Objective: We present a case of refractory rabbit syndrome associated with the use of amitriptyline, a tricyclic antidepressant, highlighting both the diagnostic and therapeutic challenges that accompany this rare condition.

Background: Rabbit syndrome is a rare, drug-induced oral vertical dyskinesia characterized by rhythmic peri-oral movements. While it is typically linked to antipsychotics, it has also been associated with other pharmacological agents as well, including antidepressants [1].

Method: Case report

Results: A 55 year-old female with a history of anxiety and depression presented with abnormal oromandibular movements. Her symptoms were initially diagnosed as tardive dyskinesia (TD) secondary to amitriptyline use. Despite removing the offending medication, these movements persisted and even contributed to weight loss. She was started on valbenazine for her prior diagnosis of TD, but was discontinued as it worsened her symptoms. On exam, a rapid, rhythmic, side-to-side chin tremor without clear evidence of TD was seen. Trials of propranolol, carbidopa/levodopa, and benztropine showed minimal improvement. Both neurotoxin injections and trihexyphenidyl provided moderate, but incomplete, relief. Overall, her presentation was most consistent with rabbit syndrome, a drug-induced tremor, initially triggered by amitriptyline and subsequently exacerbated by weight loss, anxiety, and the introduction of valbenazine.

Conclusion: Rabbit syndrome is a rare, drug-induced oral vertical dyskinesia. Classically, it is characterized by rhythmic, peri-oral movements which resembles the chewing motion of a rabbit. Although it is typically associated with antipsychotics, it can also be triggered by other medications, including tricyclic antidepressants [1]. The condition is often challenging to diagnose due to its overlap with other drug-induced movement disorders, such as TD [1]. Management typically involves discontinuing the offending agent, but may require additional interventions such as anticholinergic medications or neurotoxin injections. In some cases, such as this one, incomplete resolution or persistent symptoms may occur despite these measures, complicating long-term management.

References: 1, Reyad, A. M. (2019). Rabbit syndrome: A rare, drug-induced movement disorder. Wolverhampton Open Repository.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/amitriptyline-induced-rabbit-syndrome-a-case-of-refractory-oral-vertical-dyskinesia/