Dimenhydrinate Tablets
Action and use
Histamine H1 receptor antagonist; antihistamine.
Definition
Dimenhydrinate Tablets contain Dimenhydrinate.
Content of dimenhydrinate, C17H21NO,C7H7ClN4O2
95.0 to 105.0% of the stated amount.
Identification
Shake a quantity of the powdered tablets containing 0.1 g of Dimenhydrinate with 10 mL of a mixture of equal volumes of chloroform and ether for 5 minutes, filter and evaporate the filtrate to an oily residue on a water bath. Add 3 mL of ether to the residue and scratch the interface between the residue and the ether gently with a glass rod until crystals appear in the liquid. Transfer the suspension of crystalline material in ether to a watch glass, allow the solvent to evaporate in a current of air and dry the residue at 60°. The infrared absorption spectrum of the residue, Appendix II A, is concordant with the reference spectrum of dimenhydrinate (RS 104).
TEST
Theophylline and substances related to diphenhydramine
Carry out the method for thin-layer chromatography, Appendix III A, using the following solutions.
1 volume of 13.5m ammonia, 9 volumes of methanol and 90 volumes of dichloromethane.
In the first examination:
any spot corresponding to theophylline in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (3) (0.5%).
In the second examination:
any secondary spot in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (2) (1%).
Disregard any spot extending from the line of application to an Rf value of about 0.1.
Assay
Weigh and powder 20 tablets. Dissolve a quantity of the powder containing 0.1 g of Dimenhydrinate as completely as possible in 20 mL of water, add 10 mL of 5m ammonia, mix, extract with successive quantities of 15, 15, 15, 10 and 10 mL of ether and wash the combined extracts with 10 mL of water. Evaporate the ether, warm the residue with 10 mL of ethanol (96%) until dissolved, cool, add 50 mL of 0.01m hydrochloric acid VS and titrate the excess of acid with 0.01m sodium hydroxide VS using methyl red mixed solution as indicator. Each mL of 0.01m hydrochloric acid VS is equivalent to 4.700 mg of C17H21NO,C7H7ClN4O2.