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Updated: Oct 2, 2025
A Neonatal Imaging Model of Gram-Negative Bacterial Sepsis
Published on: August 12, 2020
Ampicillin dosing in premature infants for early-onset sepsis: exposure-driven efficacy, safety, and stewardship
Jennifer Le1, Rachel G Greenberg2,3, YoungJun Yoo1
1Skaggs School of Pharmacy and Pharmaceutical Science, University of California, San Diego, La Jolla, CA, USA.
Insights
Two ampicillin doses of 50 mg/kg are optimal for treating early-onset sepsis (EOS) in preterm infants. This regimen achieves bactericidal exposures while minimizing potential neurotoxicity risks.
Area of Science:
- Neonatal pharmacology
- Infectious disease in neonates
- Pharmacokinetics and pharmacodynamics
Background:
- Early-onset sepsis (EOS) is a critical concern in preterm neonates.
- Ampicillin is a standard treatment for EOS, but optimal dosing requires careful consideration of efficacy and safety.
- Preterm infants have unique physiological characteristics that affect drug metabolism and distribution.
Purpose of the Study:
- To determine the optimal ampicillin dosing regimen for empiric early-onset sepsis (EOS) therapy in preterm neonates.
- To evaluate ampicillin concentrations in relation to minimum inhibitory concentration (MIC) and neurotoxicity thresholds.
- To assess the duration of effective drug exposure within a 48-hour window.
Main Methods:
- Simulation of ampicillin concentrations in preterm newborns (birthweight < 1500g; gestational age 22-27 weeks).
- Analysis of three dosing regimens: high (100 mg/kg Q8hr), medium (100 mg/kg Q12hr), and standard (50 mg/kg Q12hr).
- Evaluation of drug concentrations above MIC, below the neurotoxicity threshold (Cmax ≤ 140 mcg/mL), and duration of exposure.
Main Results:
- All regimens achieved concentrations above MIC through 48 hours, but Cmax exceeded the neurotoxicity threshold in some cases.
- The standard 2-dose regimen (50 mg/kg) maintained concentrations above MIC within the 48-hour culture window and below the neurotoxicity level.
- Infants with earlier gestational age (22-24 weeks) exhibited higher ampicillin concentrations and longer exposure durations compared to those 25-27 weeks.
Conclusions:
- Two ampicillin doses of 50 mg/kg provide optimal bactericidal exposures for EOS in preterm infants.
- This dosing strategy effectively balances therapeutic efficacy with minimized potential for neurotoxicity.
- Gestational age is a significant factor influencing ampicillin pharmacokinetics in preterm neonates.
Objective:
Define optimal ampicillin dosing for empiric early-onset sepsis (EOS) therapy in preterm neonates.
Study Design:
We simulated ampicillin concentrations in newborns (birthweight < 1500 g; gestational age 22-27 weeks), summarizing three 48 h regimens: high 100 mg/kg Q8hr, medium 100 mg/kg Q12hr, and standard 50 mg/kg Q12hr. Concentration data were analyzed for concentration above minimum inhibitory concentration (MIC), below neurotoxicity threshold (Cmax ≤ 140 mcg/mL), and duration limited to 48 h.
Results:
Among 34,689 newborns, all dosing regimens provided concentrations above MIC through 48 h, but Cmax exceeded the neurotoxicity threshold. With the 4-dose standard regimen, >90% maintained concentrations >MIC beyond 48 h. With the 2-dose regimen, newborns maintained the mean concentration >MIC within the 48 h culture window and below neurotoxicity level. Infants 22-24 weeks' gestation had higher drug concentrations and more prolonged exposure duration than 25-27 weeks' gestation.
Conclusions:
For EOS in preterm infants, two ampicillin doses (50 mg/kg) provided optimal bactericidal exposures, while minimizing potential toxicity.
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For bacterial pneumonia, antibiotics serve as the cornerstone of therapy. Initial treatment often begins with empirical antibiotics, tailored to the anticipated causative organism and adjusted based on culture results. Key antibiotic choices include: