Efficacy of fluoxetine for canine behavioral disorders

Abstract

The objectives of this retrospective descriptive study were to compare the efficacy of fluoxetine in conjunction with a behavior modification plan for the treatment of common canine behavioral disorders, and to compare the effects of other factors, including patient sex, fluoxetine dosage, and concurrent drug administration. Owners of all dogs prescribed fluoxetine through the Animal Behavior Clinic at the Cornell University Hospital for Animals in Ithaca, NY, between June 15th, 2012, and December 31st, 2016, were queried regarding their dogs’ behavior after prescription of fluoxetine. Behavioral diagnosis, fluoxetine dosage, concurrently administered psychoactive medications, sex, and response to fluoxetine for each dog were recorded. Of the 134 owners contacted, 93 responded. Eighty-eight dogs met inclusion criteria and were included in the study. Overall, 59% of owners reported that their dogs showed improvement, 32% reported no appreciable response, and 9% reported negative responses. Behavioral diagnoses were grouped into three categories: “Anxiety”, “Aggression”, and “Other” (which included compulsive/obsessive-compulsive behavior and self-mutilation). Most dogs in each category of diagnosis responded positively to treatment: 69% of dogs diagnosed with “Anxiety”, 55% of dogs diagnosed with “Aggression”, and 50% of dogs with a diagnosis of “Other”. A negative response to treatment was reported in 0% of dogs with a diagnosis of “Anxiety”, 13% of dogs diagnosed with “Aggression”, and 0% of dogs with a diagnosis of “Other”. More dogs prescribed fluoxetine at a daily dose of 0.5–0.99 mg/kg and 1.0–1.49 mg/kg responded positively to treatment (63% and 64%, respectively) than did dogs prescribed fluoxetine at 1.5–1.99 mg/kg daily (31%). Sixty-seven percent (N = 14/21) of dogs prescribed only trazodone in addition to fluoxetine and 63% (N = 5/8) of dogs prescribed only clonidine concurrently with fluoxetine responded positively to treatment, as compared with 59% (N = 23/39) of dogs prescribed fluoxetine as the sole agent. However, this difference was not significant. There was no significant effect of sex on treatment efficacy (Pearson chi square; [χ2 = 0.000; P = 0.999]). Sixty-eight percent (N = 19/28) of spayed females responded positively to treatment and 14% (N = 4/28) responded negatively, whereas 55% (N = 31/56) of castrated males responded positively and 9% (N = 5/56) responded negatively, a nonsignificant difference (Pearson chi square; (χ2 = 2.990; P = 0.224). Limitations of this study included its retrospective nature, number of owners who responded (N = 93; 66%) owner recall bias, and lack of control group (i.e., dogs with the same behavioral disorders that were not prescribed fluoxetine).