Pharmacokinetics of a new macrolide, roxithromycin, in infants and children.

The pharmacokinetics of roxithromycin was investigated after oral administration of 2.5 mg/kg doses given 12 hours apart during 6 days in infants and children. These 18 subjects suffering from a respiratory tract infection were divided into three age groups: group I less than 18 months, group II less than 5 years, group III less than 13 years. At day 6, the elimination plasma half-life had an average value (mean +/- SD) of 19.8 +/- 9.7 h (group I), 21.0 +/- 9.4 h (group II) and 20.8 +/- 6.9 h (group III), respectively. The maximum concentration of roxithromycin (Cmax) was attained between 1 and 2 hours after dosing with mean values of 10.1 +/- 3.0 mg/l (group I), 8.7 +/- 4.9 mg/l (group II), 8.8 +/- 7.0 mg/l (group III). All the calculated pharmacokinetic parameters did not significantly differ from one group to another. The kinetics of roxithromycin in infants and children seemed to be age independent and showed no accumulation after repeated doses. During 12 hours, the plasma concentrations were above MIC of microorganisms generally present in respiratory tract infections. Two daily doses of 2.5 mg/kg of roxithromycin 12 hours apart may be proposed in infants and children.