Rabbit syndrome

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]


  1. ^ 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. PMID 2870650.
  2. ^ Villeneuve, A (1972). "The rabbit syndrome. A peculiar extrapyramidal reaction". Canadian Psychiatric Association Journal. 17 (2): Suppl 2:SS69–. doi:10.1177/07067437720176S213. PMID 5042912.
  3. ^ a b Catena Dell'Osso, Mario; Fagiolini, Andrea; Ducci, Francesca; Masalehdan, Azadeh; Ciapparelli, Antonio; Frank, Ellen (2007). "Newer antipsychotics and the rabbit syndrome". Clinical Practice and Epidemiology in Mental Health. 3: 6. doi:10.1186/1745-0179-3-6. PMC 1914060. PMID 17562001.
  4. ^ Schwartz, M; Hocherman, S (2004). "Antipsychotic-induced rabbit syndrome: Epidemiology, management and pathophysiology". CNS Drugs. 18 (4): 213–20. doi:10.2165/00023210-200418040-00002. PMID 15015902.
  5. ^ Gonidakis, F; Ploubidis, D; Papadimitriou, G (2008). "Aripiprazole-induced rabbit syndrome in a drug-naive schizophrenic patient". Schizophrenia Research. 103 (1–3): 341–2. doi:10.1016/j.schres.2008.01.008. PMID 18262773.