Tolterodine, a new antimuscarinic agent: as effective but better tolerated than oxybutynin in patients with an overactive bladder

OBJECTIVE: To compare the efficacy and tolerability of tolterodine with that of oxybutynin in patients with an overactive bladder. PATIENTS AND METHODS: A randomized, double-blind, placebo-controlled, parallel group, multinational phase-III study was conducted in urology and gynaecology clinics in the UK, Republic of Ireland and Sweden. The study enrolled 293 patients with urodynamically confirmed bladder overactivity, increased frequency of micturition (> or = micturitions/24 h) and symptoms of urgency and/or urge incontinence (> or = 1 episode/24 h). Patients received either tolterodine (2 mg twice daily) or oxybutynin (5 mg three times daily) or placebo. Doses could be reduced, to prevent withdrawal, to 1 mg or 2.5 mg, respectively. The main outcome measures were the mean change from baseline in frequency of micturition/24 h, the number of incontinent episodes/24 h and volume voided per micturition. RESULTS: After 12 weeks' treatment, the mean frequency of micturition decreased by 21% and 19.5% in those receiving tolterodine (n = 118) and oxybutynin (n = 118), respectively, and by 10.5% in those on placebo (n = 57). Among those with urge incontinence at baseline (75% of patients), the mean number of incontinent episodes decreased by 47%, 71% and 19%, respectively, in those receiving tolterodine, oxybutynin and placebo. The effect of tolterodine and oxybutynin on these two micturition variables was statistically equivalent. There was also a comparable increase in mean volume voided per micturition in the tolterodine (27%) and oxybutynin groups (31%), compared with 7% in the placebo group. Dry mouth was the most common adverse event and was reported with greater frequency and intensity among patients receiving oxybutynin than among those receiving either tolterodine or placebo. In the oxybutynin group, more patients also withdrew because of adverse events and a greater proportion required dose reduction as a result of adverse events. Despite dose reduction, the frequency of adverse events and the intensity of dry mouth remained higher among those receiving oxybutynin (2.5 mg three times daily) than in patients who remained on tolterodine 2 mg twice daily. CONCLUSION: Tolterodine 2 mg twice daily is effective and well tolerated in the treatment of bladder overactivity. Tolterodine was better tolerated than oxybutynin, particularly with respect to the frequency and intensity of dry mouth, but had comparable clinical efficacy. The superior tolerability of tolterodine therefore allows more patients to remain on effective therapy than the current most commonly prescribed agent for the treatment of the overactive bladder.