Clotrimazole Cream
»Clotrimazole Cream contains not less than 90.0percent and not more than 110.0percent of the labeled amount of clotrimazole (C22H17ClN2).
Packaging and storage— Preserve in collapsible tubes or tight containers,at a temperature between 2and 30.
Labeling— Cream that is packaged and labeled for use as a vaginal preparation shall be labeled Clotrimazole Vaginal Cream.
Identification— In a suitable chromatographic chamber,arranged for thin-layer chromatography (see Chromatography á621ñ)containing 200mLof ether,place a beaker containing 25mLof ammonium hydroxide.Cover the chamber,and allow to equilibrate for 2hours.Place a portion of Cream,equivalent to about 5mg of clotrimazole,in a 50-mLcentrifuge tube,add 5mLof chloroform,mix,and centrifuge to obtain a clear test solution.Apply 20µLof the lower,chloroform phase and 20µLof a solution of USP Clotrimazole RSin chloroform containing 1mg per mLto a suitable thin-layer chromatographic plate (see Chromatography á621ñ),coated with a 0.25-mm layer of chromatographic silica gel mixture.Develop the chromatogram until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow the solvent to evaporate.Locate the spots on the plate by examination under short-wavelength UVlight:the RFvalue of the principal spot from the test solution corresponds to that obtained from the Standard solution.Dissolve 3g of bismuth subnitrate and 30g of potassium iodide in 10mLof dilute hydrochloric acid (1in 4),dilute with water to 100mL,mix,and prepare a spray reagent by diluting 10mLof this solution and 5mLof dilute hydrochloric acid (1in 4)with water to 200mL,and mixing.Spray the plate evenly with this spray reagent:the principal spots from the test solution and the Standard solution are orange.
Assay—
Dibasic potassium phosphate solution andMobile phase— Prepare as directed in the Assayunder Clotrimazole.
Internal standard solution— Prepare a solution of testosterone propionate in dehydrated alcohol having a concentration of about 0.07mg per mL.
Standard stock solution— Transfer about 50mg of USP Clotrimazole RS,accurately weighed,to a 50-mLvolumetric flask,dilute with dehydrated alcohol to volume,and mix.
Standard preparation— Mix 10.0mLof Standard stock solutionand 10.0mLof Internal standard solution.
Resolution solution— Prepare a solution of USP Clotrimazole Related Compound A RSin dehydrated alcohol having a concentration of about 0.12mg per mL.Mix 7mLof this solution and 1mLof Standard stock solution.
Assay preparation— Accurately weigh a portion of Cream,equivalent to about 10mg of clotrimazole,and transfer to a 50-mLscrew-capped centrifuge tube.Add 10.0mLof Internal standard solution,and heat at 50in a water bath for 5minutes,with occasional shaking.Remove the tube from the bath,and shake vigorously for 5minutes.Cool in a methanol-ice bath for 15minutes,and promptly centrifuge.Transfer the supernatant to a test tube.Add 10.0mLof dehydrated alcohol to the residue in the centrifuge tube,and repeat the extraction starting with “heat at 50in a water bath”.Transfer the supernatant to the test tube containing the supernatant from the first extraction,and mix.Use this solution as the Assay preparation.
Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 2.1-mm ×6-cm guard column that contains 10-µm packing L7and a 3.9-mm ×30-cm analytical column that contains 10-µm packing L1.The flow rate is about 1mLper minute.Chromatograph the Resolution solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.9for clotrimazole related compound Aand 1.0for clotrimazole;and the resolution,R,between clotrimazole related compound Aand clotrimazole is not less than 1.2.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 1.0for clotrimazole and 1.5for testosterone propionate;and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of clotrimazole (C22H17ClN2)in each g of Cream taken by the formula:
20(C/W)(RU/RS),
in which Cis the concentration,in mg per mL,of USP Clotrimazole RSin the Standard preparation;Wis the weight,in g,of Cream taken;and RUand RSare the peak response ratios of clotrimazole to testosterone propionate obtained from the Assay preparationand the Standard preparation,respectively.
Auxiliary Information— Staff Liaison:Behnam Davani,Ph.D.,MBA,Senior Scientist
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 520
Pharmacopeial Forum:Volume No.27(2)Page 2131
Phone Number:1-301-816-8394