The goal of this clinical trial is to learn if preterm infants who are prescribed antibiotics shortly after birth can safety receive a shorter course of antibiotics (24 to 36 hours instead of 48 hours). The main questions it aims to answer are:

• Does short-course ampicillin provide high enough levels of ampicillin at 48 hours?
• Is short-course ampicillin safe for preterm infants to receive?

Preterm infants who are being prescribed ampicillin by their doctor and enroll in the study will stop ampicillin after a shorter than typical course, and researchers will collect blood samples to measure their ampicillin levels and follow them clinically to see how they do after receiving short-course ampicillin.

Participants will:

• stop ampicillin earlier than 48 hours (between 24 to 36 hours, depending on how premature they are and the dosing of ampicillin their doctor has prescribed)
• have a blood sample collected around 48 hours from when they started ampicillin
• have their data collected until 30 days after they receive short-course ampicillin, or until hospital discharge, whichever is sooner

OPTI-Amp is a prospective, open-label, non-randomized pharmacokinetic and safety trial of short-course ampicillin administered to preterm neonates in the Neonatal Intensive Care Unit (NICU) at Duke.

The objectives of the study are to 1) evaluate whether short-course ampicillin provides therapeutic exposures for 48 hours from ampicillin initiation for preterm neonates undergoing evaluation of early onset sepsis (EOS) and 2) evaluate the safety of short-course ampicillin compared to standard empiric ampicillin. The prescribing of drugs to infants will not be part of this protocol.

Approximately 60 neonates ≤34 weeks gestational age and <7 days postnatal age at the time of screening, who are receiving empiric ampicillin prescribed per standard of care (SOC) by their treating provider will be enrolled in the study. Participants will be in the study up to 30 days or hospital discharge, whichever is sooner. Enrolled infants who receive short-course ampicillin will have a pharmacokinetic sample collected at 48 (+/-2) hours from the time that ampicillin was initiated. Additional opportunistic pharmacokinetic (PK) samples can be collected between the final ampicillin dose (time of enrollment) and 72 hours from ampicillin initiation if the patient is receiving other SOC labs; however, these are not required. Demographic information, clinical data, and biospecimen information (including date and time of sample collection) will also be collected for enrolled participants.

All enrolled infants will be in the safety population. Those with at least one PK sample will be included in the PK population. In addition to the risks of blood drawing and loss of confidentiality, there may be a risk of under treatment of EOS if clinical cultures result positive after ampicillin discontinuation and therapeutic exposure is not maintained between 24 or 36 hours until 48 hours. Participants that fall under the latter situation will either not be enrolled in the study or will be withdrawn as determined by the study PI.

Inclusion Criteria:

• Documented informed consent from parent/guardian
• Infants admitted to the Duke Neonatal Intensive Care Unit (NICU)
• less than or equal to 34 completed weeks gestational age (GA) at birth and < 7 days of life at time of screening
• Prescribed ampicillin by provider per standard of care for evaluation of early onset sepsis

Exclusion Criteria:

• Infant on extracorporeal support (e.g., ECMO)
• Positive blood culture or other confirmed infection
• At time of consent, infants with GA <28 completed weeks who have received more than 24 hours of empiric ampicillin OR infants with GA 28 to 34 completed weeks who have received > 32 to 36 hours of ampicillin, depending on dosing regimen
• Has major congenital abnormalities where survival to 30 days of life is not expected
• Failure to obtain consent from parent/guardian
• Receives a course of ampicillin that is longer (i.e., more doses) than the short-course defined regimen for their GA
• Any condition which would make the participant, in the opinion of the investigator, unsuitable for the study

All IPD collected for study purposes will be shared to the NICHD DASH data repository.

The IPD and supporting information will be available once data analysis is complete and will be available per NICHD DASH repository timelines.

Qualified researchers and scientists from academic, non-profit, and for-profit institutions can access data sent to NICHD DASH repository for secondary analysis. Access is controlled, requiring approval from the DASH Data Access Committee (DAC) after the investigator submits a research proposal, a data use agreement (DUA), and a study-specific Data Management and Sharing Plan.