Serotonin Syndrome Following Combined Administration of Dopaminergic and Noradrenergic Agents in a Patient With Akinetic Mutism After Frontal Intracerebral Hemorrhage: A Case Report

Abstract

BACKGROUND: Serotonin syndrome (SS) is a potentially life-threatening condition that can be caused by use of proserotonergic drugs. Several studies have reported that combined administration of various medications may induce SS. We report a case of SS in a patient who was being treated with dopaminergic and noradrenergic drugs.

CASE PRESENTATION: A 55-year-old man with a right frontal intracerebral hemorrhage extending to the left cerebral hemisphere presented with clinical features of akinetic mutism. Three months after onset, dopaminergic (methylphenidate, levodopa/benserazide) and noradrenergic (atomoxetine) drugs were administered to enhance his cognitive function. His cognitive function gradually improved during 8 weeks of dose escalation. One day after the dose of atomoxetine was increased from 40 mg/d to 60 mg/d, the patient developed inducible clonus, rigidity, diarrhea, tachycardia, and hyperthermia, in keeping with a diagnosis of SS. The symptoms and signs suggestive of SS resolved on the day following cessation of all dopaminergic and noradrenergic drugs.

CONCLUSIONS: This case demonstrates that medications generally known as dopaminergic or noradrenergic agents could have serotonergic effects via a mechanism that is yet to be fully elucidated. The clinical manifestations of SS can be diverse, ranging from mild to severe and potentially fatal symptoms. When administering a combination of catecholaminergic agents, clinicians should carefully monitor the patient's neurologic status for unexpected adverse reactions.