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Prazosin is an orally-active uroselective α-1-adrenergic antagonist which acts as a sympatholytic drug on vascular smooth muscle. It has very little α-2 antagonist activity[1].

Traditionally, the drug of choice for the treatment of functional urethral obstruction in dogs has been phenoxybenzamine, another α-adrenergic antagonist, but has been replaced by prazosin as a more selective α-1 antagonist.

This drug reduces intraurethral intraluminal pressure and is commonly used in cases of prostatic hyperplasia[2], acute urolithiasis[3] and ureterolithiasis[4].

Recommended dose rate in dogs is 20-50 μg/kg.


  1. Fischer JR et al (2003) Urethral pressure profile and hemodynamic effects of phenoxybenzamine and prazosin in non-sedated male beagle dogs. Can J Vet Res 67(1):30-38
  2. Breslin D et al (1993) Medical management of benign prostatic hyperplasia: A canine model comparing the in vivo efficacy of alpha-1 adrenergic antagonists in the prostate. J Urol 14:395–399
  3. Poirier M et al (1988) Effects of five alpha-blockers on the hypogastric nerve stimulation of the canine lower urinary tract. J Urol 140:165–167
  4. Noguchi Y et al (2008) In vivo study on the effects of alpha1-adrenoceptor antagonists on intraurethral pressure in the prostatic urethra and intraluminal pressure in the vas deferens in male dogs. Eur J Pharmacol 580(1-2):256-261