Marplan, Nardil, Ensam and Parnate are MAO inhibitors, according to Mayo Clinic. They are consumed orally. Selegiline is another MAOI. It is taken externally as a patch placed on the skin.
MAOIs were among the first antidepressants developed. They work by inhibiting monoamine oxidase, elevating levels of serotonin, dopamine, and norepinephrine in the brain, according to Medicine Net. MAOIs are also utilized to treat Parkinson's disease.
MAOIs are not commonly used due to their many side effects. They are typically used when other antidepressants are ineffective. Dry mouth, insomnia, headache, and diarrhea are common side effects of MAOs. Severe side effects requiring medical symptoms include low blood pressure and difficulty urinating, according to Mayo Clinic.