Purpose: We evaluated the efficacy and safety of transdermal and oral oxybutynin in children with neurogenic detrusor overactivity.
Materials and methods: Children with neurogenic detrusor overactivity 6 to 15 years old and previously receiving oxybutynin were assigned randomly at a 3:1 ratio to treatment with transdermal or oral oxybutynin. Initial dosages (transdermal 1.3, 2.9 or 3.9 mg daily; oral 5, 10 or 15 mg daily), based on pre-study dosages, were adjusted after 2 weeks and then maintained for 12 weeks. The primary efficacy end point was change from baseline to last observation in average urine volume collected by clean intermittent catheterization.
Results: A total of 57 patients were randomized to receive transdermal (41) or oral (16) oxybutynin. Safety data were available for 55 patients and efficacy data were available for 52. Mean +/- SD urine volume increased from 95 +/- 64 ml to 125 +/- 74 ml (p <0.001) with transdermal oxybutynin and from 114 +/- 75 ml to 166 +/- 92 ml (p = 0.002) with oral oxybutynin. Transdermal oxybutynin resulted in significant improvement in all measured urodynamic parameters. Similar trends and a significant increase in maximal cystometric bladder capacity were observed in the smaller oral oxybutynin group. There were 12 treatment related adverse events noted with transdermal oxybutynin (mild skin reaction) and 1 with oral oxybutynin (vasodilatation). The ratio of N-desethyloxybutynin-to-oxybutynin plasma concentrations was substantially lower with transdermal (1.4) than with oral (6.7) oxybutynin.
Conclusions: Transdermal oxybutynin was a well tolerated and effective alternative to oral oxybutynin in treating neurogenic detrusor overactivity in children who previously tolerated oxybutynin.