Prazosin administration increases the rate of recurrent urethral obstruction in cats: 388 cases.

To determine if prazosin administration decreased the rate of recurrent urethral obstruction (rUO) before hospital discharge and within 14 days. 388 cats with urethral obstruction. Veterinarians who either always or never prescribed prazosin (generally, 0.5 to 1 mg, PO, q 12 h for 14 days) were recruited to complete observational surveys. Patient data and characteristics of relieving the obstruction, including perception of a gritty feel within urethra or difficulty unobstructing the cat, were recorded. The rate of development of rUO before hospital discharge and by day 14 was compared between cats that received or did not receive prazosin with the Fisher exact test. Other variables were similarly compared between cats with and without rUO. 302 (78%) cats received prazosin, while 86 (22%) did not. There was no association between prazosin administration and risk of rUO prior to discharge, with 34 of 302 (11.3%) cats receiving prazosin and 5 or 86 (5.8%) not receiving prazosin developing rUO. Within 14 days, a significantly higher proportion of prazosin-treated cats (73/302 [24%]) developed an rUO, compared with the proportion of non-prazosin-treated cats (and 11/86 [13%]). The perception of a "gritty feeling urethra" or difficulty of performing the catheterization was associated with increased risk of rUO. Prazosin administration increased the likelihood of rUO by 14 days; ongoing investigation of other therapies to decrease rUO in cats is warranted. Without specific indications, the use of prazosin for the prevention of rUO should be discouraged.