Pharmacokinetic model for serum concentrations of ampicillin in the newborn infant.

The time course of ampicillin concentrations in the sera of three newborn infants during and upon termination of intravenous infusion at a constant rate can be described by a two-compartment pharmacokinetic model. The parameters of the model were determined by simultaneously fitting the serum concentration data obtained during and after the infusion by means of a nonlinear regression program with the aid of a digital computer. The half-life of ampicillin in the infants ranged from 2.1 to 2.9 hr; these values are more than twice those observed in adults with normal renal function.