Psychiatry/Monoamine oxidase inhibitor

MAOIs

also: phenelzine · moclobemide · tranylcypromine · cheese reaction

Overview

Rarely-used antidepressants — the tyramine ("cheese") reaction and the serotonin-syndrome interactions are the exam points.

Mechanism

Inhibit monoamine oxidase → ↓breakdown of serotonin, noradrenaline and dopamine. Irreversible non-selective (phenelzine) vs reversible MAO-A (moclobemide).

Indications

Atypical / refractory depression (specialist)

The agents

Phenelzine / tranylcypromineirreversible

Dietary tyramine restriction; long washout.

Moclobemidereversible MAO-A (RIMA)

Less tyramine risk.

Adverse effects

Hypertensive ("cheese") crisis with tyramineserious

Aged cheese, cured meats, Marmite, wine — avoid.

Serotonin syndrome with serotonergicsserious

Postural hypotension, anticholinergic effectscommon

Cautions & contraindications

Tyramine-rich foodsall

Hypertensive crisis.

Concurrent SSRI/SNRI/TCA/triptans/opioids (esp. pethidine)all

Serotonin syndrome — observe washout periods when switching.

Interactions

Sympathomimetics, serotonergics, tyramine

Monitoring & kinetics

BP; dietary counselling

Oral. Washout needed when switching to/from other antidepressants.

Source: BNF — MAOIs