Promethazine Hydrochloride Tablets

General Notices

Action and use

Histamine H1 receptor antagonist; antihistamine.

Definition

Promethazine Hydrochloride Tablets contain Promethazine Hydrochloride. They are coated.

The tablets comply with the requirements stated under Tablets and with the following requirements.

Content of promethazine hydrochloride, C17H20N2S,HCl

95.0 to 105.0% of the stated amount.

Identification

A. To a quantity of the powdered tablets containing 40 mg of Promethazine Hydrochloride add 10 mL of water and 2 mL of 1m sodium hydroxide, shake and extract with 15 mL of ether. Wash the ether with 5 mL of water, dry with anhydrous sodium sulfate, evaporate to dryness and dissolve the residue in 0.4 mL of chloroform. The infrared absorption spectrum of the resulting solution, Appendix II A, is concordant with the reference spectrum of promethazine (RS 297).
B. To a quantity of the powdered tablets containing 5 mg of Promethazine Hydrochloride add 5 mL of sulfuric acid and allow to stand for 5 minutes. A red colour is produced.
C. Dissolve a quantity of the powdered tablets containing 0.2 g of Promethazine Hydrochloride in 2 mL of water, filter, saturate with potassium carbonate sesquihydrate, extract with two 10 mL quantities of ether and evaporate the combined extracts to dryness. Dissolve the residue in 2 mL of methanol and pour into a solution of 0.4 g of picric acid in 10 mL of methanol at about 50°. Cool, scratch the side of the tube to induce crystallisation, allow to stand for 3 to 4 hours and filter. The melting point of the crystals, after washing with methanol and drying, is about 160°, Appendix V A.

Related substances

Carry out the test for related substances in phenothiazines, Appendix III A, using mobile phase B and applying separately to the plate 20 µL of each of the following freshly prepared solutions. For solution (1) extract a quantity of the powdered tablets containing 0.1 g of Promethazine Hydrochloride with 10 mL of a mixture of 95 volumes of methanol and 5 volumes of diethylamine and filter. Solution (2) contains 0.010% w/v of isopromethazine hydrochloride BPCRS in the same solvent. For solution (3) dilute 1 volume of solution (1) to 200 volumes with the same solvent. Any spot corresponding to isopromethazine in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (2) (1%) and any other secondary spot is not more intense than the spot in the chromatogram obtained with solution (3) (0.5%).

Assay

Carry out the following procedure protected from light. Weigh and powder 20 tablets. Triturate a quantity of the powder containing 50 mg of Promethazine Hydrochloride with 10 mL of 2m hydrochloric acid and add 200 mL of water. Shake for 15 minutes, add sufficient water to produce 500 mL and centrifuge about 50 mL of the mixture. To 5 mL of the clear, supernatant liquid add 10 mL of 0.1m hydrochloric acid and sufficient water to produce 100 mL. Measure the absorbance of the resulting solution at the maximum at 249 nm, Appendix II B. Calculate the content of C17H20N2S,HCl taking 910 as the value of A(1%, 1 cm) at the maximum at 249 nm.