Clotrimazole Cream
Clotrimazole Cream contains NLT 90.0% and NMT 110.0% of the labeled amount of clotrimazole (C22H17ClN2).
•  The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.
•  Procedure
Buffer:  4.35 mg/mL of dibasic potassium phosphate
Mobile phase:  Acetonitrile and Buffer (3:1)
[Note—The ratio of volumes may be changed to obtain the required resolution. ]
Standard solution:  0.5 mg/mL of USP Clotrimazole RS in methanol
System suitability solution:  0.1 mg/mL each of USP Clotrimazole RS and USP Clotrimazole Related Compound A RS in methanol
Sample solution:  Transfer the equivalent of 25 mg of clotrimazole from the Cream to a 50-mL screw-capped centrifuge tube. Add 25.0 mL of methanol, and heat at 50 in a water bath for 5 min, with occasional shaking. Remove the tube from the bath, and shake vigorously for 5 min. Cool in a methanol–ice bath for 15 min, and promptly centrifuge. Transfer the supernatant to a 50-mL volumetric flask. Add 20.0 mL of methanol to the residue in the centrifuge tube, and repeat the extraction starting with “heat at 50 in a water bath”. Transfer the supernatant to the volumetric flask containing the supernatant from the first extraction, dilute with methanol to volume, and mix.
Chromatographic system 
Mode:  LC
Detector:  UV 254 nm
Column:  4.6-mm × 25-cm; 5-µm packing L1
Flow rate:  1.5 mL/min
Injection size:  25 µL
System suitability 
Samples:  Standard solution and System suitability solution
[Note—The relative retention times for clotrimazole and clotrimazole related compound A are 1.0 and 1.2, respectively. ]
Suitability requirements 
Resolution:  NLT 2.0 between clotrimazole and clotrimazole related compound A, System suitability solution
Relative standard deviation:  NMT 2.0%, Standard solution
Samples:  Standard solution and Sample solution
Calculate the percentage of C22H17ClN2 in the portion of Cream taken:
Result = (rU/rS) × (CS/CU) × 100
rU== peak response of clotrimazole from the Sample solution
rS== peak response of clotrimazole from the Standard solution
CS== concentration of USP Clotrimazole RS in the Standard solution (mg/mL)
CU== nominal concentration of clotrimazole in the Sample solution (mg/mL)
Acceptance criteria:  90.0%–110.0%
•  Packaging and Storage: Preserve in collapsible tubes or tight containers, at a temperature between 2 and 30.
•  Labeling: Cream that is packaged and labeled for use as a vaginal preparation shall be labeled Clotrimazole Vaginal Cream.
•  USP Reference Standards 11
USP Clotrimazole RS Click to View Structure
USP Clotrimazole Related Compound A RS
    C19H15ClO        294.78
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Behnam Davani, Ph.D., M.B.A.
Senior Scientific Liaison
(SM12010) Monographs - Small Molecules 1
Reference Standards RS Technical Services
USP35–NF30 Page 2741
Pharmacopeial Forum: Volume No. 35(6) Page 1451