Meropenem is an antibiotic that is commonly used to treat serious infections. Although it is used in premature and young infants, the correct dose is not known. The purpose of this study is to determine the correct dose and the safety of meropenem for the treatment of complicated intra-abdominal infections in these young babies.

This study will evaluate the safety, tolerability and PK-PD of meropenem in infants <91 days of age with suspected and complicated intra-abdominal infections.

The specific aims of this trial are:

1. To characterize meropenem single-dose and multiple-dose PK in subjects with suspected and complicated intra-abdominal infections.
2. To characterize the safety profile of meropenem in the treatment of suspected and complicated intra-abdominal infections.
3. To assess collected efficacy data for meropenem for the treatment of suspected and complicated intra-abdominal infections.

• Necrotizing Enterocolitis
• Intra-Abdominal Infection

• Drug: meropenem

  Infants <32 weeks:

  < 2 week PNA: 10mg/kg q 12hr 2-4 weeks PNA: 20mg/kg q 12hr >4 weeks PNA: 20mg/kg q 8hr

  Infants ≥32 weeks:

  < 2 weeks PNA: 20mg/kg q 12hr 2-4 weeks PNA: 20mg/kg q 8hr >4 weeks PNA: 30mg/kg q 8hr

  Other Name: Merrem
• Drug: meropenem

  If the Low Dose arm is tolerated:

  MEDIUM DOSE

  Infants <32 weeks:

  < 2 week PNA: 20mg/kg q 12hr 2-4 weeks PNA: 20mg/kg q 8hr >4 weeks PNA: 30mg/kg q 8hr

  Infants ≥32 weeks:

  < 2 weeks PNA: 20mg/kg q 8hr 2-4 weeks PNA: 30mg/kg q 8hr >4 weeks PNA: 40mg/kg q 8hr

  Other Name: Merrem
• Drug: meropenem

  If the Medium dose arm is tolerated:

  HIGH DOSE

  Infants <32 weeks:

  < 2 week PNA: 20mg/kg q 8hr 2-4 weeks PNA: 30mg/kg q 8hr >4 weeks PNA: 40mg/kg q 8hr

  Infants ≥32 weeks:

  < 2 weeks PNA: 30mg/kg q 8hr 2-4 weeks PNA: 40mg/kg q 8hr >4 weeks PNA: 50mg/kg q 8hr

  Other Name: Merrem

• 1: Active Comparator
  Low dose meropenem 10 mg/kg
  Intervention: Drug: meropenem
• 2: Active Comparator
  Medium dose meropenem 20 mg/kg
  Intervention: Drug: meropenem
• 3: Active Comparator
  High dose meropenem 30 mg/kg
  Intervention: Drug: meropenem

Inclusion Criteria:

• Written permission from parent or legal guardian Age younger than 91 days Likely to survive beyond the first 48 hours after enrollment Sufficient intravascular access (either peripheral or central) to complete study procedures Physical, radiological, and/or bacteriological findings of a complicated intra-abdominal infection. These include peritonitis, NEC Grade II or higher by Bell's criteria, Hirschsprung's disease with perforation, spontaneous perforation, meconium ileus with perforation, bowel obstruction with perforation, as evidenced by free peritoneal air on abdominal radiograph, intestinal pneumatosis or portal venous gas on abdominal radiographic examination.

OR 2) Possible NEC OR 3) Otherwise receiving meropenem per local standard of care

Exclusion Criteria:

• Renal dysfunction evidenced by urine output <0.5 mL/hr/kg over the prior 24 hours Serum creatinine >1.7 mg/dL History of clinical seizures or EEG confirmed seizures Concomitant treatment with another carbapenem at the time of informed consent Any condition which would make the subject or the caregiver, in the opinion of the investigator, unsuitable for the study