Pharmacokinetics and effects of intravesical oxybutynin on the paediatric neurogenic bladder

Objective To evaluate the pharmacokinetics of both oxpbutynin and its activ e metabolite, N-desethyl oxybutynin (NDO)I when the drug is instilled direc tly into the bladder in children with myelodysplasia and neurogenic bladder disturbance, in whom it may improve continence and decrease the risk of up per urinary tract deterioration. Patients and methods The study comprised 13 children (five girls and eight boys, mean age 9.3 years, range 1-15) with neurogenic bladders who were tre ated using clean intermittent catheterization and intravesical instillation of a sterile, pharmacy-produced solution of oxybutynin. Steady-state minim um plasma levels of oxybutpnin and NDO, together with their effect on urody namic variables and incontinence, were evaluated, The dose (0.04-0.17 mg/kg , mean 0.1 mg/kg) was instilled twice daily. Results The effects of the drug on incontinence and urodynamic variables we re pronounced, improving both in most cases. Minimum plasma levels were < 0 .3-7.2 ng/mL for oxybutynin and 0.8-14 ng/mL for NDO. The ratio of oxybutyn in to NDO was 0.29-0.83 (mean 0.47). Conclusion There was no clear relationship between minimum plasma levels of the drug or NDO and their clinical effects; however, the combination of ox ybutynin and NDO seemed to be more strongly correlated with the clinical ef fects.