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α1-Adrenoceptor antagonists are the first-line treatment for men with lower urinary tract symptoms (LUTS) suggestive of bladder outlet obstruction (BOO) caused by benign prostatic hyperplasia (BPH). However, the lack of selectivity of some of these agents can cause reduced blood pressure and cardiovascular adverse events. Drugs that selectively target α1A-adrenoceptors—the predominant α1-adrenoceptor subtype in the bladder outflow tract—are thought to improve LUTS while minimizing adverse effects. Silodosin, a new α1A-adrenoceptor antagonist that has high uroselectivity in experimental animals, has now been studied for the first time in European men with LUTS and presumed BPH.

In a multicenter, international, placebo-controlled and active-controlled clinical study, men with LUTS (defined as an International Prostate Symptom Score [IPSS] ≥13) and BOO (peak maximum flow rate [Qmax] 4–15 ml/s) were randomly assigned to receive silodosin 8 mg (n = 381), tamsulosin 0.4 mg (n = 384) or placebo (n = 190) once daily for 12 weeks. Patients were assessed with the IPSS questionnaire and measurement of Qmax, systolic and diastolic blood pressure and heart rate at baseline and after 7, 14, 28, 56 and 84 days of treatment.

Compared to placebo, both active treatments were associated with significantly greater improvements in total IPSSs, IPSSs for storage and voiding, and quality of life. Increases in Qmax did not differ significantly between groups. Neither silodosin nor tamsulosin showed superiority over each other in terms of efficacy. Retrograde ejaculation was reported by more patients in the silodosin group (14.2%) compared to the tamsulosin (2.1%) and placebo (1.1%) groups. The frequency of headache, the next most-common adverse event, did not differ significantly between the three groups.

The authors conclude that silodosin is a safe and effective treatment for moderate-to-severe LUTS caused by BPH, and might be most beneficial in elderly patients in whom drug–drug interactions are more likely and cardiovascular adverse effects need to be avoided.