pharmacological actions
Last reviewed 01/2018
MAOI's inactivate the enzymes that oxidise noradrenaline, 5-HT, tyramine, and other amines which are widely distributed in the body as transmitters, or taken in food and drink, or as drugs. These drugs also inhibit hydroxylases in the liver, which in turn serves to inhibit the metabolism of substances such as barbiturates, tricyclic anti-depressants, phenytoin, alcohol and anti-parkisonian drugs.
The inhibition of monoamine oxidase occurs quickly, but on withdrawal it may take as long as two weeks before the enzyme is back to its previous level of activity.
MAOIs also have several autonomic side effects whose precise mechanisms are not clear: e.g. orthostatic hypotension, dry mouth, blurred vision, constipation, ankle oedema, delayed micturition and ejaculation.