Lawrence A. Hill

Rapid Efficacy of the Highly Selective α1A-Adrenoceptor Antagonist Silodosin in Men With Signs and Symptoms of Benign Prostatic Hyperplasia: Pooled Results of 2 Phase 3 Studies

PURPOSE We evaluated the efficacy and safety of silodosin for treatment of benign prostatic hyperplasia symptoms in 2 randomized, placebo controlled, phase 3 studies. MATERIALS AND METHODS Men 50 years or older with an International Prostate Symptom Score of 13 or greater and peak urinary flow rate of 4 to 15 ml per second received placebo or 8 mg silodosin daily with breakfast for 12 weeks. The primary end point was International Prostate Symptom Score change from baseline to last observation. Change in peak urinary flow rate was a secondary end point. Differences in treatment efficacy were assessed by ANCOVA. RESULTS Of 923 patients (mean age 65 years) 466 received silodosin and 457 placebo. After 0.5 week (range 3 to 4 days) of treatment patients receiving silodosin vs placebo achieved significant improvement in total International Prostate Symptom Score (difference -1.9, p <0.0001) and irritative (-0.5, p = 0.0002) and obstructive (-1.4, p <0.0001) subscores. The mean +/- SD change from baseline in total International Prostate Symptom Score was -4.2 +/- 5.3 for silodosin vs -2.3 +/- 4.4 for placebo. Differences (silodosin vs placebo) in International Prostate Symptom Score and subscores increased by week 12 (p <0.0001). Mean change from baseline in peak urinary flow rate (ml per second) 2 to 6 hours after initial dose was greater (p <0.0001) with silodosin (2.8 +/- 3.4) than placebo (1.5 +/- 3.8). Differences remained significant (p <0.001) through week 12. The most common treatment emergent adverse event was (mostly mild) retrograde ejaculation (silodosin 28.1% of patients, placebo 0.9%). Few patients receiving silodosin (2.8%) discontinued because of retrograde ejaculation. Proportions of patients with treatment emergent orthostatic hypotension were similar for silodosin (2.6%) and placebo (1.5%). CONCLUSIONS Treatment with silodosin produced rapid improvement in urinary symptoms that was sustained for 12 weeks. Silodosin was well tolerated with a low incidence of orthostatic hypotension.

Silodosin in the treatment of the signs and symptoms of benign prostatic hyperplasia: a 9-month, open-label extension study.

OBJECTIVES To evaluate long-term safety of the highly selective alpha(1A)-adrenoceptor antagonist silodosin in men with signs and symptoms of benign prostatic hyperplasia (BPH). METHODS Patients enrolled in this open-label extension study had completed 1 of 2 identical double-blind, placebo-controlled 12-week studies of silodosin treatment for symptomatic BPH. For 40 weeks, patients received silodosin 8 mg once daily with breakfast. Adverse events (AEs) were recorded to evaluate safety. Change in International Prostate Symptom Score was a secondary variable. RESULTS Of the 661 participants, 435 (65.8%) completed the study; 431 patients (65.2%) experienced 924 AEs. No serious AEs that were considered drug-related by investigators occurred. AEs reported most often (percentage of patients) were retrograde ejaculation (20.9%), diarrhea (4.1%), and nasopharyngitis (3.6%). Orthostatic hypotension and dizziness occurred in 2.6% and 2.9% of patients, respectively. The percentage of patients with treatment-emergent AEs, stratified by preceding double-blind treatment (placebo or silodosin), was higher for de novo (previous treatment with placebo, 71.5%) than for continuing silodosin treatment (58.3%). More patients receiving de novo (7.5%) vs continuing treatment (1.9%) discontinued study participation because of retrograde ejaculation. Mean International Prostate Symptom Score change (standard deviation) from baseline to week 40 (observed cases) was -4.5 (6.7) for de novo treatment (P <.0001) and -1.6 (6.0) for continuing treatment (P <.01). CONCLUSIONS Silodosin was well tolerated by men with BPH-related symptoms and was associated with low incidences of dizziness and orthostatic hypotension. Discontinuation because of retrograde ejaculation was more common among patients receiving silodosin de novo than in those who continued silodosin treatment.

Silodosin for Men With Chronic Prostatitis/Chronic Pelvic Pain Syndrome: Results of a Phase II Multicenter, Double-Blind, Placebo Controlled Study

PURPOSE We evaluated the efficacy and safety of 2 doses of silodosin vs placebo in men with moderate to severe abacterial chronic prostatitis/chronic pelvic pain syndrome who had not been treated previously with α-blockers for chronic prostatitis/chronic pelvic pain syndrome. MATERIALS AND METHODS In this multicenter, randomized, double-blind, phase II study, men 18 years old or older with chronic prostatitis/chronic pelvic pain syndrome, a total National Institutes of Health Chronic Prostatitis Symptom Index score of 15 or greater and a National Institutes of Health Chronic Prostatitis Symptom Index pain score of 8 or greater received 4 or 8 mg silodosin, or placebo once daily for 12 weeks. The primary efficacy end point was change from baseline to week 12 in National Institutes of Health Chronic Prostatitis Symptom Index total score. RESULTS Of 151 patients (mean age 48 years) 52 received 4 mg silodosin, 45 received 8 mg silodosin and 54 received placebo. Silodosin 4 mg was associated with a significant decrease in total National Institutes of Health Chronic Prostatitis Symptom Index score (mean ± SD change -12.1 ± 9.3) vs placebo (-8.5 ± 7.2, p = 0.0224), including a decrease in urinary symptom (-2.2 ± 2.7, placebo -1.3 ± 3.0, p = 0.0102) and quality of life (-4.1 ± 3.1, placebo -2.7 ± 2.5, p = 0.0099) subscores. The 4 mg dose of silodosin also significantly increased Medical Outcomes Study Short Form 12 physical component scores (4.2 ± 8.1, placebo 1.7 ± 9.0, p = 0.0492). During global response assessment 56% of patients receiving 4 mg silodosin vs 29% receiving placebo reported moderate or marked improvement (p = 0.0069). Increasing the dose of silodosin to 8 mg resulted in no incremental treatment effects. CONCLUSIONS Silodosin 4 mg relieved symptoms and improved quality of life in men with chronic prostatitis/chronic pelvic pain syndrome but its efficacy requires confirmation in additional studies.

