Objectives. To evaluate the efficacy and safety of two once-daily doses of tamsulosin, the first selective alpha_1A-antagonist studied in clinical trials.

Methods. Patients with benign prostatic hyperplasia (BPH) were randomized to receive either tamsulosin (0.4 and 0.8 mg/day) or placebo (n = 756). Primary efficacy parameters were improvement in the total American Urological Association (AUA) symptom score and peak urinary flow (Qmax). Secondary efficacy parameters were improvement in measurements at individual double-blind visits corresponding to the primary efficacy parameters; percentage of patients with a 3-mL/s increase in Qmax; total AUA irritative, obstructive, and bother scores; individual AUA symptom scores; total, irritative, obstructive, and individual Boyarsky symptom scores; average urinary flow rate and other uroflowmetric parameters; and investigator’s global assessment.

Results. Statistically significant improvements in all efficacy parameters were observed in tamsulosin-treated compared with placebo-treated patients. Additionally, the 0.4-mg/day dose demonstrated a rapid onset of action (4 to 8 hours) based on Qmax after the first dose of double-blind medication. A review of the safety parameters demonstrated excellent tolerance at 1 week after the initial 0.4-mg/day dose and continued tolerance during the additional 12 weeks of 0.4- and 0.8-mg/day dosing. The incidence of positive orthostatic test results in the tamsulosin groups was comparable to that observed in the placebo group. Adverse events were comparable in the 0.4-mg/day tamsulosin and placebo groups and were somewhat higher in the 0.8-mg/day tamsulosin group.

Conclusions. Tamsulosin was effective, safe, and well tolerated in the target BPH population at both the 0.4- and 0.8-mg/day dose levels, without the blood pressure-lowering effects typical of nonselective alpha-adrenergic antagonists.