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)

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1 DEFINITION

Betamethasone Dipropionate Cream contains an amount of betamethasone dipropionate (C₂₈H₃₇FO₇) equivalent to NLT 90.0% and NMT 110.0% of the labeled amount of betamethasone (C₂₂H₂₉FO₅), in a suitable cream base.

2 IDENTIFICATION

A. THIN-LAYER CHROMATOGRAPHIC IDENTIFICATION TEST (201).

Standard solution: 150 µg/mL of USP Betamethasone Dipropionate RS in chloroform

Sample solution: Nominally equivalent to 150 µg/mL of betamethasone dipropionate, prepared as follows. Transfer 1.5 g of Cream to a glass-stoppered, 50-mL centrifuge tube. Add 15 mL of a methanol-hydrochloric acid solution prepared by mixing 1 volume of dilute hydrochloric acid (1 in 120) with 4 volumes of methanol, Shake to obtain a homogeneous mixture. Add 30 mL of solvent hexane, mix for 10 min, and centrifuge. Using a syringe, transfer the lower aqueous phase to a second centrifuge tube, and add 20 mL of water. Extract this aqueous mixture with chloroform by shaking, centrifuging, and removing the lower, chloroform phase with a syringe. Evaporate the chloroform on a steam bath with the aid of a stream of nitrogen to dryness, cool, and dissolve the residue in chloroform.

Chromatographic system

Application volume: 40 µL

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

Analysis

Samples: Standard solution and Sample solution Proceed as directed in the chapter.

Acceptance criteria: Meets the requirements

3 ASSAY

PROCEDURE

Mobile phase: Acetonitrile and water (1 in 2) such that the retention times for betamethasone dipropionate and beclomethasone dipropionate are 14 and 18 min, respectively. Degas by sonicating for 5-10 min. Do not leave the Mobile phase in the column overnight, but flush the system after use with water for 15 min, followed by methanol for 15 min.

Diluent: Acetic acid in methanol (1 in 1000)

Internal standard solution: 0.45 mg/mL of USP Beclomethasone Dipropionate RS in Diluent

Standard stock solution: 0.2 mg/mL of USP Betamethasone Dipropionate RS in Diluent

Standard solution: 0.133 mg/mL of USP Betamethasone Dipropionate RS and 0.15 mg/mL of USP Beclomethasone Dipropionate RS prepared by combining 10.0 mL of the Standard stock solution and 5.0 mL of the Internal standard solution

Sample solution: Nominally equivalent to 0.1 mg/mL of betamethasone, prepared as follows. Transfer a portion of Cream, equivalent to 2 mg of betamethasone dipropionate (1.6 mg of betamethasone), into a capped 50-mL centrifuge tube. Add 5.0 mL of Internal standard solution and 10.0 mL of Diluent, Heat in a water bath at 60^o, shaking intermittently, until the Cream melts. Remove from the bath, and shake vigorously until the Cream has resolidified. Repeat the heating and shaking. Freeze in an ice-methanol bath for 15 min, and centrifuge at 2500 rpm for 5 min. Use the supernatant.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 254 or 240 nm.

Column: 4-mm x 30-cm; packing L1

Injection volume: 5-25 µL

System suitability

Sample: Standard solution

Suitability requirements

Peak area ratios: The lowest and highest peak area ratios of three successive injections agree within 2.0%.

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of betamethasone (C₂₂H₂₉FO₅) in the portion of Cream taken:

Result = (R_u /R_s ) × (C_s /C_u ) × (M_r1 /M_r2 ) × 100

R_u = peak height ratio of betamethasone dipropionate to the internal standard from the Sample solution

R_s = peak height ratio of betamethasone dipropionate to the internal standard 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_r1 = molecular weight of betamethasone, 392.46

M_r2 = molecular weight of betamethasone dipropionate, 504.59

Acceptance criteria: 90.0%–110.0%

4 PERFORMANCE TESTS

Minimum Fill 〈755〉: Meets the requirements

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in collapsible tubes or tight containers. Store at 25°, excursions permitted between 15° and 30°. Protect from freezing.

USP Reference Standards 〈11〉

USP Beclomethasone Dipropionate RS

USP Betamethasone Dipropionate RS