Metabolism of monoamine oxidase inhibitors
by
Baker GB, Urichuk LJ, McKenna KF, Kennedy SH
Department of Psychiatry,
University of Alberta,
Edmonton, Canada.
Cell Mol Neurobiol 1999 Jun; 19(3):411-26

ABSTRACT

1. The principal routes of metabolism of the following monoamine oxidase inhibitors (MAOIs) are described: phenelzine, tranylcypromine, pargyline, deprenyl, moclobemide, and brofaromine. 2. Acetylation of phenelzine appears to be a minor metabolic pathway. Phenelzine is a substrate as well as an inhibitor of MAO, and major identified metabolites of phenelzine include phenylacetic acid and p-hydroxyphenylacetic acid. Phenelzine also elevates brain GABA levels, and as yet unidentified metabolites of phenelzine may be responsible for this effect. beta-Phenylethylamine is a metabolite of phenelzine, and there is indirect evidence that phenelzine may also be ring-hydroxylated and N-methylated. 3. Tranylcypromine is ring-hydroxylated and N-acetylated. There is considerable debate about whether or not it is metabolized to amphetamine, with most of studies in the literature indicating that this does not occur. 4. Pargyline and R(-)-deprenyl, both propargylamines, are N-demethylated and N-depropargylated to yield arylalkylamines (benzylamine, N-methylbenzylamine, and N-propargylbenzylamine in the case of pargyline and amphetamine, N-methylamphetamine and N-propargylamphetamine in the case of deprenyl). These metabolites may then undergo further metabolism, e.g., hydroxylation. 5. Moclobemide is biotransformed by C- and N-oxidation on the morpholine ring and by aromatic hydroxylation. An active metabolite of brofaromine is formed by O-demethylation. It has been proposed that another as yet unidentified active metabolite may also be formed in vivo. 6. Preliminary results indicate that several of the MAOIs mentioned above are substrates and/or inhibitors of various cytochrome P450 (CYP) enzymes, which may result in pharmacokinetic interactions with some coadministered drugs.

MAO
RIMAs
MAOIs
MAO(B)
Reward
Phenelzine
Befloxatone
Brofaromine
Moclobemide
Isocarboxazid
The MAOI Diet
Tranylcypromine
MAO interactions
Atypical depression
Drugs for depression
MAOIs, stress and aggression
Tobacco smoke and reversible MAO inhibition

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