Betamethasone Dipropionate Lotion

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 Lotion 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 lotion 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 150 µg/mL of betamethasone dipropionate, prepared as follows. Transfer a portion of Lotion, equivalent to 0.6 mg of betamethasone dipropionate, to a 50-mL vial; add 10 mL of 0.1 N hydrochloric acid; then add 4 mL of chloroform. Disperse on a vortex mixer for about 1 min, shake vigorously for 10 min, and centrifuge at 2000 rpm for about 5 min. Transfer the chloroform layer to a suitable vial.

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.

Internal standard solution: 0.9 mg/mL of USP Beclomethasone Dipropionate RS in chloroform

Standard stock solution A: 0.6 mg/mL of USP Betamethasone Dipropionate RS in chloroform

Standard stock solution B: 0.3 mg/mL of betamethasone dipropionate and 0.45 mg/mL of beclomethasone dipropionate, prepared by combining 5.0 mL each of Internal standard solution and Standard stock solution A

Standard solution: To 10.0 mL of 0.1 N hydrochloric acid in a capped 5-mL centrifuge tube, add 4.0 mL of Standard stock solution B. Cap the tube, and shake vigorously for about 2 min, or disperse on a vortex mixer for about 1 min. Centrifuge at 2500 rpm for about 3 min. Transfer the chloroform phase to a suitable vial. Evaporate the chloroform under a stream of nitrogen at a slightly elevated temperature to dryness. Cool the vial to room temperature, add 4.0 mL, of methanol, and swirl to dissolve the residue.

Sample solution: Nominally 0.23 mg/mL of betamethasone, prepared as follows. Transfer a portion of Lotion, equivalent to 1.2 mg of betamethasone dipropionate (0.93 mg of betamethasone), into a capped 50-ml centrifuge tube. Add 10.0 mL of 0.1 N hydrochloric acid, shake to disperse, then add 2.0 mL of Internal standard solution and 2.0 mL of chloroform. Cap, and shake vigorously for about 2 min, or disperse on a vortex mixer for about 1 min. Centrifuge at 2500 rpm for about 3 min. Transfer the chloroform phase to a suitable vial. Evaporate the chloroform under a stream of nitrogen at a slightly elevated temperature to dryness. Cool the vial to room temperature, add 4.0 mL of methanol, and swirl to dissolve the residue.

Chromatographic system

(See Chromatography (621), Systern 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 Lotion 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

4 SPECIFIC TESTS

MINIMUM FILL (755): Meets the requirements

5 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight containers. Store at 25°, excursions permitted between 15" and 30°. Protect from light and freezing.

USP REFERENCE STANDARDS (11)

USP Beclomethasone Digropionate RS

USP Betamethasone Dipropionate RS