Monoamine Oxidase Inhibitors

Antidepressant and Antimanic Medications: Monoamine Oxidase Inhibitors

The MAOIs are some of the earliest developed antidepressant drugs. The initial enthusiasm that followed their discovery in the late 1950s was tempered by reports of serious side effects that relegated them to drugs of last resort. MAOIs have been associated with serious adverse events, including hypertensive crisis, lethal reactions with SSRIs, and delirium with meperidine, and less severe reactions reported with other opiate agonists such as morphine and partial agonists such as buprenorphine, butorphanol, and pentazocine. Hepatotoxicity, which was seen with the first MAOI drugs, appears to be very uncommon with the currently used MAOIs. Although they are free of anticholinergic side effects, these drugs commonly cause insomnia, daytime somnolence, clinically significant hypotension and orthostatic hypotension, anorgasmia, weight gain, myoclonus, and pedal edema. The hydrazine MAOIs (phenelzine and isocarboxazid) are associated with pyridoxine (B₆) deficiency in up to 7% of subjects.

MAOIs inhibit the primary enzyme responsible for degradation of monoamines, resulting in increased synaptic levels. Two forms of MAO exist in the CNS: type A (MAO-A) and type B (MAO-B). MAO-A metabolizes NE, serotonin, DA, and tyramine, whereas MAO-B metabolizes DA and tyramine but has no effect on NE or serotonin. Selective MAO-B inhibitors such as l-deprenyl, which is used in the treatment of Parkinson's disease, are relatively ineffective for depression.

Antidepressant and Antimanic Medications Introduction Diagnostic Indications and Contraindications

• Indications for Use of Antidepressant and Antimanic Medications
• Contraindications to Use of Antidepressant and Antimanic Medications
• General Treatment Guidelines Antidepressant Medications: Pharmacological Properties and Evidence for Acute-Phase Efficacy