Rabbit syndrome is a rare[1] form of extrapyramidal side effect of antipsychotic drugs in which perioral tremors occur at a rate of approximately 5 Hz. Rabbit syndrome is characterized by involuntary, fine, rhythmic motions of the mouth along a vertical plane, without involvement of the tongue,[2][3] and resembling the chewing movements of a rabbit.[4] It is usually seen after years of pharmacotherapy, and is more prominent with high potency drugs like haloperidol, fluphenazine, and pimozide. There is also a low incidence with thioridazine, clozapine, olanzapine, aripiprazole,[5] and low doses of risperidone.
Rabbit syndrome can be treated with anticholinergic drugs. It generally disappears within a few days of treatment but may re-emerge after anticholinergic treatment is stopped. Another treatment strategy is to switch the patient to an atypical antipsychotic with high anti-cholinergic properties.[3]
References
^Yassa, R; Lal, S (1986). "Prevalence of the rabbit syndrome". American Journal of Psychiatry. 143 (5): 656–7. doi:10.1176/ajp.143.5.656. PMID2870650.