Effect of prazosin on feline recurrent urethral obstruction

The aim of this study was to determine if male cats treated with 7 days of prazosin following relief of urethral obstruction (UO) experienced decreased rates of recurrent urethral obstruction (rUO) within 30 days vs those treated with 7 days of placebo.

All castrated male cats presenting for the first time with UO from May 2014 to August 2017 were eligible for enrollment. Exclusion criteria included the administration of medications or passage of a urinary catheter prior to referral, the presence of heart disease or hypertension requiring medication, prior treatment with glucocorticoids, non-steroidal anti-inflammatory medications, prazosin or phenoxybenzamine, or radiographic identification of cystoliths. Cats were treated with standardized anesthetic and analgesic protocols, standardized indwelling urinary catheter management, and were hospitalized for care. A random numbers table was generated prior to study initiation and cats were randomized to receive either prazosin (0.5 mg PO q12h for 7 days) or placebo in a blinded fashion. A 30-day follow-up with owners via telephone was performed to identify the rate of rUO. Cats that did not receive the full course of study medication were removed from the analysis. The study was unblinded at the end of data collection.

Eighty cats were enrolled and 65 cats completed the study; 12 were excluded because they did not receive the study medication. Sixteen of 65 cats experienced rUO (25%). Of the 16 cats experiencing rUO, five received placebo (n = 5/28 [18%]) and 11 received prazosin (n = 11/37 [30%]). Ten of the cats that experienced rUO reblocked while still hospitalized. There was no significant difference in frequency of rUO in cats treated with prazosin vs placebo (P = 0.27).

Prazosin administered at 0.5 mg PO q12h did not decrease the rate of rUO in this population of obstructed male cats vs placebo. These results further support evidence suggesting that prazosin may not be beneficial in prevention of feline rUO.