Monoamine oxidase inhibitors

Monoamine oxidase inhibitors (MAOIs) are a class of medications that block the activity of monoamine oxidase enzymes (MAO-A and MAO-B), which are responsible for breaking down key neurotransmitters such as serotonin, norepinephrine, dopamine, and certain dietary amines like tyramine. By inhibiting these enzymes, MAOIs increase the availability of these neurotransmitters in the brain, which can improve mood and other aspects of brain function. Classic MAOIs such as phenelzine, tranylcypromine, and isocarboxazid are generally irreversible and non‑selective, while agents like selegiline and rasagiline are more selective for MAO‑B at typical doses. Clinically, MAOIs are primarily used as antidepressants, particularly in individuals with treatment‑resistant or atypical depression, and they are also used in certain anxiety disorders. Selective MAO‑B inhibitors are widely used in Parkinson’s disease to enhance dopaminergic signaling. Beyond their effects on mood and motor symptoms, MAOIs influence autonomic function, sleep, and energy levels, and have complex systemic effects because monoamine oxidase is expressed in many tissues throughout the body. Due to significant interaction risks with certain foods and medications, MAOIs are typically reserved for patients who have not responded adequately to safer or more convenient options. Strict dietary restrictions are required with classic MAOIs to avoid hypertensive crises precipitated by high‑tyramine foods. They also carry important interaction risks with serotonergic and sympathomimetic drugs, which can lead to serotonin syndrome or dangerous blood pressure elevations. For these reasons, MAOIs are prescription drugs and are not used as over‑the‑counter supplements for healthy individuals.