Inhibition of human brain type A and B monoamine oxidase by chloropromazine and metabolites

Chlorpromazine and a variety of its hydroxylated and N-demethylated catabolites were found to inhibit both the A and B forms of human brain monoamine oxidase (MAO). All the phenothiazine drugs tested, with the exception of chlorpromazine sulfoxide which did not affect MAO activity, inhibited the A form of MAO equal to or better than the type B form of the oxidase. Compared to the tricyclic antidepressant drugs, chlorpromazine was the most effective inhibitor of the type A species of MAO whereas the antidepressant drugs had higher affinities for the B form of MAO.