For the past four decades, more than 30 agents or procedures have been recommended for managing spontaneously occurring feline lower urinary tract disease (FLUTD) of unknown cause, but few have been evaluated in controlled clinical trials. Amitriptyline hydrochloride (also used for humans with interstitial cystitis), a tricyclic antidepressant with many other qualities, has been among those advocated. Because of the rapid response of cats with severe recurrent idiopathic cystitis, short-term (7-day) treatment was selected for this study to determine if this drug was efficacious in cats with nonobstructive idiopathic FLUTD. Cats previously treated with mitriptyline were excluded from the study. Of 31 male and female cats with acute nonobstructive disease, 16 were treated with amitriptyline (5 mg/d) and 15 with placebo for 7 days. Cats were reexamined 1 month after treatment and by phone interview with the owners at 6, 12, and 24 months. Clinical signs resolved by day 8 in 8 of the treated and 10 of the control cats. There were no apparent differences in likelihood or rate of recovery from pollakiuria or hematuria between groups. Clinical signs recurred significantly faster and more frequently in treated cats than in the controls. After excluding recurrences within 21 days of treatment, risk for recurrence was similar in both groups. However, increased likelihood and rate of recovery from hematuria and decreased risk for recurrence were significant in relation to older age. Results suggest that short-term treatment has no benefit and may be associated with increased risk for recurrence.

COMMENTARY: Once again, the natural tendency of cats with FLUTD to spontaneously improve without treatment was evident in this study. Although amitriptyline demonstrated efficacy in ameliorating clinical signs of FLUTD in one long-term study, in this trial its well-known analgesic effects failed to reduce the duration of clinical signs. Amitriptyline may still be useful for long-term treatment of FLUTD in cats.

Randomized controlled trial of the efficacy of short-term amitriptyline administration for treatment of acute, nonobstructive, idiopathic lower urinary tract disease in cats. Kruger JM, Conway TS, Kaneene JB, et al. JAVMA 222:749-758, 2003.