Rabbit Syndrome Induced by Combined Lithium and Risperidone

Case Report Mrs O, aged 42 years, presented with a third episode of bipolar illness (diagnosed according to DSM-IV criteria for mania) of 45 days duration; it was abrupt in onset, with the precipitating factor being malarial fever that was treated with tablet chloroquine for 4 days. Her history revealed that the first episode of mania occurred 4 years earlier and that she was treated with carbamazepine 600 mg daily for 6 months. Two years later, she had a second episode of mania, which was treated with carbamazepine 600 mg and lithium 900 mg daily for 1 year without any side effects. For the current episode, she was given lithium 800 mg daily; 2 weeks later, risperidone 2 mg daily was added. The risperidone was subsequently increased to 5 mg daily over a period of 2 weeks. At day 3 of risperidone 5-mg therapy, Mrs O exhibited the abrupt onset of abnormal perioral movements characterized by rapid, fine, rhythmic involuntary movement of her lips and jaw on a vertical axis, associated with akathisia and occasional synchronous lingual movement. Apart from akathisia and dyskinesia, no other EPSEs were seen. Her serum lithium level was 0.7 mEq/L. Her case was diagnosed as rabbit syndrome, and both the drugs were stopped. She scored 9 on the Abnormal Involuntary Movement scale. All her dyskinetic movements disappeared within 5 minutes of intravenous administration of 50 mg promethazine. Subsequently she was given olanzapine 10 mg and trihexiphenydyl 2 mg daily, along with the same dosage of lithium, without any recurrence of dyskinetic movements.