(dye'' men hye' dri nate).
Click to View Image
C17H21NO·C7H7ClN4O2 469.96

1H-Purine-2,6-dione, 8-chloro-3,7-dihydro-1,3-dimethyl-, compd. with 2-(diphenylmethoxy)-N,N-dimethylethanamine (1:1).
8-Chlorotheophylline, compound with 2-(diphenylmethoxy)-N,N-dimethylethylamine (1:1) [523-87-5].
» Dimenhydrinate contains not less than 53.0 percent and not more than 55.5 percent of diphenhydramine (C17H21NO), and not less than 44.0 percent and not more than 47.0 percent of 8-chlorotheophylline (C7H7ClN4O2), calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers.
USP Reference standards 11
USP Dimenhydrinate RS Click to View Structure
Identification— Infrared Absorption 197K.
Melting range 741: between 102 and 107.
Loss on drying 731 Dry it in vacuum over phosphorus pentoxide for 24 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.3%.
Bromide and iodide— Mix in a test tube 100 mg of Dimenhydrinate, 50 mg of sodium nitrite, and 10 mL of chloroform. Add 10 mL of 3 N hydrochloric acid, insert the stopper in the tube, and shake: the chloroform remains colorless.
Chloride— When the ammoniacal filtrate from the precipitation of silver chlorotheophylline in the Assay for 8-chlorotheophylline is acidified preparatory to titration, the solution shows not more than a faint opalescence.
Assay for diphenhydramine— Dissolve about 150 mg of Dimenhydrinate, accurately weighed, in 75 mL of glacial acetic acid, and titrate with 0.05 N perchloric acid VS, determining the endpoint potentiometrically. Perform a blank determination, and make any necessary correction. Each mL of 0.05 N perchloric acid is equivalent to 12.77 mg of diphenhydramine (C17H21NO).
Assay for 8-chlorotheophylline— Place about 800 mg of Dimenhydrinate, accurately weighed, in a 200-mL volumetric flask, add 50 mL of water, 3 mL of 6 N ammonium hydroxide, and 6 mL of ammonium nitrate solution (1 in 10), and warm the mixture on a steam bath for 5 minutes. Add 25.0 mL of 0.1 N silver nitrate VS, mix, and warm on a steam bath for 15 minutes with frequent shaking. Cool, dilute with water to volume, mix, and allow the precipitate to settle. Filter through a dry filter paper, discarding the first 20 mL of the filtrate. Pipet 100 mL of the filtrate into a 250-mL flask, acidify with nitric acid, and add an excess of 3 mL of the acid. Add 2 mL of ferric ammonium sulfate TS, and titrate the excess silver nitrate with 0.1 N ammonium thiocyanate VS. Each mL of 0.1 N silver nitrate is equivalent to 21.46 mg of C7H7ClN4O2.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Elena Gonikberg, Ph.D.
Principal Scientific Liaison
(SM32010) Monographs - Small Molecules 3
Reference Standards RS Technical Services
USP35–NF30 Page 2922
Pharmacopeial Forum: Volume No. 33(5) Page 907