Lack of Pharmacodynamic Interaction of Silodosin, a Highly Selective α1a-Adrenoceptor Antagonist, With the Phosphodiesterase-5 Inhibitors Sildenafil and Tadalafil in Healthy Men

OBJECTIVES To evaluate the orthostatic effects and safety of coadministration of silodosin with the phosphodiesterase-5 inhibitors sildenafil and tadalafil. METHODS In this placebo-controlled, open-label crossover study, 22 healthy men aged 45-78 years received 8 mg silodosin for 21 days. On days 7, 14, and 21, subjects also received a single dose of sildenafil 100 mg, tadalafil 20 mg, or placebo in random sequence. Orthostatic tests were performed before (baseline) and 1-12 hours after single-dose treatment. A positive orthostatic test was defined as decrease in systolic blood pressure (SBP) >30 mm Hg, decrease in diastolic blood pressure (DBP) >20 mm Hg, increase in heart rate (HR) >20 bpm, or presence of orthostatic symptoms. Treatment effects were compared by analysis of covariance. RESULTS In comparison with placebo, sildenafil or tadalafil caused small but statistically significant reductions in blood pressure; however, no statistically significant orthostatic changes in SBP, DBP, or HR (P >.05) were caused. Time-matched maximum mean difference (95% confidence interval) vs placebo in 1-minute orthostatic change was -2.3 (-6.8-2.2) mm Hg for SBP, -2.2 (-5.6-1.2) mm Hg for DBP, and 1.7 (-1.5-4.9) bpm for HR. The number of postdose positive orthostatic tests was similar for all treatments (sildenafil, 57; tadalafil, 59; placebo, 53). Adverse events (in 7 subjects) were mild (26) or moderate (2). No orthostatic symptoms occurred. CONCLUSIONS Coadministration of silodosin and maximum therapeutic doses of sildenafil or tadalafil in healthy men caused no clinically important orthostatic changes in blood pressure or HR and no orthostatic symptoms.

Silodosin for the Treatment of Benign Prostatic Hyperplasia: Pharmacology and Cardiovascular Tolerability

Relief of benign prostatic hyperplasia (BPH)‐related lower urinary tract symptoms by α‐blockers (α‐adrenoceptor antagonists) is mediated primarily through the blockade of α1A‐receptors, leading to relaxation of smooth muscle in the prostate and bladder neck. Early α‐blockers that were nonselective for adrenoceptor subtypes have been associated with blood pressure‐related adverse effects, such as orthostatic hypotension, that may be attributed at least in part to the blockade of α1B‐adrenoceptors in arterial vessels. Silodosin, a novel α‐blocker with exceptionally high selectivity for α1A‐ versus α1B‐adrenoceptors, was recently approved in the United States for the treatment of urinary symptoms related to BPH. The unique receptor selectivity profile likely accounts for some of the desirable clinical features of the drug. Silodosin possesses an excellent cardiac‐ and blood pressure‐related safety profile, and data have demonstrated that it does not promote QT‐interval prolongation. Therapeutic doses of silodosin are safe for men with mild‐to‐moderate liver dysfunction; dosage adjustment is recommended in those with moderate renal impairment. The drug should not be taken with potent cytochrome P450 3A4 inhibitors. Silodosin may be especially beneficial in patients who need to maximize cardiovascular tolerability.

Effect of estimated prostate volume on silodosin-mediated improvements in the signs and symptoms of BPH: does prostate size matter?

Objective The uroselective α-blocker silodosin significantly improved International Prostate Symptom Score (IPSS) in two 12-week, double-blind (DB), placebo-controlled Phase III studies in men aged ≥ 50 years with symptoms of benign prostatic hyperplasia (BPH) and maintained symptom improvement during a 9-month open-label (OL) extension. This post-hoc analysis evaluated the effects of estimated prostate volume (EPV) on silodosin-mediated symptom improvement. Methods Patients were stratified by EPV (<30 mL or ≥ 30 mL) calculated from prostate-specific antigen (PSA) concentrations using a published algorithm. Group comparisons were done by analysis of covariance with last observations carried forward. Results Of 890 patients with PSA baseline data, 192 had EPV < 30 mL and 698 had EPV ≥ 30 mL. During DB treatment, silodosin was associated with significant symptom improvement (adjusted mean difference versus placebo) in men with EPV < 30 mL (−2.0; P = 0.038) and those with EPV ≥ 30 mL (−3.0; P < 0.0001). Among patients who received silodosin during DB treatment, changes from baseline in IPSS to the end of OL extension (mean ± standard deviation) were similar for EPV < 30 mL (n = 60, −7.0 ± 6.8) and EPV ≥ 30 mL (n = 242, −8.0 ± 7.1; P = 0.416). Also, among patients who received placebo as DB treatment, symptom improvement at the end of OL extension was similar for EPV < 30 mL (n = 62, −6.2 ± 8.1) and EPV ≥ 30 mL (n = 275, −6.7 ± 6.1; P = 0.339). Conclusion Silodosin effectively relieved BPH-related symptoms for up to 12 months, irrespective of prostate size, including in patients with enlarged prostates.

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

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.