Variable metabolism of pinacidil: lack of correlation with the debrisoquine and trimethylamine C- and N-oxidative polymorphisms.

1. The urinary excretion of pinacidil and its N-oxide in man was found to vary over a five-fold range. 2. Studies in individuals with inherited deficiencies for C-hydroxylation (debrisoquine type) and trimethylamine N-oxidation showed that the N-oxidation of pinacidil did not co-segregate with these oxidative polymorphisms. 3. It is concluded that the variable N-oxidation of pinacidil is most likely to be due to variations in the activity of the P-450 isozymes rather than in the microsomal flavoprotein containing mixed-function amine oxidase of Ziegler which is considered to be responsible for the N-oxidation of trimethylamine.