INTRODUCTION
International continence society had divided OABS into storage, voiding and post micturition symptoms based on their aetiological factors in which overactive bladder symptoms (OABS) was defined as urgency with or without urge incontinence usually with increased frequency and nocturia without any proven infection or obvious pathology. OABS frequently overlap with storage LUTS induced by similar patho-physiological causes1 . In older men, BPH with LUTS and chronic obstruction induces changes in detrusor muscle culminating in detrusor over activity and inappropriate detrusor contractions during the storage phase of the micturition producing OABS2 . Around 50-75% of elderly male patients of BPH with LUTS appear to have predominant/coexisting OABS3 . Thus there exists a common unifying factor amongst BPH, LUTS and OABS with the common denominator being an inability to accommodate progressively increased bladder filling and sensation inducing secondary OABS.
Traditionally antimuscarinic drugs were the main stay of therapy for ‘BPH induced OABS’ albeit accompanied by bothersome adverse events like dry mouth, constipation and urinary retention leading to significant drug discontinuity4 . Mirabegron is a newer selective beta-3 agonist that has been tried in combination with α-1 blockers for alleviating ‘BPH induced OABS’ that act by relaxing the bladder detrusor in the storage phase thereby increasing its storage capacity and ameliorating OABS5, 6 . Some studies have documented the efficacy of Mirabegron as an add on (post alpha blocker therapy) managing residual storage LUTS in BPH patients with co-existing residual OABS8,9 . Herein we attempt to analyse the efficacy and safety of combination therapy (Mirabegron 50mg + tamsulosin0.4mg) in de novo select patients of BPH with predominantly coexisting OABS without prior alpha blockers run in therapy.