Clocortolone Pivalate Cream

» Clocortolone Pivalate Cream contains not less than 90.0 percent and not more than 110.0 percent of C27H36ClFO5 in a suitable cream base. It may contain suitable preservatives.

Packaging and storage— Preserve in collapsible tubes or in tight, light-resistant containers.

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USP Clocortolone Pivalate RS

Identification— Place a portion of Cream, equivalent to about 1 mg of clocortolone pivalate, in a suitable separator. Add 5 mL of water, and extract with 10 mL of chloroform. Evaporate the chloroform layer to dryness, and dissolve the residue in 2 mL of methanol. Apply 20 µL of this test solution and 20 µL of a Standard solution of USP Clocortolone Pivalate RS in chloroform containing about 0.5 mg per mL about 1.5 cm from the bottom of a suitable thin-layer chromatographic plate (see Chromatography

621

) coated with a 0.25-mm layer of chromatographic silica gel mixture. Allow the spots to dry, and develop the chromatogram in a solvent system consisting of cyclohexane and ethyl acetate (2:1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and allow the solvent to evaporate. Locate the spots on the plate by viewing under short-wavelength UV light: the RF value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.

Minimum fill

755

: meets the requirements.

791

: between 5.0 and 7.0, in a 1 in 10 aqueous dispersion.

Particle size determination— Place a small portion of Cream on a microscope slide, apply a cover slide, press slightly, and examine under 40× objective magnification using a suitable microscope equipped with polarized light. Scan the complete slide preparation, and record the size of the largest crystal found in reference to a calibrated grid: no particle in the Cream is greater than 50 microns when measured in the longitudinal axis.

Assay—

Standard preparation— Dissolve an accurately weighed quantity of USP Clocortolone Pivalate RS in methanol to obtain a solution having a known concentration of about 0.06 mg per mL.

Assay preparation— Using a plastic syringe equipped with a suitable cannula, transfer an accurately weighed quantity of Cream, equivalent to about 3 mg of clocortolone pivalate, to a 50-mL volumetric flask. Add about 25 mL of methanol, and warm the flask in a 60

water bath for about 10 minutes, with occasional swirling, to disperse the Cream. Cool to room temperature, dilute with methanol to volume, and mix. Allow any insoluble material to settle.

Procedure— Transfer 10.0 mL of the Standard preparation to a 25-mL volumetric flask. Transfer 10.0-mL portions of the Assay preparation into two separate 25-mL volumetric flasks labeled Assay preparation and Assay blank, respectively. Evaporate the contents of the three flasks with the aid of a stream of air or nitrogen to dryness. Transfer 20.0 mL of a solution containing 250 mg of isoniazid and 0.3 mL of hydrochloric acid in 500 mL of methanol to the flasks containing the Standard preparation, the Assay preparation, and a fourth 25-mL volumetric flask labeled Reagent blank. Pipet 20 mL of acidified methanol solution (0.3 mL of hydrochloric acid diluted with methanol to 500 mL) into the flask labeled Assay blank. Insert the stoppers securely in the flasks, and place in a water bath at 60

for 2.5 hours, occasionally swirling the contents of each flask. Cool the flasks to room temperature, dilute with the acidified methanol solution to volume, and mix. Centrifuge the Assay preparation at high speed for 10 minutes. Concomitantly determine the absorbances of the Standard preparation, the Assay preparation, the Assay blank, and the Reagent blank against acidified methanol solution as the solvent blank in 1-cm cells at the wavelength of maximum absorbance at about 390 nm, with a suitable spectrophotometer. Calculate the quantity, in mg, of C27H36ClFO5 in the portion of Cream taken by formula:

50C(AU / AS)

in which C is the concentration, in mg per mL, of USP Clocortolone Pivalate RS in the Standard preparation; AU is the absorbance of the Assay preparation, corrected for the Assay blank and the Reagent blank; and AS is the absorbance of the Standard preparation corrected for the Reagent blank.

Auxiliary Information— Please check for your question in the FAQs before contacting USP.

Topic/Question	Contact	Expert Committee
Monograph	Domenick Vicchio, Ph.D. Senior Scientific Liaison 1-301-998-6828	(SM42010) Monographs - Small Molecules 4
Reference Standards	RS Technical Services 1-301-816-8129 rstech@usp.org

USP35–NF30 Page 2717