Age-associated changes in ceftriaxone pharmacokinetics.

Ceftriaxone pharmacokinetic parameters were compiled from recent publications. The subjects (27 female, 93 male) were from 1 day to 92 years old and appeared to have normal renal and hepatic function. In 1- to 8-day-old neonates, the half-life averaged 19 hours; it declined to 6.3 hours in 1- to 6-year-old subjects and then increased gradually throughout the remainder of the life-span to 14 hours in 75- to 92-year-old subjects. The age-associated changes in half-life appeared to result from changes in systemic clearance. The fraction of the dose eliminated renally averaged 70% in neonates and declined throughout childhood to 40 to 60% in adults, in whom it was age invariant. No clinically significant differences between males and females were detected in ceftriaxone kinetic parameter values. Plasma protein binding of ceftriaxone (100 mg/L) was about 70% in neonates and it increased throughout childhood to the adult value of 90 to 95%. To achieve a given free concentration of ceftriaxone, the same dosage per unit surface area can be used for children and adults, provided glomerular filtration and biliary secretion function are normal for age. Dosage should be reduced by as much as a factor of 5 in neonates less than 1 week of age and perhaps by a factor of 2 in the very old.