Alterations in the pattern of amine excretion in man produced by a monoamine oxidase inhibitor

The administration of monoamine oxidase inhibitors produces an increase in the urinary excretion of many amines for which efficient alternate routes of metabolism are not available. These include tryptamine, paratyramine, and a "metatyramine-like" substance. The inhibitors can therefore be used to detect previously unsuspected pathways of amino acid decarboxylation. The finding that the excretions of norepinephrine, epinephrine, 3,4-dihydroxyphenylethylamine, and possible serotonin are not appreciably affected are consistent with previous reports of the existence of alternative metabolic routes.