MAOIs

MAOIs, or monoamine oxidase inhibitors, are an older class of antidepressants that increase brain levels of monoamines by blocking the enzyme monoamine oxidase. By inhibiting MAO-A and MAO-B in the central nervous system, they raise serotonin, norepinephrine, and dopamine, which can relieve depressive symptoms. They are generally used for treatment-resistant depression and certain anxiety disorders after other agents have failed.

Common MAOIs include irreversible, nonselective inhibitors such as phenelzine, isocarboxazid, and tranylcypromine. Reversible inhibitors of MAO-A (RIMAs) such as moclobemide and selective MAO-B inhibitors like selegiline (at low doses) also exist; selegiline is primarily used for Parkinson disease, with limited antidepressant use. The choice of agent and monitoring depend on individual risk factors and coexisting conditions.

Dietary restrictions: nonselective MAOIs require avoidance of foods rich in tyramine (aged cheeses, cured meats, certain wines and beers) to prevent hypertensive crisis. Dietary restrictions are less strict with certain selective or reversible MAOIs, though interactions and hypertension risk can persist with some combinations.

Uses and interactions: MAOIs are generally considered after failure of other antidepressants, in atypical depression, or in some anxiety disorders. They require careful management of drug interactions, including avoidance of SSRIs, SNRIs, TCAs, meperidine, dextromethorphan, linezolid, and other serotonergic or sympathomimetic agents, due to risk of serotonin syndrome or hypertensive crises.

Adverse effects and considerations: common adverse effects include orthostatic hypotension, weight gain, sedation, edema, sexual dysfunction, and liver enzyme changes. Due to safety concerns and dietary needs, MAOIs are prescribed less frequently and usually under specialist supervision.