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

Apparatus 1: 100rpm.

Time: 45minutes.

Standard solution— Prepare as directed for Standard Preparationunder Assay for Steroids á351ñ,using USP Dexamethasone RS.

Procedure— Extract a filtered aliquot of Dissolution Medium,equivalent to about 200µg of dexamethasone,with three 15-mLportions of chloroform.Evaporate the combined chloroform extracts on a steam bath just to dryness,cool,and dissolve the residue in 20mLof alcohol.Proceed as directed for Procedureunder Assay for Steroids á351ñ,except to allow to stand in the dark for 45minutes.Calculate the portion,in mg,of C22H29FO5dissolved by the formula: in which Vis the volume,in mL,of the aliquot extracted with chloroform.

Tolerances— Not less than 70%(Q)of the labeled amount of C22H29FO5is dissolved in 45minutes.

Procedure for content uniformity—

Standard solution— Prepare as directed for Standard Preparationunder Assay for Steroids á351ñ,using USP Dexamethasone RS.

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

Procedure— Proceed as directed for Procedureunder Assay for Steroids á351ñ,except to allow to stand in the dark for 45minutes.Calculate the quantity,in mg,of total steroids,as C22H29FO5,in the Tablet by the formula: in which Vis the volume,in mL,of the aliquot taken to prepare the Test solution.

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

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

Assay preparation— Weigh and finely powder not fewer than 10Tablets.Weigh accurately a portion of the powder,equivalent to about 5mg of dexamethasone,transfer to a 50-mLvolumetric flask,and add 30mLof dilute methanol (1in 2).Sonicate the flask for about 2minutes,shake by mechanical means for 30minutes,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 5µLand 25µL)of the Assay preparationand the Standard preparationinto a high-pressure liquid chromatograph (see Chromatography á621ñ)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 preparationis about 0.6full scale.Typically,the apparatus is fitted with a 4.6-mm ×30-cm column packed with packing L1and is equipped with an UVdetector capable of monitoring absorption at 254nm 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 preparationand the Standard preparation.Calculate the quantity,in mg,of C22H29FO5in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Dexamethasone RSin the Standard preparation,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.