Neonatal Prescribing

Neonatal prescribing applies to infants in the first 28 days of life, when clearance, distribution and absorption change from day to day. Doses depend on gestational age at birth, postnatal age, postmenstrual age and weight, and the margin between effective and toxic dosing is narrow.

Pharmacokinetic features. Extracellular fluid volume is large and falls over the first week. Glomerular filtration and tubular function are low and rise quickly after the first week. Glucuronidation is immature, so morphine and paracetamol clear slowly. Hypoalbuminaemia and jaundice raise the risk of displaced bilirubin with sulphonamides and ceftriaxone.

Excipients. Neonates cannot clear benzyl alcohol, propylene glycol, ethanol or hyperosmolar sorbitol. Prefer preservative-free products and dilute oral preparations.

Representative term neonate regimens. Preterm infants need the adjustments in the premature dosing article.

• Vitamin K (phytomenadione): 1 mg intramuscularly once at birth (0.5 mg if birth weight under 1.5 kg).
• Early-onset sepsis: amoxicillin or ampicillin 50 mg/kg intravenously every 12 hours in the first 7 days and every 8 hours from day 8, plus gentamicin. Duration 7 to 10 days for proven bacteraemia and 14 to 21 days for meningitis.
• Gentamicin (term): 4 to 5 mg/kg intravenously once daily. Dose and interval vary by region and gestation, and pre-dose level targets under 1 mg/L.
• Herpes simplex: aciclovir 20 mg/kg intravenously every 8 hours for 14 days (skin, eye, mouth disease) or 21 days (central nervous system or disseminated disease). Adjust for kidney function and hydrate well.
• Hypoglycaemia (glucose under 2.6 mmol/L with symptoms or persistent): 2 mL/kg of 10% glucose intravenously over 5 minutes, then an infusion of 10% glucose at 4 to 8 mg/kg/min, adjusted to the blood glucose.
• Seizures: phenobarbital 20 mg/kg intravenously loading dose over 20 minutes, then 3 to 5 mg/kg once daily; level target 15 to 40 mg/L.
• Paracetamol: 10 to 15 mg/kg every 4 to 6 hours, maximum 60 mg/kg/day for term infants. Intravenous: 10 mg/kg every 6 hours, maximum 40 mg/kg/day. Avoid regular use without clear indication.
• Opioid analgesia: morphine 25 to 50 mcg/kg intravenously, repeated every 4 to 6 hours, with continuous respiratory monitoring.

Contraindicated or avoided. Chloramphenicol, cotrimoxazole, ceftriaxone in jaundiced neonates, and any product containing benzyl alcohol.

Gestation and age. Extend dosing intervals for aminoglycosides and vancomycin in the first week and in preterm infants, and shorten them as clearance matures.

Kidney impairment. Check creatinine against the maternal value on day 1 (it reflects maternal level), and reduce renally cleared drugs for oliguria (under 1 mL/kg/h).

Therapeutic hypothermia. Clearance of morphine, phenobarbital and gentamicin falls during cooling, so lower doses are used and levels checked.

Breastfeeding and pregnancy. Maternal drugs reaching the neonate by milk (opioids, benzodiazepines, antiepileptics) need review. In East Africa, neonatal sepsis often needs empirical treatment before cultures, and local resistance patterns decide the second-line choice.

Monitoring. Check heart rate, respiratory rate, oxygen saturation and glucose with each new drug. Measure gentamicin, vancomycin and phenobarbital levels. Review the serum creatinine, bilirubin and electrolytes at least every 48 to 72 hours on prolonged therapy.

Referral and escalation. Every neonatal prescription needs a second check. Seek neonatologist input for any unlicensed dose, any infusion of a vasoactive or opioid drug, and any suspected overdose.

Stopping. Set a stop date for antibiotics at the time of prescribing and stop at 48 hours if cultures are negative and the infant is well.