The purpose of this study is to investigate the safety and efficacy of combination therapy involving β3-adrenoceptor agonist, mirabegron, and α-blockers for the treatment of OAB symptoms in male patients with BPH.

Mirabegron (MyrbetriqTM, Astellas Pharma Inc.) is a drug that is approved by the FDA for the treatment of overactive bladder (OAB) with symptoms of urinary frequency, urgency and urgency incontinence. Multiple studies have shown that this drug also has the potential to improve patient tolerability, compliance and subsequent patient quality of life without inducing unfavourable adverse events commonly associated with antimuscarinic medications. These adverse events include, but are not limited to, dry mouth, constipation, confusion, and acute urinary retention (AUR).

Studies now have shown that mirabegron may also provide an effective treatment option for OAB in men with benign prostatic hyperplasia (BPH) without inducing the above mentioned adverse events. This study will look at the combination therapy of Mirabegron and Tamsulosin, versus Tamsulosin and placebo alone to prove that this treatment (Mirabegron and Tamsulosin) is effective for those men who suffer from both overactive bladder along with benign prostatic hyperplasia.

Inclusion Criteria:

• Male patients over the age of 50
• Clinical BPH on stable dose of alpha-blocker therapy for more than 1 month
• OAB symptoms (frequency, urgency, nocturia, urgency incontinence)

Exclusion Criteria:

• Post-void residual (PVR) > 200mL
• Active, culture-proven urinary tract infection
• Acute/chronic prostatitis
• Previous lower urinary tract malignancy (i.e. bladder, prostate malignancy)
• History of cystolithiasis
• Previous pelvic surgery (i.e. prostatectomy, cystectomy, recent pelvic/endourologic instrumentation including cystoscopy, nephroscopy, ureteral stent insertion, Transrectal Ultrasound (TRUS) biopsy)
• Previous pelvic radiation