Isocarboxazid, sold under the brand name Marplan among others, is a non-selective irreversible monoamine oxidase inhibitor (MAOI) of the hydrazine class. Along with phenelzine and tranylcypromine, it is one of the three classic irreversible, non-selective MAOIs used as antidepressants in modern psychiatric practice. Availability varies by country; in the United States, all three remain available for clinical use, though isocarboxazid is prescribed less often than phenelzine or tranylcypromine. Its lower use has been attributed in part to practical issues of affordability and availability, a smaller literature base, and the absence of an FDA-approved generic equivalent.
Isocarboxazid is used primarily in treatment-resistant depression. It has been used in various depressive subtypes, including atypical depression, melancholic depression, and endogenous depression. Evidence for Alzheimer's disease or other dementia-related disorders mainly concerns other MAO inhibitors, especially selegiline, rather than isocarboxazid specifically.
Adverse effects and interactions
Isocarboxazid and other classic MAOIs are prescribed less often than newer antidepressants, partly because they require attention to dietary tyramine and drug interactions, and partly because many clinicians are less familiar with their modern use. The Prescriber's Guide to classic MAO inhibitors was written for clinicians, including those not experienced with MAOI prescribing, and describes its purpose as improving knowledge and correcting misconceptions about these drugs. in certain patient populations and with certain interacting drugs or foods due to the risk of serious adverse reactions. Some notable contraindications and precautions include:
- Pheochromocytoma, because of the risk of severe hypertensive reactions.
- Significant liver disease; rare hepatotoxicity has been reported with isocarboxazid.