions of the present invention include a preservative . acceptable preservatives are required to cause no or insignificant ototoxicity , sensitization or irritation of the ear . additionally , the preservative must be jointly soluble with ciprofloxacin in water over a ph range of approximately ph 3 - 6 . the most preferred preservative is benzyl alcohol , which is typically present in an amount from about 0 . 1 - 3 %, preferably about 0 . 1 - 2 %, and most preferably about 0 . 9 %. a tonicity adjusting agent is preferably contained in an amount sufficient to cause the composition to be approximately isotonic , that is an amount effective to adjust the tonicity of the composition from about 150 - 800 mosm , preferably 200 - 600 mosm . a preferred tonicity - adjusting agent is sodium chloride . a buffering agent is desirable for the compositions of the present invention . the preferred buffering system is an acetate buffer comprising acetic acid and sodium acetate . amounts of sodium acetate and acetic acid effective to buffer the preparation in a ph range of about 4 . 0 - 5 . 3 , preferably about 4 . 4 - 4 . 9 and most preferably about 4 . 7 , range from about 0 . 1 - 3 % of sodium acetate and from about 0 . 01 - 10 % of acetic acid . preferably the amount of sodium acetate is from about 0 . 1 - 2 % and most preferably about 0 . 6 - 0 . 7 %. preferably the amount of sodium acid is about 0 . 1 - 5 % and most preferably about 0 . 2 - 0 . 3 %. sodium acetate is preferably used in the form of sodium acetate trihydrate and acetic acid is preferably used in the form of glacial acetic acid . to allow the compositions of the present invention to wet and spread on the skin surface at the site of infection or inflammation in the ear canal , a non - ionic surfactant is desirable . the surfactants known as polysorbates , in particular polysorbates 20 to 80 , are preferred . such polysorbates are commercially available under the tradename tween from ici americas , inc . most preferred is polysorbate 20 . the amount of polysorbate surfactant contained in the compositions of the present invention generally ranges from about 0 . 01 - 2 %, preferably about 0 . 05 - 1 %, and most preferably about 0 . 1 %. to help maintain or improve the physical stability of the suspension composition of the present invention , lecithin or a lecithin derivative is added . lecithins from natural / vegetative ( e . g ., egg or soy lecithin ) and synthetic origins are known . the primarily type of lecithin is phosphatidylcholine ( pc ). other types of lecithins include phosphatidylglycerol ; phosphatidylinositol ; sphingomyelin ; and phosphatidylethanolamine . derivatives of lecithin with saturated and unsaturated fatty acid side chains on pc , are also known , including : distearoylphosphatidyl choline ; dipalmitoylphosphatidyl choline ; and dimirystoylphosphatidyl choline . as used herein , “ lecithin ” includes such derivatives of lecithin . preferably , the lecithin ingredient comprises at least 75 % pc . commercially available grades of soy lecithins include a fully hydrogenated soy lecithin comprising 90 % phosphatidylcholine available under the tradename phospholipon 90h from american lecithin company and a soy lecithin comprising 75 % phosphatidylcholine available under the tradename lipoid - s75 from vernon walden , inc . the amount of lecithin contained in the compositions of the present invention depends primarily on the concentration of insoluble ingredients in the compositions . the amount of lecithin in the compositions of the present invention generally ranges from about 0 . 01 - 5 %, preferably about 0 . 01 - 2 % and most preferably is about 0 . 15 %. in addition to the excipients mentioned above , the ciprofloxacin and hydrocortisone compositions of the present invention optionally comprise polyvinyl alcohol as a viscosity - augmenting agent . the polyvinyl alcohol contained in the composition of the present invention should be at least 85 % hydrolyzed , with grades ranging from 85 % hydrolyzed to 99 +% hydrolyzed being suitable . most preferred is an 88 % hydrolyzed grade of polyvinyl alcohol , such as that commercially available as airvol 205s from air products and chemicals , inc . the amount of polyvinyl alcohol ingredient in the compositions of the present invention is preferably an amount effective to cause the composition to have a viscosity ranging from about 2 - 8 cps ( when measured at