Comparison of the concentrations of ceftazidime in the serum of newborn infants after intravenous and intramuscular administration

The concentrations of ceftazidime in serum were studied in 16 preterm and term neonates to whom a single dose of 50 mg/kg had been administered intramuscularly or intravenously. After intramuscular injection, concentrations of ceftazidime in serum were comparable to those obtained with the intravenous dose, although they were more variable. Peak serum levels ranging from 50 to 102 micrograms/ml were reached 30 to 60 min after intramuscular injection. The concentrations declined monoexponentially after the peak, with a mean half-life of 3.8 +/- 1.1 h. Concentrations of ceftazidime in serum declined biexponentially after intravenous injection, with a terminal half-life of 4.7 +/- 1.5 h.