Ampicillin and hetacillin pharmacokinetics in normal and anephric subjects

Plasma concentrations o f ampicillin and hetacillin were measured after intravenous administration to anephric patients (on and o$ hemodialysis) and to normal subjects. Hetacillin, an inactive precursor of ampicillin, can be considered chemotherapeutically equivalent to ampicillin because of its rapid, complete hydrolysis to ampicillin in plasma. In normal subjects, 92 ± 8 per cent o f a dose of ampicillin is excreted by the kidney; in patients with impaired renal function there is a marked retention of the antibiotic. Equations were developed to quantitate drug dialysis from plasma, and it was found that 40 per cent o f an ampicillin dose was usually dialyzed in 7.5 hours. The data from this study, along with ampicillin clearances from patients with partial renal function, were used to determine the maintenance dose requirements of ampicillin for patients with various degrees of renal impairment.