Clinical pharmacology of ticarcillin in the newborn infant: relation to age, gestational age, and weight.

Ticarcillin, a new penicillin derivative with greater in vitro activity against Pseudomonas than carbenicillin, was given as a single dose of 50 mg/kg intramuscularly on 61 occasions to 54 neonates and young infants. The serum concentrations and rate of elimination varied considerably depending upon gestational age, chronological age, and body weight. Peak serum concentrations depended principally upon the volume of distribution which approximated the extracellular fluid volume of the neonate. The plasma clearance and serum half-life of the drug were determined. From these pharmacokinetic data appropriate groupings according to age and body weight were made and dosages and intervals of administration predicted for clinical trials of efficacy with repeated doses.