Prazosin Should NOT Be Used for Feline Lower Urinary Tract Disease (FLUTD)
Prazosin administration is contraindicated in cats with FLUTD, as it significantly increases the rate of recurrent urethral obstruction and provides no clinical benefit for preventing lower urinary tract signs.
Evidence Against Prazosin Use
The most recent and highest quality evidence demonstrates clear harm from prazosin in feline urethral obstruction:
Prazosin increases recurrent urethral obstruction by nearly double: In a large observational study of 388 cats, 24% of prazosin-treated cats developed recurrent obstruction within 14 days compared to only 13% of untreated cats—a statistically significant increase in harm 1
No benefit for preventing recurrence: A prospective, double-blinded, placebo-controlled trial found no difference in recurrent obstruction rates between prazosin and placebo groups at hospital discharge (7% vs 5%), during the 1-month treatment period (15% vs 17%), or at 6 months (37% vs 31%) 2
No improvement in lower urinary tract signs: The same controlled trial found no difference in severity of dysuria, pollakiuria, hematuria, or stranguria at any follow-up period (weeks 1-4) between prazosin and placebo groups 2
Adverse Effects of Prazosin in Cats
Prazosin causes multiple side effects that compromise quality of life without providing therapeutic benefit:
- Lethargy, ptyalism (excessive salivation), diarrhea, anorexia, and malodorous stool were documented adverse effects in the controlled trial 2
Appropriate Management of FLUTD Instead
Since prazosin is contraindicated, focus on evidence-based interventions:
For urethral obstruction: Relieve the obstruction via urethral catheterization, provide fluid therapy to correct electrolyte abnormalities (particularly hyperkalemia), manage pain with opioids and NSAIDs, and monitor for post-obstructive diuresis 3
For feline idiopathic cystitis (FIC): Implement multimodal environmental modification (MEMO), ensure adequate water intake through wet food and multiple water sources, provide stress reduction, and consider analgesics during acute episodes 3
For urolithiasis: Pursue stone-specific dietary dissolution when possible (struvite stones), or surgical removal for stones that cannot be dissolved (calcium oxalate), followed by appropriate preventive diet 3
For bacterial urinary tract infection: Use culture-guided antibiotic therapy only when documented infection exists; do not treat asymptomatic bacteriuria 3
Critical Clinical Pitfall
Never prescribe prazosin routinely for cats with urethral obstruction or FLUTD—the alpha-1 blocker that works in human benign prostatic hyperplasia has no role in feline urinary disease and actively worsens outcomes 1. The anatomical and pathophysiological differences between human prostatic obstruction and feline urethral obstruction mean that extrapolation from human medicine is inappropriate and harmful 2, 1.
Human guidelines explicitly state insufficient data support prazosin use even for human lower urinary tract symptoms, making its use in cats—where it demonstrably increases harm—completely unjustified 4.