room temperature using a brookfield viscometer set at 30 rpm and a cp 42 spindle ). preferably , the polyvinyl alcohol ingredient is present in an amount sufficient to cause the composition &# 39 ; s viscosity to be from about 3 - 7 cps . the compositions of the present invention are prepared in a specific manner . it is essential that the hydrocortisone ingredient is first mixed with lecithin for greater than 45 minutes prior to combining the hydrocortisone ingredient with the remainder of the composition . preferably , hydrocortisone is mixed with both lecithin and a polysorbate 20 to 80 surfactant before combining hydrocortisone with the remainder of the composition . the presence of the polysorbate surfactant provides a lower viscosity slurry than simply mixing hydrocortisone and lecithin alone . the lower viscosity achieved by the addition of the polysorbate surfactant makes processing easier . as mentioned above , hydrocortisone is preferably sized to achieve desirable particle sizes . the hydrocortisone ingredient in the compositions of the present invention can be sized in the presence of lecithin and optionally a polysorbate 20 to 80 surfactant . if the hydrocortisone ingredient is sized prior to mixing with lecithin , then the mixing with lecithin step must occur prior to combining hydrocortisone with the remainder of the ciprofloxacin and hydrocortisone composition . particle sizing techniques are known in the art and include ball milling , homogenization and micronization . as used herein , “ mixing ” includes simple mixing as well as sizing procedures . the lecithin ingredient should be dispersed in water at a temperature above the phase transition temperature for the chosen grade of lecithin . in the case of phospholipon 90h , the phase transition temperature is approximately 51 ° c . therefore , phospholipon 90h is preferably dispersed at a temperature of approximately 65 - 70 ° c . a polysorbate surfactant , if present , can be dispersed simultaneously with lecithin or added before or after lecithin is fully dispersed . after the polysorbate surfactant and lecithin are dispersed , hydrocortisone ( preferably micronized ) is then dispersed . the hydrocortisone is preferably added after removing the lecithin dispersion from heat , but before the lecithin dispersion cools to room temperature . the hydrocortisone ingredient is preferably mixed with the lecithin dispersion for approximately 6 to 18 hours or more , and most preferably about 12 hours , before being added to the remainder of the ciprofloxacin / hydrocortisone composition . in a separate vessel , ciprofloxacin is dissolved in water with an acetate buffer , then the benzyl alcohol preservative , sodium chloride tonicity adjusting agent and the polyvinyl alcohol viscosity augmenter are sequentially added , with each ingredient being dispersed or dissolved prior to the addition of the next . although it is possible to add all of these ingredients simultaneously rather than sequentially provided that the vessel contains a sufficient amount of water , sequentially mixing and dispersing is preferred . after the ciprofloxacin solution has been prepared , it is combined with the hydrocortisone slurry then the ph is adjusted with naoh or hcl and the batch volume is adjusted with purified water . 1 . add approx . 5 - 50 % of the total batch volume of purified water to a compounding vessel and heat to a temperature above the transition temperature of the chosen grade of lecithin ( in the case of phospholipon 90h the preferred temperature is approximately 65 - 70 ° c .). 2 . using a magnetic stir bar , disperse 50 % of the total required amount of lecithin ( preferably , phospholipon 90h ) and 50 % of the total required amount of surfactant ( preferably polysorbate 20 ) into the heated water of step 1 until uniformly dispersed ( generally about 10 - 20 min .). remove from heat . 3 . add the hydrocortisone ( preferably micronized hydrocortisone ) before the dispersion of step 2 cools to room temperature and mix for approximately 12 hrs . ( i . e ., overnight ). 4 . prepare a ciprofloxacin solution by adding the following components in order and mix well allowing each to disperse or dissolve before adding the next : the remaining 50 % of the total amount of lecithin ( at elevated temperature ), the remaining 50 % of the total amount of surfactant , the preservative , the buffer ( e . g ., glacial acetic acid then sodium acetate ( trihydrate )), ciprofloxacin , and the tonicity - adjusting agent , and optionally polyvinyl alcohol ( from stock solution ). 