Control of urine marking by use of long-term treatment with fluoxetine or clomipramine in cats

Objectives - To determine whether clomipramine differs from fluoxetine in reducing feline urine marking; whether reduction of marking continues in cats treated > 8 weeks; whether recurrence of marking, after abrupt drug withdrawal, is less in cats treated > 8 weeks; and whether cats that are successfully treated but resume marking after drug withdrawal can be successfully treated again with the same drug regimen. Design - Positive-controlled, double-masked clinical trial. Animals - 22 neutered cats (2 females, 20 males) ≥ 1 year old with objectionable urine marking. Procedure - Cats that marked vertically ≥ 3 times/wk were treated with fluoxetine (1 mg/kg [0.45 mg/lb], q 24 h, PO) or clomipramine (0.5 mg/kg [0.23 mg/lb], q 24 h, PO) for 16 weeks, and efficacy was compared. Recurrence of marking was determined after abrupt withdrawal of fluoxetine at 16 or 32 weeks. Reduction in marking in cats treated with fluoxetine for 8 weeks after returning to marking following drug withdrawal was compared with the initial 8 weeks of successful treatment. Results - Efficacy of fluoxetine and clomipramine was similar. Treatment > 8 weeks revealed increasing efficacy in reduction of marking. Return of marking after termination of fluoxetine administration occurred in most cats. Cats successfully treated initially with fluoxetine responded similarly to repeated treatment. Conclusions and Clinical Relevance - Clomipramine and fluoxetine were equivalent in treating urine marking. Longer treatment increased efficacy. Most cats return to marking after abrupt drug withdrawal. A second course of treatment can be expected to be as effective as the first.