Procedure for content uniformity— Transfer 1 finely powdered Tablet to a 50-mL volumetric flask, add 25 mL of chloroform, and shake by mechanical means for 15 minutes. Dilute with chloroform to volume, mix, and filter, discarding the first 20 mL of the filtrate. Dilute a portion of the subsequent filtrate quantitatively and stepwise, if necessary, with chloroform to obtain a solution containing approximately 20 µg of paramethasone acetate per mL. Transfer 10.0 mL each of this solution and of a solution of USP Paramethasone Acetate RS in the same medium having a known concentration of about 20 µg per mL to separate 25-mL volumetric flasks, and transfer 10 mL of chloroform to a third flask to provide the blank. To each flask add 3.0 mL of a 1 in 4000 solution of blue tetrazolium in alcohol and 5.0 mL of a 1 in 20 solution of tetramethylammonium hydroxide TS in alcohol, mixing after each addition. Fifteen minutes, accurately timed, after the addition of the last reagent, add 1 mL of glacial acetic acid to each flask, dilute with chloroform to volume, and mix. Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 525 nm, with a suitable spectrophotometer, against the blank. Calculate the quantity, in mg, of C24H31FO6 in the Tablet taken by the formula: in which T is the labeled quantity, in mg, of paramethasone acetate in the Tablet, C is the concentration, in µg per mL, of USP Paramethasone Acetate RS in the Standard solution, D is the concentration, in µg per mL, of the solution from the Tablet, based upon the labeled quantity per Tablet and the extent of dilution, and AU and AS are the absorbances of the solution from the Tablet and the Standard solution, respectively.

Standard preparation— Transfer about 6 mg of USP Paramethasone Acetate RS, accurately weighed, to a separator containing 15 mL of water, and proceed as directed under Assay preparation, beginning with “add 3 drops of hydrochloric acid.”

Assay preparation— Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 6 mg of paramethasone acetate, to a separator containing 15 mL of water, add 3 drops of hydrochloric acid, and heat on a steam bath for 5 minutes, mixing frequently. Cool the separator to room temperature, add 4 drops of sodium hydroxide solution (1 in 2), and immediately extract with four 25-mL portions of chloroform. Filter the extracts through anhydrous sodium sulfate, collecting the extracts in a beaker. [Caution—Do not allow the filter paper to extend above the top of the funnel.] Rinse the filter with several small portions of chloroform, add the rinsings to the beaker, and evaporate the chloroform on a steam bath with the aid of a current of air until about 3 mL remains. Transfer the residual liquid, with the aid of several small portions of chloroform, to a glass-stoppered, 10-mL conical flask, and evaporate on a steam bath with the aid of a current of air to dryness. Add 2.0 mL of chloroform to the flask, insert the stopper, and mix to dissolve the residue.

Procedure— Concomitantly determine the absorbances of the solutions in 1-mm cells at the wavelength of maximum absorbance at 6.04 µm, with a suitable IR spectrophotometer, using chloroform as the blank. Calculate the quantity, in mg, of C24H31FO6 in the portion of Tablets taken by the formula: in which W is the weight, in mg, of USP Paramethasone Acetate RS used in preparing the Standard preparation, and AU and AS are the absorbances of the Assay preparation and the Standard preparation, respectively.