From Dog

Tamsulosin is a urinary-selective α-1 antagonist.

Alpha-1-adrenoceptors are highly concentrated in the urethral smooth muscles, where their tone is maintained by stimulation of postjunctional a1-adrenoceptors through the release of noradrenaline from the adrenergic nerves.

Tamsulosin acts to inhibit smooth muscle contractility, with a 10 - 20 fold greater activity than phenoxybenzamine[1] and an equal activity with prazosin[2].

Tamsulosin results in reduction of intraurethral intraluminal pressure and is used for the treatment of prostatic hyperplasia, urolithiasis and ureterolithiasis[3]

This drug is used in human medicine for the relief of dysuria associate with prostatic disease, but in dogs does not appear as effective as silodosin for treating this condition[4].

Side-effects such as temporary ejaculate volume reduction may result in temporary infertility in some dogs[5].

Recommended dose in dogs is 30 - 100 μg/kg given two to three times daily[6].


  1. Taguchi K et al (1997) Effects of tamsulosin metabolites at alpha-1 adrenoceptor subtypes. J Pharmacol Exp Ther 280:1–5
  2. Ahmed H et al (2000) Contractile properties of urethral smooth muscles of young and aged female dogs: morphological and pharmacological aspects. Int J Urol 7(8):298-306
  3. Yamada S et al (1994) Comparative study on α1-adrenoceptor antagonist binding in human prostate and aorta. Clin Exp Pharmacol Physiol 21:405–411
  4. Kobayashi S et al (2009) Effects of silodosin and tamsulosin on the urethra and cardiovascular system in young and old dogs with benign prostatic hyperplasia. Eur J Pharmacol 613(1-3):135-140
  5. 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
  6. Sato S et al (2007) Relationship between the functional effect of tamsulosin and its concentration in lower urinary tract tissues in dogs. Biol Pharm Bull 30(3):481-486