A dose-ranging study of the efficacy and safety of tamsulosin, the first prostate-selective alpha 1A-adrenoceptor antagonist, in patients with benign prostatic obstruction (symptomatic benign prostatic hyperplasia).

OBJECTIVE

To evaluate the efficacy and safety in a dose-ranging study of tamsulosin (once-daily) as a modified-release formulation compared with placebo in patients with lower urinary tract symptoms (LUTS) associated with benign prostatic obstruction (BPO), and to establish the optimum dosage for phase III clinical studies.

PATIENTS AND METHODS

Of 169 patients with LUTS associated with BPO enrolled in a 3 week placebo run-in period, 126 were subsequently randomized to receive placebo (28), or 0.2 mg (35), 0.4 mg (30), or 0.6 mg (33) of tamsulosin once daily for 4 weeks. Free-flow and pressure-flow measurements, and modified Boyarsky symptom scores were used to determine efficacy. Safety was evaluated by monitoring adverse events and vital signs (including 8 h after the first dose), and by laboratory determinations.

RESULTS

Tamsulosin 0.4 mg and 0.6 mg produced significantly greater improvements in maximum urinary flow rate (Qmax) (2.2 mL/s, 22.6%, and 1.8 mL/s, 20.2%, respectively) than did placebo (-0.1 mL/s, -0.9%). The results from the pressure-flow studies confirmed the results for Qmax in the free flow studies, with optimum and significant effects for tamsulosin 0.4 mg. This also applied for detrusor pressure at maximum flow, which decreased by 26.6 cmH2O (-28.2%) on 0.4 mg tamsulosin whereas it increased by 4.9 cm H2O (5.7%) on placebo. The greatest reductions in total symptom score were obtained with tamsulosin 0.4 mg and 0.6 mg (4.1, -28.7%, and 4.4 points, -28.2%, respectively) compared with reductions of 3.4 (-20.1%) in the tamsulosin (0.2 mg) and 2.9 points (-17.7%) in the placebo groups. The difference in effects on total symptom score between treatment groups was not statistically significant, which can be attributed to the small sample size. Tamsulosin was well tolerated; at least one adverse event was reported by 29%, 23%, 27% and 36% of patients in the placebo and tamsulosin 0.2 mg, 0.4 mg and 0.6 mg groups, respectively. There were no apparent tamsulosin dose-dependent changes in vital signs from baseline to the end of 4 weeks of randomized treatment. Tamsulosin caused no statistically significantly greater changes in blood pressure than placebo during the initial 8 h after the first dose. There were no clinically significant changes in laboratory variables.

CONCLUSION

Tamsulosin is well tolerated and effective in improving urinary flow and relieving LUTS associated with BPO. Optimal effects are achieved with tamsulosin 0.4 mg administered once daily.