Monoamine Oxidase Inhibitors: General Concepts


Although many different classes of monoamine oxidase inhibitors exist, the medicines most regularly linked in poisoning are the first antidepressant drugs: isocarboxazid, phenelzine, as well as tranylcypromine. Clorgiline is additionally connected with a comparable hazardous account. The third-generation medications, consisting of moclobemide, have a better safety and security profile.

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Monoamine oxidase is the enzyme in charge of the dismissal of biogenic amines like epinephrine, tyramine, norepinephrine, dopamine, as well as serotonin. Restraint of this enzyme ends in a rise in synaptic absorption of biogenic amines. A boost in norepinephrine as well as serotonin, particularly, is believed to be accountable for the state of mind elevation. MAOIs are structurally comparable to amphetamine. In overdose, a considerable quantity of neurotransmitters is released, leading to a sympathomimetic toxidrome. Phenelzine, as well as isocarboxazid, are likewise hydrazine derivatives as well as, in overdose, have been connected with the development of seizure activity. As natural chemicals become diminished, patients develop cardiac collapse, which is usually refractory to therapy. Given the fact that MAOIs affect a chemical path, there is often a significant delay in the advancement of toxicity after overdose, with a lot of situations occurring in a 24-hour period after intake, although there are cases of poisoning happening up to 32 hours after overdose. This impact may occur with seemingly little overdoses of five or six tablets.

Risk Variables

The timeless risk variables for developing toxicity consist of increasing a prescribed dosage or eating foods rich in tyramine, such as merlot or aged cheddar cheese. Medication interactions occur when a new antidepressant, an SSRI is introduced without an appropriate washout duration of numerous weeks after stopping the MAOI.


Clients need to be well informed on the risk connected with these drugs. The duration of action of these medications significantly outlives their half-lives; consequently, doctors should use a recommendation overview or consult a pharmacist before recommending a new medicine in addition to or as a replacement for the MAOI.

Associated Issues

  • MAOIs have been connected with extreme hypertensive dilemmas in the setting up of the coingestions of foods containing tyramine such as red wine or aged cheddar. Likewise, coingestion of indirect-acting sympathomimetics, which creates presynaptic launch of norepinephrine, may precipitate a hypertensive situation. Representatives consisted of in this category are dopamine, amphetamine-based drugs, as well as pseudoephedrine.
  • Serotonin disorder is additionally associated with the coingestion of SSRIs, meperidine, St. John’s wort, as well as dextromethorphan.