Antidepressants

Monoamine oxidase inhibitors (MAOIs) were the original antidepressants. MAOIs are very potent but more risky to use, particularly in older patients. MAOIs work by blocking the enzyme monoamine oxidase either reversibly or irreversibly. MAOIs that block the enzyme irreversibly are Iproniazid, Phenelzine, and Tranylcypromine. While taking these medications, patients have to avoid certain food products such as cheese (which contain higher levels of tyramine) as well as many over-the-counter cold medications. In combination with MAOIs these drug-food and drug-drug interactions may cause alarming increases in blood pressure and could be lethal. Since safer antidepressants are available now, these medications are seldom used.

Reversible inhibitors of monoamine oxidase, such as moclobemide and selegiline (only at lower doses) were introduced with the claim that they may not have the dangerous interactions like the irreversible MAOIs. Nonetheless, recent reports suggest that they should also be used very cautiously.