Packaging and storage— Preserve in well-closed,light-resistant containers,at controlled room temperature.

USP Reference standards á11ñ— USP Chlorpromazine Hydrochloride RS.

Identification— Suppositories respond to Identificationtest Bunder Chlorpromazine.

Other alkylated phenothiazines— Transfer a portion of Suppositories,equivalent to 45mg of chlorpromazine,to a stoppered centrifuge tube,add 10mLof methanol,shake vigorously to disperse the solid,warming gently if necessary,and centrifuge.Proceed as directed in the test for Other alkylated phenothiazinesunder Chlorpromazine,beginning with “Dissolve a suitable quantity of USP Chlorpromazine Hydrochloride RS.”The area and intensity of any spot,other than the principal spot,from the solution from the Suppositories are not greater than those of the spot from the Diluted standard solution(0.5%).

Assay— Place not less than 10Suppositories in a 250-mLbeaker,reduce the mass to the consistency of a paste by crushing with a spatula,and mix.Weigh accurately a portion of the mass,equivalent to about 50mg of chlorpromazine,place in a beaker,and dissolve in about 40mLof ether.Transfer to a 250-mLseparator with the aid of three 25-mLportions of ether,and extract with four 75-mLportions of 0.1Nhydrochloric acid,collecting the aqueous extracts in a 500-mLvolumetric flask.Add 0.1Nhydrochloric acid to volume,and mix.Transfer 10.0mLof this solution to a 200-mLvolumetric flask,add 0.1Nhydrochloric acid to volume,and mix.Dissolve an accurately weighed quantity of USP Chlorpromazine Hydrochloride RSin 0.1Nhydrochloric acid,and dilute quantitatively and stepwise with the same solvent to obtain a Standard solution having a known concentration of about 5.5µg of chlorpromazine hydrochloride per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 254nm and at 277nm,with a suitable spectrophotometer,using 0.1Nhydrochloric acid as the blank.Calculate the quantity,in mg,of chlorpromazine (C17H19ClN2S)in the portion of Suppositories taken by the formula: in which 0.897is the ratio of the molecular weight of chlorpromazine to that of chlorpromazine hydrochloride,Cis the concentration,in µg per mL,of USP Chlorpromazine Hydrochloride RSin the Standard solution,and the parenthetic expressions are the differences in the absorbances of the two solutions at the wavelengths indicated by the subscripts,for the solution from the Suppositories (U)and the Standard solution (S),respectively.

Expert Committee:(PA3)Pharmaceutical Analysis 3

USP28–NF23Page 454

Phone Number:1-301-816-8330