Medium: dilute hydrochloric acid (1 in 100); 500 mL.

Apparatus 1: 100 rpm.

Time: 45 minutes.

Standard solution— Prepare as directed for Standard Preparation under Assay for Steroids 351, using USP Dexamethasone RS.

Procedure— Extract a filtered aliquot of Dissolution Medium, equivalent to about 200 µg of dexamethasone, with three 15-mL portions of chloroform. Evaporate the combined chloroform extracts on a steam bath just to dryness, cool, and dissolve the residue in 20 mL of alcohol. Proceed as directed for Procedure under Assay for Steroids 351, except to allow to stand in the dark for 45 minutes. Calculate the portion, in mg, of C22H29FO5 dissolved by the formula: in which V is the volume, in mL, of the aliquot extracted with chloroform.

Tolerances— Not less than 70% (Q) of the labeled amount of C22H29FO5 is dissolved in 45 minutes.

Procedure for content uniformity—

Standard solution— Prepare as directed for Standard Preparation under Assay for Steroids 351, using USP Dexamethasone RS.

Test solution— Place 1 Tablet in a separator with 15 mL of water, and swirl to disintegrate the Tablet completely. Extract with four 10-mL portions of chloroform, filtering each portion through chloroform-washed cotton into a 50-mL volumetric flask, add chloroform to volume, and mix. Pipet a volume of this solution, equivalent to about 200 µg of dexamethasone into a glass-stoppered, 50-mL conical flask, evaporate the chloroform on a steam bath just to dryness, cool, and dissolve the residue in 20.0 mL of alcohol. Use this where Assay Preparation is specified in the Procedure.

Procedure— Proceed as directed for Procedure under Assay for Steroids 351, except to allow to stand in the dark for 45 minutes. Calculate the quantity, in mg, of total steroids, as C22H29FO5, in the Tablet by the formula: in which V is the volume, in mL, of the aliquot taken to prepare the Test solution.

Mobile solvent— Prepare a suitable aqueous solution of acetonitrile, approximately 1 in 3, such that the retention time of dexamethasone is between 3 minutes and 6 minutes.

Standard preparation— Dissolve an accurately weighed quantity of USP Dexamethasone RS in dilute methanol (1 in 2) to obtain a solution having a known concentration of about 0.1 mg per mL.

Assay preparation— Weigh and finely powder not fewer than 10 Tablets. Weigh accurately a portion of the powder, equivalent to about 5 mg of dexamethasone, transfer to a 50-mL volumetric flask, and add 30 mL of dilute methanol (1 in 2). Sonicate the flask for about 2 minutes, shake by mechanical means for 30 minutes, and dilute with the same solvent to volume. Filter a portion of the mixture through a suitable filter to obtain a clear filtrate.

Procedure— Introduce equal volumes (between 5 µL and 25 µL) of the Assay preparation and the Standard preparation into a high-pressure liquid chromatograph (see Chromatography 621) operated at room temperature, by means of a loop injector, adjusting the specimen size and other operating parameters such that the peak obtained with the Standard preparation is about 0.6 full scale. Typically, the apparatus is fitted with a 4.6-mm × 30-cm column packed with packing L1 and is equipped with an UV detector capable of monitoring absorption at 254 nm and a suitable recorder. In a suitable chromatogram, the coefficient of variation for five replicate injections of a single specimen is not more than 3.0%. Measure the responses of the peaks, at identical retention times, obtained with the Assay preparation and the Standard preparation. Calculate the quantity, in mg, of C22H29FO5 in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Dexamethasone RS in the Standard preparation, and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.