Recommended Treatment for a 15-kg Child with Bacterial Meningitis
For a 15-kg child with bacterial meningitis, administer IV ceftriaxone 1500 mg (100 mg/kg) once daily (Option C), as this is the guideline-recommended empiric dosing for pediatric meningitis in children over 28 days of age. 1
Dosing Rationale
The American Academy of Pediatrics (AAP) guidelines explicitly recommend ceftriaxone 100 mg/kg per day for bacterial meningitis in children 29-60 days old, administered either once daily or divided every 12 hours. 1 For this 15-kg child, this equals 1500 mg daily.
The FDA label confirms that for meningitis treatment, the initial therapeutic dose should be 100 mg/kg (not to exceed 4 grams), with a total daily dose of 100 mg/kg/day thereafter, which can be administered once daily or in equally divided doses every 12 hours. 2
Once-daily dosing (1500 mg as a single dose) is superior to twice-daily dosing (750 mg every 12 hours) for achieving adequate CSF penetration. Recent pharmacokinetic modeling demonstrates that 100 mg/kg once daily achieves 88% probability of target attainment at 24 hours versus only 53% for the divided twice-daily regimen. 3
Why Other Options Are Incorrect
Options A and D (penicillin + gentamicin) are inadequate for empiric meningitis coverage because they lack reliable activity against common pediatric meningitis pathogens, particularly Streptococcus pneumoniae and Haemophilus influenzae. 1
Penicillin-gentamicin combinations are reserved for neonates ≤28 days old when Listeria monocytogenes and Group B Streptococcus are primary concerns. 1 This 15-kg child is clearly beyond the neonatal period.
Option B (750 mg every 12 hours) provides the correct total daily dose but uses suboptimal dosing frequency. While this equals 100 mg/kg/day total, dividing it into twice-daily dosing results in lower CSF concentrations and reduced probability of maintaining therapeutic levels throughout the dosing interval. 3
Administration Details
Administer ceftriaxone as an IV infusion over 30 minutes (60 minutes only required in neonates to reduce bilirubin encephalopathy risk). 2
Reconstitute to a concentration between 10-40 mg/mL using compatible IV diluent. 2 For 1500 mg, this typically means diluting in 40-150 mL of normal saline or dextrose solution.
Never use calcium-containing solutions (Ringer's lactate, Hartmann's solution) for reconstitution or concurrent administration due to precipitation risk. 2
Duration and Monitoring
Continue therapy for 7-14 days depending on clinical response and identified pathogen. 2
For Streptococcus pneumoniae, therapy should continue at least 10-14 days. 1
Consider adding vancomycin 60 mg/kg/day divided every 8 hours if the child has recently traveled to areas with penicillin-resistant pneumococcus or if Gram stain suggests resistant organisms. 1
Common Pitfalls to Avoid
Do not use ampicillin-based regimens as monotherapy for empiric meningitis coverage in children beyond the neonatal period—they lack adequate coverage for common pathogens. 1
Do not underdose at 50 mg/kg/day (the dose used for non-CNS infections)—meningitis specifically requires 100 mg/kg/day for adequate CSF penetration. 2, 4
Do not assume twice-daily dosing is equivalent to once-daily dosing simply because the total daily dose is the same—pharmacokinetic data clearly favor once-daily administration for CSF penetration. 3