Urinary metabolism of chlorphenoxamine in man

After an oral dose of 40 mg of 4-chlorophenyl-methylbenzyloxy-N,N-dimethyl-ethylamine(chlorphe noxamine, Systral) urinary metabolism was studied by gas chromatography/mass spectrometry. Besides the unchanged drug, 8 metabolites and 7 artifacts and derivates could be identified. Metabolism is similar to that of the structurally related antihistaminic drugs diphenhydramine and doxylamine. The main metabolic pathways are: 1. N-demethylation, 2. oxidative desamination and formation of an alcohol and a carbonic acid derivative, 3. cleavage of the ether bond, and 4. hydroxylation of the phenyl ring. For determination of chlorphenoxamine in plasma an assay using gas chromatography was developed. Chlorphenoxamine plasma levels were beyond the limit of detection (10 ng/ml) 30, 60, 120, 240, 480, and 1200 min after oral intake.