Psychosis during Chronic Levodopa Therapy Triggered by the New Antidepressive Drug Mirtazapine

We report the case of a patient developing psychosis after the addition of mirtazapine, a novel antidepressant enhancing serotonergic neurotransmission, to a chronic levodopa regimen. There was complete and rapid recovery upon low-dose clozapine treatment. To our knowledge, this is the first published case of a mirtazapine-levodopa interaction and the second case report of a psychosis induced by a serotonergic antidepressant in a patient with Parkinson's disease (PD). This phenomenon might be due to a postsynaptic serotonin receptor supersensitization caused by low central serotonin levels in treated PD.