Can higher doses of oxybutynin improve efficacy in neurogenic bladder?

We evaluated the efficacy and tolerability of higher dose oxybutynin chloride in patients with neurogenic bladder and multiple sclerosis, spinal cord injury or Parkinson's disease.

The study design was a prospective, 12-week dose titration trial of controlled release oxybutynin (OXY-XL). A 7-day washout period was used before initiation of the starting dose of 10 mg OXY-XL. Doses of OXY-XL were increased by 5 mg at weekly intervals to a maximum dose of 30 mg per day guided by patient perception of efficacy versus side effect. Voiding diaries were completed at baseline, and weeks 6 and 12. Post-void residuals were recorded. Criteria for study admission included post-void residual less than 200 ml.

Of the 39 patients enrolled in the study 22 had multiple sclerosis, 10 had spinal cord injury and 7 had Parkinson's disease. There were 29 women (74%) and 10 men (26%). Within 1 week a decrease in the number of voids per day was seen in greater than 50% of the subjects. At the end of the study statistically significant decreases in the number of voids in 24 hours, episodes of nocturia and incontinence episodes were observed. Residual urine remained unchanged from 33.9 +/- 7.6 ml at baseline to 51.3 +/- 10.4 ml after 12 weeks at the final dose (p = 0.17). No patient experienced serious adverse events and none dropped out during the course of the 12-week study. At the end of the study 20.5% of subjects remained on 30 mg, 15.4% on 25 mg, 23.1% on 20 mg, 15.4% on 15 mg and 25.6% on 10 mg OXY-XL.

Aggressive dosing of OXY-XL is safe and effective in patients with neurogenic bladder. Compared with nonneurogenic overactive bladder, higher doses of OXY-XL (15 mg daily or greater) were requested by 74.4% of the patients in our study. The onset of clinical efficacy can occur within 1 week, and doses up to 30 mg are well tolerated and effective in this population.