Efficacy of Intravesical Oxybutynin in Children With Neurogenic Bladder Dysfunction

Malformation of the lumbosacral region (spina bifida) affects the innervation of the bladder in children. The usual evolution leads to a neurological bladder with small capacity, poor compliancy and overactivity, exposing to incontinence and obstruction to the evacuation of urine. It is responsible for renal failure requiring dialysis and transplantation. Current therapeutics aim to evacuate urine and reduce intravesical pressure. It gradually combines 1) intermittent catheterization, 2) anticholinergics, 3) botulinum toxin (Botox®) injection into the detrusor (bladder muscle) by cystoscopy and 4) surgery (vesicostomy, Bricker, enterocystoplasty). Oxybutynin relaxes the detrusor, improves continence and reduces intravesical pressure. It is usually administered per os, but there are contraindications (glaucoma, myasthenia), side effects (constipation, dry mouth). It can be difficult to swallow for children, and drug resistance may develop. It can lead to ineffective treatment requiring therapeutic escalation. The next step, intradetrusor Botox® injection, is invasive (cystoscopy), has a limited duration of action (6 months) and must be performed under general anesthesia in children.

Surgical treatments are effective but irreversible and responsible for morbidity and mortality. A randomized study was performed demonstrating the efficacy of intravesical oxybutynin compared to oral administration in adult patients. This study found a significant increase in bladder capacity and a significant decrease in side effects in the intravesical oxybutynin group. Due to the relative difficulties of intravesical oxybutynin delivery (preparation, cost) and the more invasive nature, it is not used as an alternative to oral oxybutynin.

The hypothesis of this study is that this treatment may have a legitimate place in the treatment of neurogenic bladder in patients with failure of anticholinergic treatment before a therapeutic escalation requiring an invasive procedure (Botox®, enterocystoplasty) especially in children for whom repeated general anesthesia for Botox® injection may interfere with brain development. In this way, the investigators aim to extend the time to therapeutic escalation in the pediatric population.

The main objective of the trial is to compare the efficacy on maximal bladder capacity of intravesical oxybutynin instillation versus placebo in the treatment of children with overactive neurogenic bladder (spina bifida), performing intermittent catheterization, for whom oral anticholinergic treatment is ineffective or poorly tolerated.