Long-term prospective randomized study comparing two different regimens of oxybutynin as a treatment for detrusor overactivity

Objective: Prospective randomized trial to compare two low starting doses of oxybutynin, using an incremental regimen to assess patient compliance and treatment efficacy in the long-term. Study design: Women with detrusor overactivity were included. Oxybutynin was randomly prescribed with a starting dose of either 2.5 mg bd or 5 mg nocte. Instructions were given to increase oxybutynin up to 5 mg tds over a period of 6 weeks fortnightly. After two years we re-contacted all the women, using a specific questionnaire to assess the efficacy, acceptability and compliance with these two different regimens. Twenty-two women in each group were calculated to show a 5% difference with a significance of 0.05 and a power of 0.9. The χ²-test was used to compare the two groups and a P-value <0.05 was considered significant. Results: Ninety-six women were included; 66 (68.75%) (mean age 57.5 years) responded to our questionnaire. Twenty-seven had a starting dose of 2.5 mg oxybutynin twice a day and 39 of 5 mg nocte. 34.8% complained of side effects. Only 19 (43.2%) out of the 44, not on medication anymore abandoned oxybutynin for adverse reactions. Most of the patients stopped oxybutynin within 4 months. 53.0% reported improvement or cure. 39.4% denied any benefit and 7.6% (none still on oxybutynin) did not answer. The two groups did not differ for duration of treatment, improvement with oxybutynin, maximum dose they reached, the present dose, and the present urinary symptoms. Conclusion: This study did not show any advantage in efficacy or compliance with oxybutynin when two different regimens of low starting were used. Two-thirds of patients discontinued the therapy within 4-6 months. Therefore, patients on anticholinergics should be reassessed after 6 months in clinical practice.