Dyskinesias associated with atomoxetine in combination with other psychoactive drugs.

Toxicity experience with atomoxetine, a selective norepinephrine reuptake inhibitor approved for Attention Deficit Hyperactivity Disorder (ADHD), is limited. We report two cases of neurologic complications requiring hospitalization in patients when atomoxetine was added to other psychoactive drugs. A 9-year-old taking clonidine and dextroamphetamine developed psychosis, abnormal involuntary movements, and insomnia. An 18-year-old also initiating venlafaxine developed facial tics, tremors, and speech disturbance. Acute symptoms did not respond to diphenhydramine in either case, but resolved after atomoxetine and other medications were discontinued. Possible explanations include atypical atomoxetine effect, excess atomoxetine or metabolites due to poor metabolizer status (CYP 2D6 polymorphism/deficiency), a drug-drug interaction leading to elevated drug levels or to excess synaptic norepinephrine or dopamine. Serotonin syndrome is a possibility in the second case, but not the first. Clinicians should be aware of emergent dyskinesias when combining atomoxetine with dopaminergic, noradrenergic, or serotonergic medications.