Tamoxifen Citrate Tablets »Tamoxifen Citrate Tablets contain not less than 90.0percent and not more than 110.0percent of the labeled amount of tamoxifen (C26H29NO). Packaging and storage— Preserve in well-closed,light-resistant containers. USP Reference standards á11ñ USP Tamoxifen Citrate RS. Identification— A: The UVabsorption spectrum of the Test preparation,obtained as directed in the test for Content uniformity,exhibits maxima and minima at the same wavelengths as that of the Standard preparation,concomitantly measured. B: To 1Tablet contained in a 15-mLtube add 4mLof pyridine and 2mLof acetic anhydride:an immediate yellow color is produced on shaking.Then heat gently on a steam bath:a rose-pink to a deep red color develops,indicating the presence of citrate ion. Dissolution á711ñ Medium: 0.02Nhydrochloric acid;1000mL. Apparatus 1: 100rpm. Time: 30minutes. Procedure— Determine the amount of tamoxifen (C26H29NO)dissolved from UVabsorbances at the wavelength of maximum absorbance at about 275nm of filtered portions of the solution under test,suitably diluted with Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Tamoxifen Citrate RSin the same Medium. Tolerances— Not less than 75%(Q)of the labeled amount of C26H29NOis dissolved in 30minutes. Uniformity of dosage units á905ñ: meet the requirements. PROCEDURE FOR CONTENT UNIFORMITY Standard solution— Dissolve an accurately weighed quantity of USP Tamoxifen Citrate RSin methanol to obtain a solution having a known concentration of about 15µg per mL. Test solution— Place 1Tablet in a 100-mLvolumetric flask,and crush with a stirring rod.Add about 75mLof methanol,and shake for about 5minutes.Dilute with methanol to volume,mix,and filter the solution through paper.Pipet 10mLof the filtrate into a 100-mLvolumetric flask,dilute with methanol to volume,and mix. Procedure— Determine the absorbances of the Test solutionand the Standard solutionin 1-cm cells at the wavelength of maximum absorbance at about 275nm,with a suitable spectrophotometer,using methanol as the blank.Calculate the quantity,in mg,of tamoxifen (C26H29NO)in the Tablets taken by the formula: (371.51/563.64)(TC/D)(AU/AS), in which 371.51and 563.64are the molecular weights of tamoxifen and tamoxifen citrate,respectively;Tis the labeled quantity,in mg,of tamoxifen in the Tablet;Cis the concentration,in µg per mL,of USP Tamoxifen Citrate RSin the Standard solution;Dis the concentration,in µg per mL,of tamoxifen in the solution from the Tablet,based upon the labeled quantity per Tablet and the extent of dilution;and AUand ASare the absorbances of the Test solutionand the Standard solution,respectively. Assay— Mobile phase— Prepare a methanol solution containing,in each liter,320mLof water,2mLof glacial acetic acid,and 1.08g of sodium 1-octanesulfonate. Standard preparation— Dissolve a suitable quantity,accurately weighed,of USP Tamoxifen Citrate RSin Mobile phaseto obtain a solution having a known concentration of about 200µg per mL. Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 20mg of tamoxifen,to a stoppered,50-mLcentrifuge tube.Pipet 30mLof Mobile phaseinto the tube,and shake by mechanical means for not less than 15minutes.Centrifuge at about 1000rpm,pipet 5mLof the clear supernatant into a 25-mLvolumetric flask,dilute with Mobile phaseto volume,and mix. Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 4-mm ×30-cm column that contains packing L11.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak areas as directed for Procedure:the relative standard deviation for replicate injections is not more than 3.0%. Procedure— Separately inject equal volumes (about 25µL)of the Assay preparationand the Standard preparationinto the chromatograph by means of a suitable sampling valve,record the chromatograms,and measure the areas for the major peaks.Calculate the quantity,in mg,of tamoxifen (C26H29NO)in the portion of Tablets taken by the formula: 0.15C(371.51/563.64)(rU/rS), in which 371.51and 563.64are the molecular weights of tamoxifen and tamoxifen citrate,respectively;Cis the concentration,in µg per mL,of USP Tamoxifen Citrate RSin the Standard preparation;and rUand rSare the peak areas obtained from the Assay preparationand the Standard preparation,respectively. Auxiliary Information— Staff Liaison:Clydewyn M.Anthony,Ph.D.,Scientist Expert Committee:(PA1)Pharmaceutical Analysis 1 USP28–NF23Page 1847 Pharmacopeial Forum:Volume No.27(4)Page 2779 Phone Number:1-301-816-8139