Purpose: To compare persistence of oxybutynin or tolterodine therapy among older patients newly prescribed one of these drugs.

Methods: We conducted a retrospective cohort study of residents of Ontario, Canada, aged 66 years and older who were newly prescribed either drug between 1 Jan 2000 and 31 Dec 2007.  Persistence with treatment was defined on the basis of refills for the drug within a grace period equal to 50% of the prescription duration.

Results: We identified 31,996 patients newly treated with oxybutynin and 24,855 newly treated with tolterodine.  After 2 years of follow-up, persistence on oxybutynin (9.4%) was significantly lower than that on tolterodine (13.6%, p less than 0.0001).  The median time to discontinuation of oxybutynin and tolterodine was 68 and 128 days, respectively.

Conclusions: The authors conclude that their findings suggest that the tolerability of these drugs differs substantially.