Central Nervous System Toxicity after Abrupt Monoamine Oxidase Inhibitor Switch: A Case Report

DESCRIPTION: There have been numerous case reports of adverse reactions involving monoamine oxidase inhibitors (MAOIs), including reactions that developed when one MAOI was substituted for another. Although most reports have usually described a switch from isocarboxazid or phenelzine to tranylcypromine, we report a case of acute central nervous system toxicity possibly associated with a switch from phenelzine to isocarboxazid. SYMPTOMATOLGY: Predominant symptoms included stuporous sensorium, hypertension, tachycardia, tremor, and urinary retention. Onset of symptoms began within 48 hours after the abrupt MAOI switch. CONCLUSIONS: Clinicians must allow a sufficient washout period before adding any agent that has a known potential to interact adversely with MAOIs. In addition, patients who are unusually sensitive to one type of MAOI may also be at increased risk for developing problems with a different MAOI secondary to unforeseen pharmacokinetic or pharmacodynamic effects, even at doses that are usually considered subtherapeutic.