Alclometasone Dipropionate Ointment 

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

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

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1 DEFINITION 

Alclometasone Dipropionate Ointment contains NLT 90.0% and NMT 110.0% of the labeled amount of alclometasone dipropionate (C₂₈H₃₇ClO₇) in a suitable ointment base. 

2 IDENTIFICATION 

A. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, both relative to the internal standard, as obtained in the Assay. 

B. Thin-Layer Chromatographic Identification Test 〈201〉 

Standard solution: 0.25 mg/mL USP Alclometasone Dipropionate RS in methanol 

Sample solution: Place a quantity of Ointment, equivalent to 1.25 mg of alclometasone dipropionate, in a 50-mL centrifuge tube, add 10 mL of 2,2,4-trimethylpentane, insert a stopper securely into the tube, and disperse the specimen using a vortex mixer. Add 5.0 mL of a solution of methanol in water (45 in 50), insert the stopper securely, shake vigorously for 2 min, and centrifuge at 2500 rpm for 3 min. Remove the lower, aqueous alcohol phase, and transfer to a stoppered vial. 

2.1 Chromatographic system

(See Chromatography 〈621〉, Thin-Layer Chromatography.)

Adsorbent: 0.25-mm layer of chromatographic silica gel mixture

Application volume: 20 µL

Developing solvent system: Chloroform and acetone (7:1)

2.2 Analysis

Samples: Standard solution and Sample solution

Dry the applications with the aid of a stream of nitrogen, and develop the chromatograms in a saturated, unlined chromatographic chamber. When the solvent front has moved three-fourths of the length of the plate, remove the plate from the chamber, mark the solvent front, and allow the solvent to evaporate. Observe the plate under short-wavelength UV light.

Acceptance criteria: The R value of the principal spot obtained from the Sample solution corresponds to that of the Standard solution. F

3 ASSAY

Procedure

Buffer: 6.80 g/L of monobasic potassium phosphate (0.05 M)

Solution A: Dilute 450 mL of methanol with water to 500 mL.

Mobile phase: Methanol and Buffer (2:1)

Internal standard solution: 0.15 mg/mL of betamethasone dipropionate in Solution A

Standard stock solution: 0.1 mg/mL of USP Alclometasone Dipropionate RS in Solution A

Standard solution: 0.05 mg/mL of USP Alclometasone Dipropionate RS obtained by combining, in a small stoppered ask, 5.0 mL of Standard stock solution and 5.0 mL of Internal standard solution

Sample solution: Transfer a quantity of Ointment, equivalent to 0.5 mg of alclometasone dipropionate, to a 50-mL centrifuge tube, add 10 mL of 2,2,4-trimethylpentane, insert a stopper securely into the tube, and disperse the specimen using a vortex mixer. Add 5.0 mL of Internal standard solution and 5.0 mL of Solution A, insert the stopper securely, shake vigorously for 2 min, and centrifuge at 2500 rpm for 3 min. Remove the lower, aqueous alcohol phase, and transfer this Sample solution to a stoppered vial.

3.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 4-mm × 30-cm; packing L1

Flow rate: 1.2 mL/min

Injection volume: 20 µL

System suitability

Sample: Standard solution

[Note—The relative retention times for alclometasone dipropionate and betamethasone dipropionate are about 0.7 and 1.0, respectively.] Suitability requirements

Resolution: NLT 3.0 between the analyte and internal standard peaks

Relative standard deviation: NMT 2%

3.2 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of alclometasone dipropionate (C₂₈H₃₇ClO₇) in the portion of Ointment taken:

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

R_U = peak height ratio of alclometasone dipropionate to the internal standard from the Sample solution

R_S = peak height ratio of alclometasone dipropionate to the internal standard from the Standard solution

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

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

Acceptance criteria: 90.0%–110.0%

4 PERFORMANCE TESTS

Minimum Fill 〈755〉: Meets the requirements

5 SPECIFIC TESTS

Microbial Enumeration Tests 〈61〉andTests for Specified Microorganisms 〈62〉: Meets the requirements of the tests for absence of Staphylococcus aureus and Pseudomonas aeruginosa

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in collapsible tubes or tight containers, and store at controlled room temperature.

USP Reference Standards 〈11〉

USP Alclometasone Dipropionate RS