Effects of Fluoxetine on Urine Spraying Behavior in Cats

Spraying is a common feline behavioral problem, most often in males, and it is one of the most frequent reasons why cats end up in pet shelters. To prevent this annoying behavior from happening, many owners should consider treatment. A study performed in 2001, at the University of California-Davis, showed the effectiveness of fluoxetine, a selective serotonin reuptake inhibitor (SSRI). In this randomized placebo-controlled double-blind clinical trial, 17 neutered cats > 1 year old with objectionable urine spraying behavior were included. 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 (1mg/kg PO Daily) 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. The mean 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. Therefore, this study showed that treatment with fluoxetine could considerably reduce urine spraying in cats by up to or greater than 90%, with only a few side effects with decreased appetite and lethargy being the most common.¹ An additional study performed in 2003 showed that transdermal application can also achieve therapeutic levels in felines; however, the relative bioavailability for TD administration is approximately only 10% of that for the oral route of administration.²

1. Pryor PA, Hart BL, Cliff KD, et al: Effects of a selective serotonin reuptake inhibitor on urine spraying behavior in cats. J Am Vet Med Assoc 219:1557-1561, 2001.
2. Ciribassi JL, Luescher A, Pasloske KS, Robertson-Plouch C, Zimmerman A, Kaloostian-Whittymore L. Comparative bioavailability of fluoxetine after transdermal and oral administration to healthy cats.Am J Vet Res. 2003;64:994–998.