Meropenem Dosing for a 2.5-Month-Old Infant Weighing 2.67 kg
For this 2.67 kg, 2.5-month-old infant, administer meropenem 20 mg/kg every 8 hours (approximately 53 mg per dose) as a 30-minute intravenous infusion.
Dose Calculation Algorithm
The precise dose depends on gestational age at birth and current postnatal age 1, 2:
If Term Infant (≥32 weeks gestational age):
- Postnatal age ≥14 days (which applies to a 2.5-month-old): 30 mg/kg every 8 hours 1
- Calculated dose: 30 mg/kg × 2.67 kg = 80 mg per dose every 8 hours 1
If Premature Infant (<32 weeks gestational age):
- Postnatal age ≥14 days: 20 mg/kg every 8 hours 1
- Calculated dose: 20 mg/kg × 2.67 kg = 53 mg per dose every 8 hours 1
Volume Calculation for Administration
Meropenem is typically reconstituted to standard concentrations 2:
If using 50 mg/mL concentration:
- For 80 mg dose (term infant): 1.6 mL per dose
- For 53 mg dose (preterm infant): 1.06 mL per dose
If using 20 mg/mL concentration:
- For 80 mg dose (term infant): 4 mL per dose
- For 53 mg dose (preterm infant): 2.65 mL per dose
Administration Guidelines
- Infusion time: Administer over 30 minutes as an intravenous infusion 2
- Frequency: Every 8 hours 1, 2
- Maximum dose: Not applicable at this weight, as the calculated dose is well below the 2-gram maximum 2
Critical Considerations for This Patient
Severe Anemia and CHD Context:
- The presence of severe anemia and congenital heart disease does not alter the standard meropenem dosing regimen 2
- However, monitor hemoglobin closely, as diagnostic blood draws for therapeutic drug monitoring may worsen anemia in this vulnerable population 3
- Consider blood conservation strategies given the underlying severe anemia 4
Hematologic Monitoring:
- Monitor complete blood counts closely during meropenem therapy, as pancytopenia (including thrombocytopenia, anemia, and neutropenia) has been reported in preterm neonates receiving meropenem 5
- This is particularly important given the pre-existing severe anemia 5
- If pancytopenia develops, counts typically improve within 4-7 days after discontinuation 5
Common Pitfalls to Avoid
- Do not underdose based on the infant's low weight – use the full mg/kg dose as recommended 1, 2
- Do not use the lower 20 mg/kg dose if the infant is term – term infants ≥14 days old require 30 mg/kg every 8 hours 1
- Do not administer as a bolus injection in infants this young – always use 30-minute infusion 2
- Do not assume the anemia or CHD require dose adjustment – these conditions do not alter meropenem pharmacokinetics requiring dose modification 2