Studies on drug metabolism by use of isotopes XXIX—studies of the differences in biological fates of ephedrine isomers by use of a pseudo‐racemic mixture

The differences in metabolic fates of the optical isomers of ephedrine were investigated by use of a pseudo‐racemic mixture technique. In rats, the (—)‐isomer was more easily p ‐hydroxylated than the (+)‐isomer. A stereoselective reaction in the formation of the glucuronides of ephedrine, norephedrine and p ‐hydroxyephedrine was observed. The (—)‐isomers were more easily subjected to glucuronide formation than the (+)‐isomers. In human subjects, N ‐demethylation proved to be a steroselective reaction. It is also suspected that oxidative dealkylation of norephedrine is a stereoselective reaction.