5 . prepare a stock solution of polyvinyl alcohol in purified water . the stock solution is preferably prepared at a polyvinyl alcohol concentration of about 0 . 5 or 1 . 0 % and preferably prepared at 90 - 95 ° c . ( for easier and faster solution preparation ) then cooled to room temperature . 6 . add the hydrocortisone dispersion of step 3 to the ciprofloxacin solution of step 4 ( while mixing ), then mix in the required amount of polyvinyl alcohol stock solution . 8 . measure and adjust ph to about 4 . 7 with 1n naoh and / or 1n hcl , then qs to 100 % with purified water . 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 . a . polyvinyl alcohol and lecithin are dissolved in purified water , which has been heated to 90 - 95 ° c . this solution is cooled to 50 ° c . before benzyl alcohol is added and dispersed . the solution is cooled to room temperature . b . hydrocortisone is dispersed in a mixture of polysorbate 20 and purified water in a second container . the mixture is homogenized to assure uniform distribution of individual particles in the pre - mix . c . the sodium acetate and glacial acetic acid are dissolved in purified water in a third container , ciprofloxacin hcl is then added and dissolved in this buffer . d . sodium chloride is dissolved in purified water in a fourth container . the contents of each container are pumped through a polishing filter into the mixing tank in the order given . if necessary , 1n naoh or 1n hcl is added to adjust ph to 4 . 7 , prior to bringing to final volume . 1 . weigh out and add all of the specified amount of hydrocortisone to a 30 ml polypropylene milling bottle . 2 . weigh out and add 50 % of the specified amount of 1 % polysorbate 20 stock solution and 50 % of the specified amount of lecithin ( phospholipon 90h ) and heat to approximately 65 - 70 ° c . to disperse the lecithin homogeneously . 3 . transfer the solution of polysorbate 20 and phospholipon 90 h mixture to the milling bottle . 4 . weigh out and add 75 . 0 g of zirconia - y beads ( 3 mm ) to the milling bottle . 2 . weigh and add the specified amount of polyvinyl alcohol stock solution 3 . add purified water to approximately 20 % of the total batch volume and heat to approximately 65 - 70 ° c . 4 . weigh and add the remaining amount of lecithin ( phospholipon ) and disperse by simple stirring at 65 - 70 ° c . 6 . add the following ( in order ) with stirring allowing each to dissolve / disperse completely before addition of the next : benzyl alcohol , glacial acetic acid , sodium acetate , ciprofloxacin hcl , sodium chloride 7 . transfer the ball milled slurry of hydrocortisone / lecithin / polysorbate 20 mixture through a suitable sieve into the compounding vessel rinsing the beads well with purified water . 8 . weigh and add the remaining amount of 1 % polysorbate 20 to the compounding vessel with stirring . 9 . qs to 95 % of total batch volume with purified water 10 . check and adjust ph to target ph of 4 . 7 with 1n sodium hydroxide and / or 1n hydrochloric acid . 11 . qs to 100 % ( 200 ml ) with purified water and allow to mix well . formulation # 2b was prepared according to the procedure used to prepare formulation # 2a except that the hydrocortisone slurry was made as follows : 1 . weigh out and add all of the required 1 % polysorbate 20 stock solution , add all of the required lecithin ( phospholipon 90h ) and heat to approximately 65 - 70 ° c . to disperse ( with stir bar ) the lecithin homogeneously . 2 . add all of the required amount of micronized hydrocortisone and mix the hydrocortisone slurry for 45 minutes using a magnetic stir bar . the vehicle was prepared according to the procedure used to prepare the vehicle for formulation # 2a except that the polyvinyl alcohol stock solution was added in step 6 ( after sodium chloride ). formulation # 2c was prepared according to the procedure used to prepare formulation # 2b except that there is no heating in the preparation of the hydrocortisone slurry . the lecithin is dispersed at room temperature instead of approximately 65 - 70 ° c . 2 . add 50 % of total batch weight of purified water to the compounding vessel . 3 . heat the purified water and maintain at approximately 65 - 70 ° c . 