This is a phase I open label multi-dose study to investigative the pharmacokinetics and safety of cefazolin in infants <121 days of age and < 28 weeks gestation with suspected sepsis. There will be two cohorts of 6 infants each: 1) >48 hours of age and ≤28 days and 2) >28 days of age and <121 days of age. The study requires administration of the study drug over 2 days followed by 1 week of safety monitoring. Six 200 µL pK samples will be obtained over the 2 days of drug administration. The risks are reasonable vs. the benefits and have been minimized appropriately. There may be benefit to the subjects (administration of empirical antimicrobial therapy), and information from the study may benefit a large number of other infants in whom the drug is currently being administered despite the lack of PK data in this population.

Inclusion Criteria:

• < 28 weeks gestation at birth

• > 48 hours and <121 days of age at the time of study drug administration

• One of the following:

  • Suspected systemic infection
  • Receiving cefazolin for prophylaxis
  • Receiving cefazolin treatment of a systemic infection

Exclusion Criteria:

• History of anaphylaxis attributed to a β-lactam
• Exposure to cefazolin in the month prior to study
• Serum creatinine > 1.7 mg/dL