Debrisoquin, a selective inhibitor of intraneuronal monoamine oxidase in man

Abstract

Indices of MAO activity were monitored during administration of debrisoquin to 4 patients with hypertension. That there was no inhibition of MAO was indicated by unaltered urinary tryptamine and tyramine excretion, no depression of intestinal mucosal MAO activity, and no decrease of intestinal inactivation of orally ingested tyramine. Inhibition of sympathetic neuronal MAO is suggested by increased sensitivity to intravenous tyramine with a slight increase in norepinephrine sensitivity, decreased urinary VMA, and increased NMN excretion. It is suggested that anatomic selectivity of enzyme inhibition is related to drug‐concentrating mechanisms in sympathetic neurons.