Clobetasone Ointment

Glucocorticoid.

Clobetasone Ointment contains Clobetasone Butyrate in a suitable basis.

The ointment complies with the requirements stated under Topical Semi-solid Preparations and with the following requirements.

90.0 to 110.0% of the stated amount.

A. Carry out the method for thin-layer chromatography, Appendix III A, using silica gel 60 GF₂₅₄ as the coating substance and a mixture of 5 volumes of absolute ethanol, 10 volumes of acetone and 100 volumes of chloroform as the mobile phase. Apply separately to the plate 10 µL of each of the following solutions. For solution (1) disperse a quantity of the ointment containing 0.5 mg of Clobetasone Butyrate in a mixture of 5 volumes of ethanol (80%) and 10 volumes of n-hexane, taking 15 mL of the solvent mixture for each g of ointment. Shake the mixture, allow to separate, filter the aqueous layer and add 10 mL of water and 1 g of sodium chloride for every 15 mL of the solvent mixture used. Extract the resulting aqueous solution with 5 mL of chloroform for each g of sodium chloride used and evaporate the chloroform layer to dryness in a current of dry nitrogen with gentle heating. Dissolve the residue in 0.5 mL of chloroform. Solution (2) contains 0.1% w/v of clobetasone butyrate BPCRS in chloroform. Solution (3) contains a mixture of equal volumes of solutions (1) and (2). After removal of the plate, allow it to dry in air and examine under ultraviolet light (254 nm). The principal spot in the chromatogram obtained with solution (1) corresponds to that in the chromatogram obtained with solution (2). The principal spot in the chromatogram obtained with solution (3) appears as a single compact spot.

B. In the Assay, the chromatogram obtained with solution (2) shows a peak with the same retention time as the peak due to clobetasone butyrate in the chromatogram obtained with solution (1).

caution Carry out the preparation of solutions (2) and (3) with full facial protection and wearing heat-resistant gloves.

Carry out the method for liquid chromatography, Appendix III D, using the following solutions. Solution (1) contains 0.004% w/v of clobetasone butyrate BPCRS and 0.0028% w/v of clobetasol propionate BPCRS (internal standard) in ethanol (50%). For solution (2) add 10 mL of absolute ethanol to a quantity of the ointment containing 1 mg of Clobetasone Butyrate. Stopper firmly using a plastic stopper and heat on a water-bath with intermittent shaking until the ointment is completely dispersed. Cool the contents in ice for 30 minutes, centrifuge and dilute 5 mL of the supernatant liquid to 10 mL with water. Prepare solution (3) in the same manner as solution (2) but adding 5 mL of absolute ethanol and 5 mL of a 0.014% w/v solution of the internal standard in absolute ethanol. Solutions (2) and (3) may assume a gel-like appearance.

The chromatographic procedure may be carried out using (a) a stainless steel column (10 cm × 4.6 mm) packed with octadecylsilyl silica gel for chromatography (5 µm) (Spherisorb ODS 1 is suitable) and maintained at 60°, (b) as the mobile phase with a flow rate of 2 mL per minute a mixture of 40 volumes of absolute ethanol and 60 volumes of water and (c) a detection wavelength of 241 nm. The proportions of the mobile phase may be adjusted to give a retention time for clobetasone butyrate of about 5.5 minutes.

Calculate the content of C₂₆H₃₂ClFO₅ in the ointment using peak areas and the declared content of C₂₆H₃₂ClFO₅ in clobetasone butyrate BPCRS.

Clobetasone Ointment should be stored at a temperature not exceeding 30°.