Letters to the Editor
Rabbit Syndrome Induced by Combined Lithium and Risperidone
Dear Editor: Rabbit syndrome, characterized by rapid, fine, rhythmic movements of the mouth along a vertical axis, is a rare extrapyramidal side effect (EPSE) of typical neuroleptics. We report the case of a woman with a history of bipolar disorder who exhibited rabbit syndrome as an acute extrapyramidal reaction after the addition of risperidone to lithium treatment.
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.
Mrs O was taking risperidone along with lithium; hence, lithium might have been a contributing factor or risk agent. Few reports suggest that lithium may potentate neuroleptic-related EPSEs or that it may reduce synthesis of dopamine (1,2). To our best knowledge, lithium-induced rabbit syndrome is nowhere reported. Surprisingly, Mrs O was previously exposed to lithium for 6 months but did not show any abnormal movements. It is also possible that lithium might have potentiated side effects even at dosages within the therapeutic range. In 3 recently published cases, all 3 patients had developed rabbit syndrome after continuing risperidone for approximately 4 months (3–5). However, in our case, rabbit syndrome appeared at week 4 of risperidone therapy. Mouth movement is typically rapid and rhythmic in rabbit syndrome, whereas irregular and slow movements are usually noticed in cases of tardive dyskinesia. Our patient did not exhibit abnormal movement until she was taking 4 mg of risperidone, which suggests it may be a dosage-related phenomenon.
Clinicians need to be aware of this rare, acute EPSE occurring with atypical antipsychotic drugs such as risperidone, especially in patients receiving concomitant lithium therapy.
References
1. Suchdeva PS. Lithium potentiation of neuroleptic-related extrapyramidal side effects [letter]. Am J Psychiatry 1975;132:536–8.
2. Friedman E, Gershon S. Side effects of lithium on brain dopamine. Nature 1973;243:520–1.
3. Levin T, Heresco-Levy U. Risperidone-induced rabbit syndrome: an unusual movement disorder caused by an atypical antipsychotics. Eur Neuropsychopharmacol 1999;9:137–9.
4. Schwartz M, Beny A, Sharf B. Risperidone-induced rabbit syndrome. Br J Psychiatry 1998;173: 276–8.
5. Hoys JS, Alexander B. Rabbit syndrome secondary to risperidone. Pharmacothrapy 2002;2:513–5.
DN Mendhekar, DPM, MD
New Delhi, India
|
