β3-Adrenoceptor agonist effects on the urinary bladder beyond detrusor relaxation

Abstract

Aims β3-Adrenoceptor agonists such as mirabegron or vibegron reach pharmacokinetic steady-state within a few days. However, maximum improvements in symptoms of the overactive bladder syndrome are reached at time points later than 4 weeks, that is, detrusor smooth muscle relaxation cannot fully explain clinical effects. Therefore, we review mechanistic studies that have administered such drugs for longer periods of time. Methods Narrative review. Results The limited data indicates that β3-adrenoceptor agonists reduce bladder fibrosis and hypertrophy and may induce cell proliferation. On the other hand, limited data also indicate that detrusor relaxation responses can partly desensitize with prolonged agonist exposure, possibly off-setting effects on fibrosis and hypertrophy. Conclusions Further long-term studies with β3-adrenoceptor agonists are needed to clarify the role of such processes in clinical improvement of patients with overactive bladder syndrome occurring at time points later than 4 weeks after initiation of treatment.