Tamsulosin is a subtype-selective α_1A- and α_1D-adrenoceptor antagonist. α₁-Receptors predominate in the prostate gland, prostatic capsule, prostatic urethra and bladder, and the relaxation of prostate and bladder smooth muscles is associated with improved maximal urine flow (Q_max) and alleviation of lower urinary tract symptoms (LUTS) in patients with benign prostatic hyperplasia (BPH).

Tamsulosin 0.4mg once daily in a modified-release formulation increased Q_max and improved symptom scores relative to baseline to a greater extent than placebo in 12- and 13-week double-blind, randomised, multicentre, clinical trials in patients with LUTS, with statistical significance between treatments for Q_max values in two of three published US and European studies. Tamsulosin is effective in patients with mild to severe LUTS associated with BPH, in patients with diabetes mellitus and in the elderly, and does not interfere with concomitant antihypertensive therapy. Pooled data based on patients receiving tamsulosin 0.4 or 0.8mg once daily indicate maintenance of efficacy for up to 6 years.

Tamsulosin 0.4mg once daily was of similar efficacy to alfuzosin 2.5mg three times daily, with less tendency to cause hypotensive effects, in a double-blind, randomised 12-week trial. Benefit of the drug has also been shown in patients with acute urinary retention or chronic abacterial prostatitis, those receiving high energy transurethral microwave thermotherapy, and in patients with prostate cancer with radiation-induced urethritis.

Dizziness and abnormal ejaculation are stated to be the most common adverse events, with asthenia, postural hypotension and palpitations being seen less frequently (1 to 2% incidence), in patients receiving tamsulosin 0.4mg once daily. Tamsulosin has not been associated with clinically significant changes in blood pressure in clinical trials.

Conclusion: The α_1A- and α_1D-adrenoceptor antagonist tamsulosin, given at a dosage of 0.4mg once daily in a modified-release formulation, is effective and well tolerated in the treatment of LUTS associated with BPH. Although the drug has been directly compared to date with one other agent only, data show overall that tamsulosin clearly offers advantages over other α₁-adrenoceptor antagonists in terms of the need for a single daily dose only, and its low potential for hypotensive effects or interference with concomitant antihypertensive therapy. Dosage titration at the start of treatment is not necessary. Tamsulosin has a rapid onset of action and is effective in patients with moderate or severe symptoms. The drug is therefore a valuable therapeutic option, with both demonstrated and potential advantages over older nonselective agents, in the management of patients with LUTS associated with BPH.

Tamsulosin is a subtype-selective α₁-adrenoceptor antagonist with a greater selectivity for prostatic tissues (where α_1A-adrenoceptors predominate) than for vascular tissues (α_1B-predominant). In contrast, other α₁-adrenoceptor antagonists (e.g. prazosin, terazosin, doxazosin and alfuzosin) show minimal subtype selectivity.

The efficacy of tamsulosin is attributable to the blockade of α_1A-adrenoceptors in the prostate gland. This inhibits smooth muscle contraction and improves dynamic voiding, which leads in turn to an improvement in the maximum urinary flow rate (Q_max). The blockade of α_1A- and α_1D-adrenoceptors in the bladder results in the inhibition of detrusor muscle contractions, which leads to reduced detrusor muscle instability and reduction of …