Dry mouth with conventional and controlled-release oxybutynin in urinary incontinence

Objective: To compare the efficacy and safety of controlled-release oxybutynin with conventional, immediate-release oxybutynin and determine rates of dry mouth. Methods: Patients (n = 226) who were known to be responsive to anticholinergic therapy and who had seven or more urge incontinence episodes per week were randomized to receive controlled-release oxybutynin or immediate-release oxybutynin. After an initial placebo run-in period, dosing in each began at 5 mg per day and increased weekly by 5 mg per day to a maximum of 20 mg per day or when a balance between improvement of incontinence symptoms and tolerability of side effects was achieved. Rates of urge incontinence and dry mouth were compared. Post hoc Kaplan-Meier survival analysis was used to describe elimination of incontinence episodes by dose and to analyze dry mouth risk by dose. Results: Reductions in urge urinary incontinence episodes from baseline to the end of treatment were 18.6 to 2.9 per week (83% mean decrease) and 19.8 to 4.4 per week (76% mean decrease) in the controlled- and immediate-release oxybutynin groups (P = .36), respectively. At equal doses, comparable proportions of patients in both groups reported the absence of urge incontinence (P = .85). The incidence of dry mouth increased with dose in both groups, but there was no difference in dry mouth rates between the groups: 47.7% and 59.1% for the controlled- and immediate-release oxybutynin (P = .09), respectively. However, Kaplan-Meier analysis to examine first report of dry mouth at a given dose revealed that a significantly lower proportion of patients taking controlled-release oxybutynin had moderate to severe dry mouth (P = .007) or any dry mouth (P = .003) compared with those taking immediate-release oxybutynin. Conclusion: At the same daily dose, controlled- and immediate-release oxybutynin demonstrated comparable efficacy in reduction of urge incontinence episodes. The incidence of dry mouth was dose dependent but equal in both groups; first report of moderate to severe dry mouth was significantly lower in the controlled-release group. (C) 2000 by The American College of Obstetricians and Gynecofogists.