Doxylamine metabolism in rat and monkey.

Metabolites of doxylamine obtained with rat-liver homogenate in vitro and from urine of Wistar rats and squirrel monkeys in vivo were examined. The metabolites were separated by g.l.c., h.p.l.c. and t.l.c., and tentatively identified through interpretation of their mass-spectrometric behaviour. N-Desmethyldoxylamine was identified in vitro while both N-desmethyl and N,N-didesmethyldoxylamine were detected in rat and monkey urine. The N-acetyl conjugates of N-desmethyl and N,N-didesmethyldoxylamine were tentatively identified both in rat urine and in vitro. Only the N-acetyl conjugate of N,N-didesmethyldoxylamine was detected in monkey urine. In addition, nine other metabolites were tentatively identified in rat urine: N,N-dimethyl-2-[1-(?-hydroxyphenyl)-1-(2-pyridyl)ethoxy]ethanamine; N-methyl-2-[1-(?-hydroxyphenyl)-1-(2-pyridyl)ethoxy]ethanamine; 1-phenyl-1-(2-pyridyl)ethanol; 1-(?-hydroxyphenyl)-1-(2-pyridyl)ethanol; 1-phenyl-1-(2-pyridyl)ethane; 1-(?-hydroxyphenyl)-1-(2-pyridyl)ethane; 2-phenyl-2-(2-pyridyl)ethanol; N,N-dimethyl-2-[1-phenyl-1-(2-pyridyl)-2-hydroxyethoxy]ethanamine; doxylamine pyridine N-oxide. The excretion of doxylamine aliphatic N-oxide in rat urine was confirmed by comparison with the authentic synthetic compound.