Priapism--side-effect of prazosin in patients with renal failure.

Priapism developed during antihypertensive therapy with prazosin, 3-10 mg daily for 2-4 months, in two young men with severe renal failure. The cases are believed to be associated with alpha-adrenoceptor blocking and/or vasodilatory effects of the drug. Renal failure alone unlikely causes priapism, but may be an exposing factor for the episode.