Identification of Urinary and Biliary Metabolites of Alprenolol in the Rat

1. After oral administration of alprenolol to rat, 12 metabolites were isolated and characterized as trifiuoroacetyl, trimethylsilyl and n-butylboronate derivatives, using a g.l.c.-mass spectrometry-computer system. Fragmentation pathways of derivatives in the mass-spectrometric. analysis are discussed. 2. Metabolic reactions involved are oxidative degradation of the propanoliso-propylamine side-chain, aromatic hydroxylation, oxidation of the allyl group, and conjugation. A method for direct analysis of epoxide functions in the allyl group is described. 3. In comparison with metabolism of alprenolol in vitro, more polar metabolites are formed in vivo but the same principal metabolic pathways are valid. Structural features for biliary excretion are discussed.