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Addressing Serotonin Syndrome in Cats

Clinician's Brief (Capsule)


|March 2014

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This retrospective study examined selective serotonin reuptake inhibitor (SSRI) toxicosis in cats. SSRIs prolong the effect of serotonin by inhibiting reuptake of the neurotransmitter in the synaptic cleft. In humans, SSRIs are used to treat anxiety, depression, and obsessive compulsive disorders. In veterinary medicine, they are used for behavior modification, including treatment of aggression and urine spraying. The database of an animal poison control center was reviewed, and 33 cases of SSRI ingestion by cats were identified. These 4 SSRIs were commonly ingested by cats were venlafaxine (Effexor) and fluoxetine (Prozac). Less commonly ingested SSRIs included citalopram (Celexa) and escitalopram (Lexapro). Of the cases reviewed, 8 (24%) became symptomatic. Signs in those 8 cats included sedation (n = 6), GI signs (n = 4), cardiovascular signs (n = 1), central nervous stimulation (n = 1), and hyperthermia (n = 1). Twenty of the cats received treatment, including supportive and symptomatic care. For the 16 cats treated as in-patients, mean hospitalization time was 14.6 ± 7.8 hours. All symptomatic cats had complete resolution of signs. The overall prognosis is excellent.


Cats are unique with respect to poisonings or overdoses. Poisonings reported to the Animal Poison Control Center involved only 13% cats compared to 76% dogs, and they primarily were <1 year of age.1 Cats are inquisitive and may voluntarily ingest toxic substances, especially plants. They are fastidious groomers and may ingest topically applied toxins. In addition, they may be purposefully or accidentally administered drugs by the client. SSRIs are increasingly used in humans and animals for behavior modification, so it is expected there would be an increase in exposure and reported toxicity. SSRIs can cause serotonin syndrome at therapeutic and toxic doses in humans, and this report described what to expect and how to handle SSRI exposure in cats. Fortunately, there are no reports of severe reactions or death in cats with witnessed ingestion of SSRIs in cases reported to the ASPCA. Reporting intoxications to poison control centers serves to increase understanding of reactions and therapeutic strategies and should be a standard of care.—Elke Rudloff, DVM, DACVECC


Selective serotonin reuptake inhibitor (SSRI) toxicosis in cats: 33 cases (2004-2010). Pugh CM, Sweeney JT, Bloch CP, et al. JVECC DOI: 10.1111/vec.12091.

1. An overview of trends in animal poisoning cases in the United States: 2002-2010. McClean MK, Hansen SR. Vet Clin North Am Small Anim Pract 42:219-228, 2012.

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