Scopoletin is a coumarin that can be isolated from plants of the genus Scopolia. It has been identified as a natural antifungal compound. Scopoletin was also demonstrated to be an MAO inhibitor capable of increasing dopamine levels in mice and is therefore of potential interest for developing treatments for neurodegenerative diseases.

Nialamide is a non-selective, irreversible monoamine oxidase inhibitor of the hydrazine class. It was previously used as an antidepressant (trade name Niamid) but was withdrawn by Pfizer in 1963 due to the risk of hepatotoxicity.

Iproniazid is a non-selective, irreversible monoamine oxidase inhibitor (MAO) of the hydrazine class. It was originally developed for the treatment of Tuberculosis, but in 1952, its antidepressant properties were discovered when researchers noted that patients given isoniazid became inappropriately happy. Iproniazid is no longer clinically prescribed and has been withdrawn due to incidences of hepatotoxicity.

Amezinium is a sympathomimetic used for its vasopressor effects in the treatment of hypotensive states. Amezinium inhibited monoamine oxidase (MAO) activity. Amezinium antagonized the response to tyramine and blocked neuronal uptake of noradrenaline. Side effects revealed are: palpitation, headache, nausea/vomiting, hot flashes, high blood pressure.

Caroxazone, 2-oxo-2H-1,3-benzoxazine-3(4H)-acetamide, was a psychotropic agent which in clinical studies was shown to possess a relevant antidepressant activity and was used to treat depression. This drug acts as a reversible inhibitor on both monoamine oxidases, MAO-A and MAO-B. Caroxazone is no longer marketed.

Budipine is an antiparkinsonian drug, which was developed by Byk Gulden (now Takeda) for the treatment of Parkinson's disease. The drug has multiple mechanisms of action: it was found to interfere with dopamine biosynthesis, mainly by inhibiting MAO-B enzyme and stimulating aromatic L-amino acid decarboxylase. Also the drug inhibits the dopamine re-uptake and has weak affinity to NMDA and muscarinic receptors. Budipine passes the blood-brain barrier, is metabolized by hydroxylation, and is excreted by both in urine and feces within 24 h.

Iproniazid is a non-selective, irreversible monoamine oxidase inhibitor (MAO) of the hydrazine class. It was originally developed for the treatment of Tuberculosis, but in 1952, its antidepressant properties were discovered when researchers noted that patients given isoniazid became inappropriately happy. Iproniazid is no longer clinically prescribed and has been withdrawn due to incidences of hepatotoxicity.

Amezinium is a sympathomimetic used for its vasopressor effects in the treatment of hypotensive states. Amezinium inhibited monoamine oxidase (MAO) activity. Amezinium antagonized the response to tyramine and blocked neuronal uptake of noradrenaline. Side effects revealed are: palpitation, headache, nausea/vomiting, hot flashes, high blood pressure.