MONOAMINE OXIDASE INHIBITORS

1. Examples of MAO-I: moclobemide, isocarboxacid

1. Binds to MAO-A and MAO-B
   • This increases the levels of noradrenaline, adrenaline and serotonin at the CNS synapse, by reducing their metabolism.
   • It also reduces the metabolism of tyramine (tyramine is important because it acts as a catecholamine releasing agent)
2. MAO-Is also resemble amphetamine and therefore may have CNS stimulating effects.

1. PO

1. Extensive first pass effect
2. Low bioavailability

1. Concurrent use of TCA and SSRI are absolute contra-indications.

1. SSRI/TCA
   • Life-threatening serotonin syndrome. Note that fluoxetine must be ceased 4 weeks prior to commencing a MAO-I and MAO-I must be ceased 2 weeks prior to commencing SSRI.
2. Sympathomimetics
   • Overall increased activity, e.g. ephedrine in over the counter cold preparations.
3. Foods rich in tyramine
   • Cheese, soy products, certain sausages (may get malignant hypertension)

1. Weight gain (serotonergic effect) and orthostatic hypotension
2. Amphetamine like effects – activation, insomnia and restlessness
3. Discontinuation syndrome may occur – psychosis, excitement

1. MAO-I overdose leads to increased adrenergic and serotonergic activity
   • Autonomic instability
   • Psychosis
   • Confusion, delirium

Treatment is with cardiac monitoring and good supportive care.