Monoamine Oxidase Inhibitors; Reversible Inhibitors of Monoamine Oxidase

MAOIs are a broad class of psychoactive medications that affect the metabolism of multiple neurotransmitters.

MAOIs are indicated for many psychiatric conditions including but not limited to atypical depression, refractory depression, depression with prominent anxiety, low psychomotor activity, and severe phobias.

Other indications include Parkinson disease, narcolepsy, and intractable headache.

Risks result from accumulation of physiologically active neurotransmitters because of decreased levels of MAO. Best understood as either serotonergic or catecholic.

Hypertensive crises arise because of excess levels of tyramine from food or norepinephrine with vasoactive drugs. Manifests as dramatically increased sensitivity to adrenergic drugs, especially indirect-acting catecholamine agonists such as ephedrine.

Serotonin syndrome (central serotonergic hyperactivity) arises because of impaired metabolism and dramatic increase in concentration of serotonin. In pts on chronic MAOI therapy this concentration rarely rises with administration of anesthetic medications with serotonergic effects including but not limited to fentanyl and methadone.