Antimuscarinic use and discontinuation in an older adult population

Introduction: Although antimuscarinics are typically the first-line pharmacological treatment option for overactive bladder, patients often discontinue therapy. The aim of this research project is to identify the rate of antimuscarinic discontinuation, switching, and continuation and differences in discontinuation among different antimuscarinics. Methods: Using the 5% random sample of Medicare Claims Data, we identified a cohort of patients aged ≥ 66 years old who newly initiated antimuscarinics between January 1, 2007 and December 31, 2012. Treatment discontinuation was defined as no subsequent fills of the initial antimuscarinic in the days’ supply plus a 30 day grace period. We ascertained percentages of patients who discontinued antimuscarinics, switched antimuscarinics, or died within 12 months of antimuscarinic initiation. Cox proportional hazards models were used to determine time to discontinuation of individual antimuscarinics relative to oxybutynin immediate-release (IR). Results: Among the 42,886 new-users of antimuscarinics, 71.8% discontinued, 10.8% switched, and 3.2% died prior to antimuscarinic discontinuation or switching while only 14.2% continually filled an antimuscarinic for one year. In the multivariable analysis, patients who were initiated on oxybutynin extended-released (ER), tolterodine, trospium, darifenacin, solifenacin, and fesoterodine were significantly less likely to be discontinued therapy compared to oxybutynin IR (p < 0.001). Conclusion: After one year of antimuscarinic initiation, only 14% of older adult patients continuously utilized their initial antimuscarinic therapy suggesting a need for clinical interventions to improve continual use of antimuscarinics.