4 . add 50 % of the batch weight of phospholipon 90h into the compounding vessel containing water at 65 - 70 ° c . maintain the temperature for 10 - 20 minutes while stirring to make sure a homogenous dispersion of phospholipon 90h is achieved . 5 . remove from heat and add 50 % of the batch weight of polysorbate 20 ( 1 % stock solution ) to the phospholipon 90h aqueous dispersion . 6 . add hydrocortisone powder into the compounding vessel and allow mixing by simple stirring for an overnight period ( approx . 12 hours ). 7 . add the remaining components of the formula into step 6 , allowing each component to mix or dissolve well by stirring : benzyl alcohol , glacial acetic acid , sodium acetate ( trihydrate ), ciprofloxacin hydrochloride , sodium chloride , remaining phospholipon 90h , remaining polysorbate 20 and polyvinyl alcohol ( airvol 125 ) as a stock solution . 8 . qs to 90 % of the batch weight with purified water . 9 . measure and adjust ph to 4 . 7 with 1n naoh or 1n hcl , if necessary . 10 . qs to 100 % of the batch weight with purified water and stir until homogeneous . formulation # 3a was prepared using the same procedure used for formulation # 2a . formulation # 3b was prepared using the same procedure used for formulation # 2b . formulation # 4a was prepared using the same procedure used to prepare formulation # 1 : 3 . add a small amount of purified water so the volume is approximately 25 % of the total batch volume . 5 . allow the mixture to cool to room temperature and add the benzyl alcohol 7 . add the following components allowing each to dissolve before adding the next : glacial acetic acid , sodium acetate , ciprofloxacin and sodium chloride . 1 . in another beaker add the polysorbate 20 and hydrocortisone together and mix well . 3 . measure and adjust ph with 1n naoh and / or 1n hcl to the target ph of 4 . 7 . 1 . weigh out and add the specified amount of hydrocortisone to a 30 ml polypropylene milling bottle . 2 . weigh out and add 50 % of the specified amount of 1 % polysorbate 20 stock solution . 3 . weigh out and add 75 . 0 g of zirconia - y beads ( 3 mm ) to the milling bottle . 1 . tare an appropriate sized compounding vessel containing a stirring bar . 3 . add purified water to approximately 20 % of the total batch volume . 6 . add the following ( in order ) with stirring allowing each to dissolve / disperse completely before addition of the next : benzyl alcohol , glacial acetic acid , sodium acetate , ciprofloxacin hcl , sodium chloride 7 . transfer the ball milled slurry through a suitable sieve into the compounding vessel rinsing the beads well with purified water . 8 . weigh and add the remaining amount of 1 % polysorbate 20 to the compounding vessel with stirring . 9 . check and adjust ph to target ph of 4 . 7 with 1n sodium hydroxide and / or 1n hydrochloric acid . 10 . qs to 100 % ( 200 ml ) with purified water and allow to mix well . formulation # 4c was prepared using the same procedure used for formulation # 4b except that the ball milling time for the hydrocortisone slurry was extended from 18 hrs . to 72 hrs . 1 . weigh out and add the specified amount of hydrocortisone to a 30 ml polypropylene milling bottle 2 . weigh out and add 50 % of the specified amount of 1 % polysorbate 20 stock solution 3 . weigh out and add 50 % of the specified amount of sodium chloride 4 . add 75 . 0 g of zirconia - y beads ( 3 mm ) to the milling bottle 1 . tare an appropriate sized compounding vessel containing a stirring bar . 3 . add purified water to approximately 20 % of the total batch volume . 6 . add the following ( in order ) with stirring allowing each to dissolve / disperse completely before addition of the next : benzyl alcohol , glacial acetic acid , sodium acetate , ciprofloxacin hcl , remaining 50 % of sodium chloride 7 . transfer the ball milled slurry into the compounding vessel through a suitable sieve rinsing the beads well with purified water . 8 . weigh and add the remaining amount of 1 % polysorbate 20 to the compounding vessel with stirring . 9 . check and adjust ph to target ph of 4 . 7 with 1n sodium hydroxide and / or 1n hydrochloric acid . 10 . qs to 100 % ( 200 ml ) with purified water and allow to mix well . 1 . weigh out and add the specified amount of hydrocortisone to a 50 ml beaker . 2 . weigh out and add specified amount of 1 % polysorbate 20 stock solution . 3 . homogenize the mixture for 30 minutes using a polyron homogenizer at setting 6 . 1 . tare an appropriate sized compounding vessel containing a stirring bar . 