Thioridazine Hydrochloride Oral Solution »Thioridazine Hydrochloride Oral Solution contains not less than 90.0percent and not more than 110.0percent of the labeled amount of C21H26N2S2·HCl. Packaging and storage— Preserve in tight,light-resistant containers,at controlled room temperature. Labeling— Label it to indicate that it is to be diluted to appropriate strength with water or other suitable fluid prior to administration. USP Reference standards á11ñ USP Thioridazine Hydrochloride RS. NOTE—Throughout the following procedures,protect test or assay specimens,the Reference Standard,and solutions containing them,by conducting the procedures without delay,under subdued light,or using low-actinic glassware. Identification— Avolume of Oral Solution containing 50mg of thioridazine hydrochloride,diluted with water to 25mL,meets the requirements under Identification—Organic Nitrogenous Bases á181ñ,2mLof sodium bicarbonate solution (1in 12)being used in place of the 2mLof 1Nsodium hydroxide specified in the test. Alcohol content á611ñ: not more than 4.75%of C2H5OH. Assay— [NOTE—Conduct this procedure with a minimum of exposure to light.] Ammoniacal chloroform— Shake 125mLof chloroform with 5mLof ammonium hydroxide in a separator,slowly filter the bottom layer through filter paper containing anhydrous sodium sulfate,and discard the top layer. Standard preparation— Dissolve a suitable quantity of USP Thioridazine Hydrochloride RS,accurately weighed,in Ammoniacal chloroformto obtain a solution having a known concentration of about 6µg per mL. Assay preparation— Pipet a portion of Oral Solution,equivalent to about 120mg of thioridazine hydrochloride,into a separator containing 15mLof water.Render alkaline with ammonium hydroxide,and extract with three 25-mLportions of Ammoniacal chloroform.Filter the extracts through a pledget of glass wool into a 200-mLvolumetric flask.Rinse the filter,add chloroform to volume,and mix.Dilute 2.0mLof this solution with Ammoniacal chloroformto 200.0mL,and mix. Procedure— Concomitantly determine the absorbances of the Standard preparationand the Assay preparationin 1-cm cells at the wavelength of maximum absorbance at about 265nm,with a suitable spectrophotometer,using Ammoniacal chloroformas the blank.Calculate the quantity,in mg,of C21H26N2S2·HCl in each mLof the Oral Solution taken by the formula: 20(C/V)(AU/AS), in which Cis the concentration,in µg per mL,of USP Thioridazine Hydrochloride RSin the Standard preparation,Vis the volume,in mL,of Oral Solution taken,and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively. Auxiliary Information— Staff Liaison:Ravi Ravichandran,Ph.D.,Senior Scientist Expert Committee:(PA3)Pharmaceutical Analysis 3 USP28–NF23Page 1917 Phone Number:1-301-816-8330