» Chlorpromazine Suppositories contain not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C17H19ClN2S.
Packaging and storage Preserve in well-closed, light-resistant containers, at controlled room temperature.
USP Reference standards 11
[NoteThroughout 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 Suppositories respond to Identification test B under Chlorpromazine.
Other alkylated phenothiazines Transfer a portion of Suppositories, equivalent to 45 mg of chlorpromazine, to a stoppered centrifuge tube, add 10 mL of methanol, shake vigorously to disperse the solid, warming gently if necessary, and centrifuge. Proceed as directed in the test for Other alkylated phenothiazines under 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 fewer than 10 Suppositories in a 250-mL beaker, 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 50 mg of chlorpromazine, place in a beaker, and dissolve in about 40 mL of ether. Transfer to a 250-mL separator with the aid of three 25-mL portions of ether, and extract with four 75-mL portions of 0.1 N hydrochloric acid, collecting the aqueous extracts in a 500-mL volumetric flask. Add 0.1 N hydrochloric acid to volume, and mix. Transfer 10.0 mL of this solution to a 200-mL volumetric flask, add 0.1 N hydrochloric acid to volume, and mix. Dissolve an accurately weighed quantity of USP Chlorpromazine Hydrochloride RS in 0.1 N hydrochloric acid, and dilute quantitatively and stepwise with the same solvent to obtain a Standard solution having a known concentration of about 5.5 µg of chlorpromazine hydrochloride per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 254 nm and at 277 nm, with a suitable spectrophotometer, using 0.1 N hydrochloric acid as the blank. Calculate the quantity, in mg, of chlorpromazine (C17H19ClN2S) in the portion of Suppositories taken by the formula:
10(0.897C)(A254 A277)U / (A254 A277)Sin which 0.897 is the ratio of the molecular weight of chlorpromazine to that of chlorpromazine hydrochloride; C is the concentration, in µg per mL, of USP Chlorpromazine Hydrochloride RS in 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.
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