3 . add purified water to approximately 20 % of the total batch volume . 6 . add the following ( in order ) with stirring allowing each to dissolve / disperse completely before addition of the next : benzyl alcohol , glacial acetic acid , sodium acetate , ciprofloxacin hcl , sodium chloride 7 . transfer the homogenized slurry into the compounding vessel rinsing the beaker well with purified water . 8 . qs to 95 % of the total batch volume using purified water . 9 . check and adjust ph to target ph of 4 . 7 with 1n sodium hydroxide and / or 1n hydrochloric acid . 10 . qs to 100 % ( 200 ml ) with purified water and allow to mix well . formulation # 4f was prepared using the same procedure used for formulation # 2a except that the slurry was ball milled for 72 hrs . instead of 18 hrs . formulation # 4g was prepared using the same procedure used for formulation # 2a . formulation # 4h was prepared using the same procedure used for formulation # 2a except that no polysorbate 20 was used in the milling slurry . all of the required amount of polysorbate 20 was added in step 8 of the vehicle preparation . formulation # 4i was prepared using the same procedure used for formulation # 2b except that the slurry was mixed overnight ( approx . 12 hrs .) instead of 45 minutes . formulation # 4j was prepared using the same procedure used for formulation # 4i except that the hydrocortisone slurry did not contain any polysorbate 20 . all of the required amount of polysorbate 20 was added in step 8 of the vehicle preparation . formulation # 4k was prepared using the same procedure used for formulation # 2b . the table below summarizes the differences in the procedures used to make the formulations . the physical stability of suspension formulations is commonly measured in two ways : resuspendability is assessed by measuring the number of inversions ( also called strokes ) required to redisperse sedimentation which forms after a sample stands undisturbed for a period of time ; and rate of settling is assessed by observing the height in millimeters of the column of sedimentation visible in a sample contained in a cylinder after shaking and then standing for a period of time . in order to record the rate of settling results , the following codes are used ( in order of increasing turbidity ): c : clear supernatant phase , lm : light milky phase ( less dense than homogeneous phase ), h : homogenous phase ( initial homogeneous phase ), d : dense phase ( more dense than homogeneous phase ), s : sediment . larger sedimentation heights indicate less separation with less supernatant liquid and less compaction of sedimentation . the physical stability of formulations 1 - 4k was evaluated according to the methods described above and the results are shown in tables 3 and 4 . as shown in table 3 , the formulations prepared according to the method of the present invention ( formulation #&# 39 ; s 2a , 3a , 4f , 4g , 4h , 4i and 4j ) have resuspendability results approximately equivalent or superior to those prepared by other methods as comparative examples ( formulation #&# 39 ; s 1 , 2b , 2c , 3b , 4a , 4b , 4c , 4d , 4e and 4k ). as shown in table 4 , the formulations of the present invention have superior rate of settling results compared to the formulations of the comparative examples . see , for example , the data shown in table 4 after 2 hours ( which represents a target manufacturing time period for allowing pumping and filling final product packages with homogeneous suspension formulations ); the formulations of the present invention are substantially homogeneous after 2 hours but the formulations of the comparative examples are not . the invention has been described by reference to certain preferred embodiments ; however , it should be understood that it may be embodied in other specific forms or variations thereof without departing from its spirit or essential characteristics . the embodiments described above are therefore considered to be illustrative in all respects and not restrictive , the scope of the invention being indicated by the appended claims rather than by the foregoing description .
this invention is directed toward a method of preparing a topical composition comprising ciprofloxacin and hydrocortisone . the method involves dispersing hydrocortisone with lecithin for greater than 45 minutes prior to combining hydrocortisone with the balance of the composition .