A Case of the Serotonin Syndrome Secondary to Phenelzine Monotherapy at Therapeutic Dosing

A 27-year-old Caucasian female with a history of depression was admitted to our local hospital with vague events that occurred a day before. This included an episode of dysarthria, and unsteadiness, followed by feeling generally unwell. Two weeks prior to presentation she was commenced on phenelzine. During clinical assessment she suddenly deteriorated with a dramatic fall in her conscious level. Moreover, she became hyperthermic, tachycardic, and diaphoretic, and developed increased tone in all muscles and ocular clonus. Rectal diazepam was administered but failed to control the symptoms. Consequently, she was transferred to the intensive care unit for intubation and muscle relaxants were commenced. She responded well and recovered next day without complications. Her symptoms and signs were consistent with the serotonin syndrome with phenelzine being the likely cause. To the best of our knowledge, this is the first reported case to associate the condition with phenelzine alone at therapeutic dose.