PLASMA-LEVELS OF OXYBUTYNINE CHLORIDE IN CHILDREN

Anticholinergic adverse-effects in children treated with conventional doses of oxybutynine led us to measure plasma oxybutynine levels in ch ildren. 18 children, aged 5 to 13 y, who required treatment with oxybu tynine chloride for daytime incontinence were studied. Plasma concentr ations were measured on the fifth day of a course of treatment in whic h the dose was adapted to the child's body weight; the dose was given twice daily at 12-hour intervals. In 10 children aged between 5 and 8 y, the mean dose was 0.1 mg.kg(-1) In 8 children aged between 10 and 1 3 years, the mean dose was 0.15 mg.kg(-1). The highest concentration w as usually found between 1 and 2 h after administration. The subsequen t fall in concentration was rapid and after 6 h oxybutynine was no lon ger measurable in 14 of the children. The concentrations found were no t different from those seen in adults given equivalent doses. The resu lts show that plasma concentrations in children were not very differen t from those observed in adults if the dose were adapted to the body w eight of the children. No special differences in paediatric use were r evealed that might explain the particular adverse-effects. The results of the study argue against the dosage regimen proposed before these a dverse events were detected. They strongly favour a dose adapted to th e body weight of the child, with a 12-hour interval between doses.