Clotrimazole and Betamethasone Dipropionate Cream

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

DOWNLOAD PDF HERE

1 DEFINITION

Clotrimazole and Betamethasone Dipropionate Cream contains NLT 90.0% and NMT 110.0% of the labeled amount of clotrimazole (C₂₂H₁₇CIN₂) and an amount of betamethasone dipropionate equivalent to NLT 90.0% and NMT 110.0% of the labeled amount of betamethasone (C₂₂H₂₉FO₅), in a suitable cream base.

2 IDENTIFICATION

A. The retention times of the major peaks for clotrimazole and betamethasone dipropionate of the Sample solution correspond to those of the Standard solution, as obtained in the Assay for clotrimazole and betamethasone.

3 ASSAY

3.1 PROCEDURE

Buffer: 6.6 g/L of dibasic ammonium phosphate in water

Mobile phase: Prepare a mixture of methanol and Buffer (7:3), and adjust with phosphoric acid to a pH of 7.0 ± 0.2. Pass through a membrane filter having a 0.45-µm or finer pore size, and degas.

Internal standard solution: 0.15 mg/mL of Progesterone in alcohol

Clotrimazole stock solution: 5 mg/mL of USP Clotrimazole RS in alcohol

Betamethasone dipropionate stock solution: 6.4J mg/mL of USP Betamethasone Dipropionate RS in alcohol, J being the ratio of the labeled amount of betamethasone (in mg/g) to the labeled amount of clotrimazole (in mg/g) in the Cream

Clotrimazole related compound A stock solution: 0.5 mg/mL of USP Clotrimazole Related Compound A RS in methanol

Standard solution: Transfer 1.0 mL of Clotrimazole related compound A stock solution to a suitable container, and evaporate to dryness in a water bath at room temperature under a stream of nitrogen. To the residue add 2.0 mL each of Clotrimazole stock solution, Betamethasone dipropionate stock solution, and Internal standard solution.

Sample solution: Weigh a portion of Cream equivalent to 10 mg of clotrimazole, and transfer to a screw-capped, 50-mL centrifuge tube. Add 2.0 mL of Internal standard solution and 4.0 mL of alcohol, place the cap on the tube, and heat at 60° in a water bath for 10 min, with occasional shaking. Remove the tube from the bath, cool in an ice bath for 20 min, and promptly centrifuge. Transfer a portion of the supernatant to a test tube, and use as the Sample solution.

3.1.1 Chromatographic system

(See Chromatography (621), System Suitability)

Mode: LC

Detector: UV 254 nm

Column: 4.6-mm x 25-cm; 10-µm packing L1

Flow rate: 1.7 mL/min

Injection volume: 20 µL

3.1.2 System suitability

Sample: Standard solution

[NOTE-The relative retention times for betamethasone dipropionate, clotrimazole related compound A, progesterone, and clotrimazole are about 1.0, 1.2, 1.4, and 1.7, respectively.]

3.1.3 Suitability requirements

Resolution: NLT 1.0 between betamethasone dipropionate and clotrimazole related compound A, NLT 1.5 between clotrimazole related compound A and progesterone, and NLT 1.8 between progesterone and clotrimazole

Relative standard deviation: NMT 2.0% determined from clotrimazole and betamethasone dipropionate and NMT 4.0% determined from clotrimazole related compound A

3.1.4 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of clotrimazole (CH,CIN) in the portion of Cream taken:

                Result = (R_U/R_S) x (C_S/C_U) × 100

R_U = peak response ratio of clotrimazole to progesterone from the Sample solution

R_S = peak response ratio of clotrimazole to progesterone from the Standard solution

C_S = concentration of USP Clotrimazole RS in the Standard solution (mg/mL)

C_U = nominal concentration of clotrimazole in the Sample solution (mg/mL)

Calculate the percentage of the labeled amount of betamethasone (CHFO) in the portion of Cream taken:

                Result = (R_U/R_S) x (C_S/C_U) x (M_t1/M_t2) × 100

R_U = peak response ratio of betamethasone dipropionate to progesterone from the Sample solution

R_S = peak response ratio of betamethasone dipropionate to progesterone from the Standard solution

C_S = concentration of USP Betamethasone Dipropionate RS in the Standard solution (mg/mL)

C_U = nominal concentration of betamethasone in the Sample solution (mg/mL)

M_t1 = molecular weight of betamethasone, 392.46

M_t2 = molecular weight of betamethasone dipropionate, 504.60

Acceptance criteria: 90.0%~110.0% of the labeled amount of clotrimazole (C₂₂H₁₇CIN₂); 90.0%~110.0% of the labeled amount of betamethasone (C₂₂H₂₉FO₅)

4 IMPURITIES

4.1 ORGANIC IMPURITIES: LIMIT OF CLOTRIMAZOLE RELATED COMPOUND A

Buffer, Mobile phase, Internal standard solution, Clotrimazole stock solution, Betamethasone dipropionate stock solution, Clotrimazole related compound A stock solution, Standard solution, Sample solution, Chromatographic system, and System suitability: Use as directed in the Assay.

Analysis: Using the chromatograms of the Standard solution and Sample solution as obtained in the Assay, calculate the percentage of clotrimazole related compound A in the portion of Cream taken:

                Result = (R_U/R_S) x (C_S/C_U) × 100

R_U = peak response ratio of clotrimazole related compound A to progesterone from the Sample solution

R_S = peak response ratio of clotrimazole related compound A to progesterone from the Standard solution 

C_S = concentration of USP Clotrimazole Related Compound A RS in the Standard solution (mg/mL)

C_U = nominal concentration of clotrimazole in the Sample solution (mg/mL)

Acceptance criteria: NMT 5.0%

5 PERFORMANCE TESTS

MINIMUM FILL (755): Meets the requirements

6 SPECIFIC TESTS

MICROBIAL ENUMERATION TESTS (61) and TESTS FOR SPECIFIED MICROORGANISMS (62): It meets the requirements for the absence of Staphylococcus aureus and Pseudomonas aeruginosa,

7 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in collapsible tubes or tight containers.

USP REFERENCE STANDARDS (11)

USP Betamethasone Dipropionate RS

USP Clotrimazole RS

USP Clotrimazole Related Compound A RS

(o-Chlorophenyl)diphenylmethanol.

C₁₉H₁₅CIO             294.78