Norethindrone and Ethinyl Estradiol Tablets
»Norethindrone and Ethinyl Estradiol Tablets contain not less than 90.0percent and not more than 110.0percent of the labeled amount of norethindrone (C20H26O2),and not less than 90.0percent and not more than 110.0percent of the labeled amount of ethinyl estradiol (C20H24O2).
Packaging and storage Preserve in well-closed containers.
Identification Crush 1Tablet in 1mLof alcohol in a 15-mLconical centrifuge tube,and warm to 50for 10minutes with gentle swirling.Cool,and centrifuge to obtain a clear solution.Apply 20µLof this test solution and 20µLof an alcohol solution containing,in each mL,about 1mg of USP Norethindrone RSand about 50µg of USP Ethinyl Estradiol RSat equidistant points along a line about 2.5cm from the bottom of a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel and previously activated by heating at 105for 30minutes.Develop the chromatogram in a mixture of benzene and ethyl acetate (4:1)in a suitable chamber,previously equilibrated with the solvent mixture,until the solvent front has moved about 10cm.Remove the plate,and air-dry.Spray the plate with sulfuric acid-methanol,prepared by cautiously adding 70mLof sulfuric acid in small increments to 30mLof methanol chilled in an ice-bath,and mixing:the spots from the test solution have the same RFvalues as the spots from USP Ethinyl Estradiol RS(about 0.7)and from USP Norethindrone RS(about 0.4).
Dissolution á711ñ [NOTEExercise care in filtering and handling solutions containing ethinyl estradiol to prevent adsorptive loss of the drug.Centrifugation may be used instead of filtration with nonadsorptive membrane filters.Withdraw dissolution aliquots with glass or polytef pipets or syringes that have been checked for adsorptive loss.Use glass dissolution vessels and polytef-coated or solid polytef paddles.]
Medium: 0.09%sodium dodecyl sulfate in 0.1Nhydrochloric acid;500mL.
Apparatus 2: 75rpm.
Determine the amounts of norethindrone (C20H26O2)and ethinyl estradiol (C20H24O2)dissolved,employing the following method.
Mobile phase Prepare a degassed and filtered mixture of 0.02MpH6.0phosphate buffer and acetonitrile (65:35).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Chromatographic system (see Chromatography á621ñ)The liquid chromatograph is equipped with a 200-nm detector,and a 5-mm ×8.3-cm column that contains 3-µm packing L1.The flow rate is about 1mLper minute.Chromatograph replicate injections of a filtered portion of a Standard solution of USP Norethindrone RSand USP Ethinyl Estradiol RSin Dissolution Mediumhaving concentrations similar to those expected in the solution under test.[NOTEAvolume of methanol not exceeding 4%of the total final volume of the Standard solution may be used in preparing the Standard solution.]Record the peak responses as directed under Procedure:the relative standard deviation is not more than 3.0%,the minimum number of theoretical plates for the ethinyl estradiol peak is not less than 7000,the resolution,R,for norethindrone and ethinyl estradiol is not less than 1.5,and the tailing factor does not exceed 2.0for either peak.
Procedure Separately inject equal volumes (about 100µL)of the Standard solution and a filtered portion of the solution under test into the chromatograph,record the chromatograms,and measure the responses for the major peaks.The relative retention times are about 0.9for norethindrone and 1.0for ethinyl estradiol.Calculate the quantities of norethindrone (C20H26O2)and ethinyl estradiol (C20H24O2)dissolved by comparison of the corresponding peak responses obtained from the Standard solution and the solution under test.
Tolerances Not less than 75%(Q)of each of the labeled amounts of C20H26O2and C20H24O2,respectively,are dissolved in 60minutes.
Uniformity of dosage units á905ñ: meet the requirements for Content Uniformitywith respect to norethindrone and to ethinyl estradiol.
Mobile phase Prepare a filtered and degassed mixture of acetonitrile and water (60:40).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Internal standard solution Transfer about 15mg of valerophenone into a 250-mLvolumetric flask,add 125mLof acetonitrile,dilute with water to volume,and mix.
Ethinyl estradiol standard stock solution Dissolve an accurately weighed quantity of USP Ethinyl Estradiol RSin acetonitrile,and dilute quantitatively and stepwise with acetonitrile to obtain a solution having a known concentration of about 0.09mg per mL.
Norethindrone standard stock solution Using an accurately weighed quantity of USP Norethindrone RS,prepare a solution in acetonitrile having a known concentration of about 1.25mg per mL.
Mixed standard preparation Transfer 5.0mLof Internal standard solutioninto a 100-mLvolumetric flask.Add accurately measured volumes of Ethinyl estradiol standard stock solutionand Norethindrone standard stock solutionso that the final known concentrations,in mg per mL,of the Reference Standards correspond numerically to about one-twentieth of the labeled amounts of the corresponding ingredients in the Tablets.Add (26-X)mLof acetonitrile,Xbeing the total volume of the standard stock solutiontaken.Dilute with a mixture of acetonitrile and water (45in 100)to volume,and mix.
Assay preparation Transfer 10Tablets to a 100-mLvolumetric flask,add 20mLof water,and shake by mechanical means until the tablets are completely disintegrated.Add 10.0mLof Internal standard solutionand 60mLof acetonitrile,and mix.Sonicate for about 2minutes.Dilute with acetonitrile to volume,and mix.Allow solid particles to settle,or centrifuge if necessary to obtain a slightly turbid solution.Dilute 5.0mLof this solution with a mixture of acetonitrile and water (45in 100)to 10.0mL,and mix.
Chromatographic system (see Chromatography á621ñ)The liquid chromatograph is equipped with a 200-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1.0mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed under Procedure:the column efficiency determined from the internal standard peak is not less than 8000theoretical plates,the resolution,R,between the norethindrone and ethinyl estradiol peaks is not less than 2.0,and the relative standard deviation for six replicate injections is not more than 2.0%(both peaks).
Procedure Separately inject equal volumes (about 25µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.The relative retention times are about 0.9for ethinyl estradiol and 1.0for norethindrone.Calculate the quantities,in mg,of norethindrone (C20H26O2)and ethinyl estradiol (C20H24O2)in each Tablet taken by the formula:
20C(RU/RS),in which Cis the concentration,in mg per mL,of the appropriate USP Reference Standard in the Mixed standard preparation,and RUand RSare the peak response ratios,at corresponding retention times,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