Evaluating the duration of post-discontinuation therapeutic ampicillin exposures in preterm infants.

OBJECTIVE

Determine if preterm infants have prolonged therapeutic post-discontinuation antibiotic exposures (PDAE) following empiric ampicillin.

STUDY

DESIGN

Prospective study of 27 infants ≤7 days and <37 weeks gestational age (GA) receiving ampicillin (200 mg/kg/day); 49 post-discontinuation PK samples were collected. Exposures were predicted using PK simulations and a prior ampicillin PK model. The probability of target attainment 24- and 36-h after the final ampicillin dose for various minimum inhibitory concentrations (MICs) and the duration of therapeutic PDAE was calculated.

RESULT: At 24- and 36-h after ampicillin, the probability of exposures ≥1 μg/mL was 95% and 60%, respectively. PDAE (≥1 μg/mL) lasted a median 33 h (95% confidence interval: 15, 79), and varied with GA, from median 53 h (<28 weeks GA) to 27 h (34-36 weeks GA).

CONCLUSION

Many preterm infants experience therapeutic exposures at least 24 h after the final ampicillin dose. Shorter courses could be considered.