Therapeutic Efficacy and Safety of Mirabegron , a β3-Adrenoceptor Agonist, Treatment on Patients With Overactive Bladder Syndrome in Taiwan - Comparison of Therapeutic Efficacy and Safety Between 25mg and 50mg

Overactive bladder syndrome (OAB) is defined as the symptom syndrome with frequency, and urgency with or without urgency incontinence. OAB affects more than 400 million people worldwide and has been estimated to affect around 16% of the adult population across Europe and the USA. In Asian countries, the prevalence of OAB has been reported to be 6% of men and women aged ≥18 years in China; 12.2% of men and women in Korea;12.4% of men and women aged ≥40 years in Japan; and 21 to 25% of women and 16.9% of community dwelling adults in Taiwan. Another study reported that the prevalence of OAB among adult men across 11 Asian countries (India, Indonesia, Malaysia, Pakistan, Philippines, Singapore, South Korea, Taiwan, China, Hong Kong and Thailand) was 29.9%.

Antimuscarinics are first line pharmacotherapy for OAB. However, some patients have a suboptimal response to antimuscarinics and some may experience adverse effects, such as dry mouth or constipation. Therefore, a high proportion of patients discontinue antimuscarinic therapy, with fewer than 25% remaining on treatment at 1 year. There is an unmet need to develop new drugs for OAB without the bothersome adverse effects of antimuscarinic agents.

β3-adrenergic receptors are known to promote urine storage in the bladder by inducing detrusor relaxation in animal and human bladders. In humans, the β3-adrenoceptor is the predominant β-receptor subtype in the urinary bladder. β3-adrenoceptor agonists relax the detrusor smooth muscle during the bladder storage phase and increase bladder capacity without accompanying changes in micturition pressure, residual volume or voiding contraction.

Mirabegron is the first β3-adrenoceptor agonist to have been approved for the treatment of OAB. Pooled safety data indicates that dry mouth, the chief cause of treatment discontinuation with antimuscarinic agents, occurs with low incidence with mirabegronc. Hence, mirabegron may be a valuable treatment option for patients with OAB.

Recent phase III trials have confirmed the efficacy and safety of mirabegron in the treatment of OAB in Europeans, Australians, North Americans, Japanese and Asians. Whether mirabegron 25mg or 50mg should be used as the first line treatment for OAB has not been determined yet. The dose effectiveness relationship between 25mg and 50mg mirabegron has also not been investigated yet. Hence, investigators have conducted this post-marketing study in order to evaluate the efficacy and safety between mirabegron 25mg and 50mg in Taiwanese people with symptoms of OAB.