Serotonin Syndrome and Drug Interactions, Hypertensive Complications, and, Adverse Effects of Monoamine Oxidase Inhibitors in Patients with Parkinson’s Disease

Monoamine oxidase (MAO), located in the outer mitochondrial membrane, is a critical enzyme in the metabolism of a number of neurotransmitters. Two isoforms of the enzyme exist, MAO-A and MAO-B [1]. These differ both in their tissue distribution and substrate selectivity. MAO-A is predominantly located in the periphery (including the gut) and preferentially catalyses the oxidation of 5-hydroxytyptamine (5-HT, serotonin) and norepinephrine [1]. MAO-B selectively metabolizes beta-phenylethylamine, while tyramine and dopamine are substrates for both types [1]. MAO inhibition, either non-specific or selective, increases the synaptic concentrations of the usually metabolized neurochemicals, providing symptomatic benefit in a variety of neurological and psychiatric disorders.