Warfarin Sodium for Injection »Warfarin Sodium for Injection is a sterile,freeze-dried mixture of Warfarin Sodium and suitable added substances.It contains not less than 95.0percent and not more than 105.0percent of the labeled amount of warfarin sodium (C19H15NaO4).It may contain a suitable buffer. Packaging and storage— Preserve in light-resistant Containers for Sterile Solidsas described under Injections á1ñ. USP Reference standards á11ñ USP Endotoxin RS.USP Warfarin RS. Completeness of solution á641ñ A1.0-g portion dissolves in 10mLof carbon dioxide-free water to yield a clear solution. Constituted solution— At the time of use,it meets the requirements for Constituted Solutionsunder Injections á1ñ. Bacterial endotoxins á85ñ It contains not more than 24.0USP Endotoxin Units per mg of warfarin sodium. Water,Method Iá921ñ: not more than 4.5%. Other requirements— It responds to Identificationtests Aand B,and meets the requirements for pHand Heavy metalsunder Warfarin Sodium.It meets also the requirements for Sterility Tests á71ñ,Uniformity of Dosage Units á905ñ,and Labelingunder Injections á1ñ. Assay— pH7.4Buffer ,Mobile phase,and Chromatographic system—Prepare as directed in the Assayunder Warfarin Sodium. Internal standard solution— Dissolve propylparaben in a solvent consisting of a mixture of acetonitrile and glacial acetic acid (988:12)to obtain a solution having a concentration of about 1.0mg per mL. Standard preparation— Transfer about 94mg of USP Warfarin RS,accurately weighed,to a 100-mLvolumetric flask,and dissolve in 39.1mLof 0.1Nsodium hydroxide.Add 25.0mLof 0.2Mmonobasic potassium phosphate,dilute with water to volume,and mix.Pipet 5mLof this solution and 5mLof Internal standard solutioninto a 50-mLvolumetric flask,dilute with pH7.4Bufferto volume,and mix. Assay preparation— Dissolve the contents of not fewer than 10containers of Warfarin Sodium for Injection in a sufficient volume,accurately measured,of pH7.4bufferto obtain a solution containing about 1mg of warfarin sodium per mL.Pipet 5mLof the resulting solution and 5mLof Internal standard solutioninto a 50-mLvolumetric flask,dilute with pH7.4bufferto volume,and mix. Procedure— Proceed as directed for Procedurein the Assayunder Warfarin Sodium.Calculate the average quantity,in mg,of warfarin sodium (C19H15NaO4)in each container of Warfarin Sodium for Injection taken by the formula: 10(330.32/308.34)(VC/N)(RU/RS), in which 330.32and 308.34are the molecular weights of warfarin sodium and warfarin,respectively;Vis the volume,in mL,of the solution prepared from the contents of the 10or more containers;Cis the concentration,in mg per mL,of USP Warfarin RSin the Standard preparation;Nis the number of containers taken;and RUand RSare the peak response ratios of warfarin to propylparaben obtained from the Assay preparationand the Standard preparation,respectively. Auxiliary Information— Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist Expert Committee:(PA6)Pharmaceutical Analysis 6 USP28–NF23Page 2032 Phone Number:1-301-816-8389