Mechanism of Action of Tamsulosin in Benign Prostatic Hyperplasia

Pharmacological Effects

By blocking alpha-1A and alpha-1D adrenoceptors, tamsulosin inhibits alpha-1-adrenergic-mediated contraction of prostatic smooth muscle, contributing to bladder outlet obstruction in benign prostatic hyperplasia (BPH), with a significant impact on urinary flow and lower urinary tract symptoms 1, 2
Tamsulosin demonstrates greater selectivity for prostatic alpha-1 receptors, particularly alpha-1A, compared to vascular alpha-1 receptors, resulting in a lower probability of causing orthostatic hypotension compared to other alpha blockers like doxazosin and terazosin 2, 3

The main adverse effect specific to tamsulosin is ejaculatory dysfunction, which occurs in 4.5-14.0% of patients, a higher incidence compared to other alpha blockers 2
Tamsulosin use is associated with Intraoperative Floppy Iris Syndrome (IFIS) during cataract surgery, an important consideration for patients planning ophthalmic procedures 4

Dizziness occurs with higher frequency than placebo and may be mediated by the central nervous system, according to the American Urological Association, with a strength of evidence not specified 5

Tamsulosin demonstrates minimal impact on blood pressure compared to non-selective alpha-blockers, with dizziness, asthenia, and orthostatic hypotension incidence similar to placebo except at higher doses, as reported by the FDA, with a strength of evidence based on clinical trials 5