Dry mouth with conventional and controlled-release oxybutynin in urinary incontinence. The Ditropan XL Study Group

To compare the efficacy and safety of controlled-release oxybutynin with conventional, immediate-release oxybutynin and determine rates of dry mouth.

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.

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.

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.