NEW YORK (Reuters Health) - Extended-release oxybutynin and tolterodine are similarly effective for reducing urge urinary incontinence (UUI) and total incontinence episodes in women with overactive bladder, according to a report in the June issue of Mayo Clinic Proceedings. However, micturition frequency is significantly lower with oxybutynin.

In a randomized, double-blind study, Dr. Ananias C. Diokno, of William Beaumont Hospital, Royal Oak, Michigan, and colleagues compared the efficacy of extended-release formulations of oxybutynin and tolterodine in 790 women with overactive bladder. Patients received 10 mg/d oxybutynin or 4 mg/d tolterodine for 12 weeks.

The team reports that of 391 patients who received oxybutynin, 339 (87%) completed the study. Of 399 who received tolterodine, 357 (89%) completed the study.

Improvements in UUI episodes were similar between the groups. In the oxybutynin group, the mean weekly episodes of UUI decreased from 37.1 at baseline to 10.8. In the tolterodine group, the mean weekly episodes decreased from 36.7 to 11.2.

"Oxybutynin participants had a greater decrease in the mean weekly micturition frequency compared with tolterodine participants (28.4 versus 25.2, respectively, compared to means of 66.4 and 71.1, respectively; p = 0.003)," Dr. Diokno and colleagues report.

Twenty-three percent of oxybutynin patients and 16.8% of those on tolterodine reported total dryness in their last 7-day 24-hour voiding diary (p = 0.03).

Dry mouth was the most common adverse event, and was reported by 29.7% and 22.3% of patients in the oxybutynin and tolterodine groups, respectively (p = 0.02). Adverse events were generally mild, according to the authors. The rate of discontinuation of treatment due to adverse events was similar between the groups.

Dr. Diokno and colleagues say that the flexible dosing schedule of extended release oxybutynin is an advantage in achieving "the optimal balance between efficacy and tolerability because of the wide range of approved doses."

Mayo Clin Proc 2003; 78:687-695.

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