Objective: To determine the effectiveness of a readily available selective serotonin reuptake inhibitor (SSRI), fluoxetine hydrochloride, on reducing problem urine spraying in cats.
Design: Randomized placebo-controlled double-blind clinical trial.
Animals: 17 neutered cats > 1 year old with objectionable urine spraying behavior. Procedure-Owners recorded urine-spraying events for 2 weeks (baseline). Cats that vertically marked a mean of > or = 3 times per week were treated for 8 weeks with fluoxetine or fish-flavored liquid placebo. If urine spraying was not reduced by 70% by weeks 4 through 5, the dosage was increased by 50% for weeks 7 and 8. After discontinuation of treatment at the end of 8 weeks, owners recorded daily urine marks for another 4 weeks.
Results: The mean (+/- SE) weekly rate of spraying episodes in treated cats was 8.6 (+/- 2.0) at baseline, decreased significantly by week 2 (1.7 +/- 0.6), and continued to decrease by weeks 7 and 8 (0.4 +/- 0.2). The mean weekly spraying rate of cats receiving placebo was 7.8 (+/- 1.5) at baseline, decreased only slightly during week 1 (5.5 +/- 1.8), and did not decline further. When treatment was discontinued after 8 weeks, the spraying rate of cats that had received treatment varied. The main adverse reaction to the drug was a reduction in food intake, which was observed in 4 of 9 treated cats.
Conclusions and clinical relevance: Administration of fluoxetine hydrochloride for treatment of urine spraying in cats can be expected to considerably reduce the rate of urine marking. The frequency of spraying before treatment is predictive of the spraying rate when the drug is discontinued.