Mirtazapine induces REM sleep behavior disorder (RBD) in parkinsonism

Shortly after initiation of mirtazapine (a noradrenergic and serotonergic antidepressant) treatment in four patients with parkinsonism, the authors observed the appearance of REM sleep behavior disorder (RBD). In the two patients with severe motor symptoms, RBD was accompanied by hallucinations and confusion. These disturbances resolved with drug discontinuation, and remained resolved by 12- to 24-month follow-up, suggesting that RBD can be triggered by a drug lacking anticholinergic activity.