Effect of silodosin on specific urinary symptoms associated with benign prostatic hyperplasia: analysis of international prostate symptom scores in 2 phase III clinical studies

Marc C Gittelman¹, Leonard S Marks², Lawrence A Hill³, Weining Volinn³, Gary Hoel^3
1South Florida Medical Research, Aventura, Florida, USA; ²University of California at Los Angeles and Urological Sciences Research Foundation, Los Angeles, California, USA; ³Watson Laboratories, Salt Lake City, Utah, USA

Purpose: Pooled results from 2 randomized, placebo-controlled, US phase III studies (NCT00224107, NCT00224120) showed that silodosin, a uroselective α-blocker, significantly improved International Prostate Symptom Scores (IPSS) in men with symptomatic benign prostatic hyperplasia (BPH). This analysis evaluated the effect of silodosin on each symptom assessed by IPSS questionnaire.
Materials and methods: Study participants (N = 923) were men aged ≥50 years with IPSS ≥13 and Qmax 4–15 mL/s. They received silodosin 8 mg or placebo once daily for 12 weeks. Patient responses to 7 IPSS questions were collected at weeks 0 (baseline), 0.5, 1, 2, 4, and 12 and scored on a 6-point scale. Efficacy of silodosin versus placebo was assessed by analysis of covariance.
Results: For each symptom, the 2 treatment groups had similar mean baseline scores. Decrease in score from baseline (mean ± standard deviation) to last observation was significantly greater with silodosin than with placebo for all symptoms (P < 0.005); symptom improvement with silodosin (versus placebo) was greatest for weak stream (silodosin, -1.1 ± 1.4 versus placebo, -0.5 ± 1.2; P < 0.0001) and smallest for nocturia (silodosin, -0.6 ± 1.1 versus placebo, -0.4 ± 1.2; P = 0.0037). Compared with placebo, silodosin significantly improved nocturia within 1 week (silodosin, -0.5 ± 1.07 versus placebo, -0.3 ± 1.05; P = 0.009) and all other symptoms within 3 to 4 days (P < 0.01).
Conclusions: Silodosin significantly improved all BPH-associated symptoms assessed by IPSS questionnaire within the first week of treatment. All improvements were maintained over the 12-week study period.

Keywords: BPH, symptoms, rapid onset, silodosin, α_1A-adrenoceptor antagonist