Single-dose pharmacokinetics of ceftriaxone in infants and young children.

The pharmacokinetics of ceftriaxone were studied in five infants (7 to 15 months old) and five young children (24 to 70 months old). Both groups received a single 50-mg/kg dose in an intravenous infusion over 5 min. No major pharmacokinetic differences were observed between the two populations. The total (bound plus unbound) plasma concentration-versus-time data could be described in each case by a biexponential equation. Changes in renal clearance indicated time- and dose- dependent pharmacokinetic behavior. The fraction excreted unchanged in the urine (fu) and the biological half-life (t 1/2 (beta)) were, however, dose independent. The average values were 47% for fu (0 to 12 h) and 6.5 for T 1/2 (beta). Weight-corrected total systemic clearance was C1TS = 0.71 ml/min per kg; volume of distribution was VD (beta) = 394 mg/kg. The data support intravenous administration of 50 mg of ceftriaxone per kg of body weight every 12 h in assessing its activity against Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis in postneonatal-stage pediatric patients.