Incontinence drug utilization patterns in Québec, Canada.

Abstract

OBJECTIVE: To assess prescription renewal and switch rates in an elderly population receiving oxybutynin or flavoxate for treatment of urinary incontinence in Quebec. METHODS: Sociodemographic, clinical, and drug claim data for patients > or = 65 years of age, with at least one claim for oxybutynin or flavoxate between January 1, 1994 and December 31, 1997, were randomly extracted from a database maintained by the Régie de l'assurance maladie du Québec (RAMQ). Rates of renewal of the first drug claim and the number of patients switching from one incontinence drug to the other were determined. In addition, survival curves defining the time until cessation of initial treatment were constructed. RESULTS: The oxybutynin (n = 5718) and flavoxate (n = 972) treatment groups were similar in terms of gender (62.1% female) and age (mean age 77). For oxybutynin, 56.8% of the claims were written by general practitioners and 36.6% by urologists compared to 40.5% by general practitioners and 51.4% by urologists for flavoxate. Only 39.3% of the oxybutynin patients renewed their first claims, compared to 36.6% of the flavoxate group. Switch rates were higher for flavoxate patients with more than twice as many patients switching from this drug to oxybutynin than vice versa. Survival curves indicated that there was only an 11.4% probability of a patient taking oxybutynin for 6 months compared to 5.7% for flavoxate patients. CONCLUSIONS: Drug claim renewal rates were low for both oxybutynin and flavoxate, suggesting that money spent on these therapies provides an inadequate clinical return on investment since the majority of patients discontinue treatment prematurely.