Metronidazole Dosing for Pediatric Patients
The standard recommended dose of metronidazole for most pediatric infections is 30-40 mg/kg/day divided every 8 hours, with a maximum of 500 mg per dose, for a typical duration of 10 days. 1
General Dosing Framework
The Infectious Diseases Society of America provides clear guidance that establishes 30-40 mg/kg/day divided into three doses as the foundational dosing regimen for most pediatric infections requiring metronidazole 1. This translates to approximately 10-13 mg/kg per dose given every 8 hours, with each individual dose capped at 500 mg 1.
Condition-Specific Dosing Adjustments
Intra-Abdominal Infections
- Use the standard 30-40 mg/kg/day divided every 8 hours as part of combination therapy with aminoglycosides, carbapenems, or advanced-generation cephalosporins 1
- Higher doses within the recommended range may be warranted for severe infections 1
Clostridium difficile Infection (CDI)
Non-severe CDI:
- 7.5 mg/kg/dose three or four times daily (maximum 500 mg per dose) for 10 days 1, 2
- This lower dose is appropriate for initial episodes or first recurrence of non-severe disease 2
Severe CDI:
- Oral vancomycin is strongly preferred over metronidazole for severe or fulminant CDI 2
- If metronidazole must be used intravenously for severe disease, dose at 10 mg/kg/dose three times daily (maximum 500 mg per dose) 1, 2
- Critical pitfall: Do not use metronidazole for recurrent CDI due to lower cure rates, higher recurrence risk, and neurotoxicity concerns with repeated exposure 3
Crohn's Disease (Perianal Disease)
- 10-20 mg/kg/day in divided doses as recommended by the European Crohn's and Colitis Organisation 1
Route of Administration Considerations
- Intravenous dosing at 30 mg/kg per dose once daily has been studied in pediatric appendicitis patients and achieved adequate pharmacokinetic targets for Bacteroides fragilis with MIC ≤2 mcg/mL 4
- Oral dosing at 40-50 mg/kg/day has demonstrated efficacy in anaerobic infections 5
- The traditional every 6-8 hour dosing remains standard in guidelines despite pharmacokinetic data suggesting once-daily dosing may be adequate for certain infections 4
Special Population: Malnourished Children
A critical caveat exists for severely malnourished children: the dose should be reduced by approximately 60% to 12 mg/kg/day due to significantly altered biotransformation and risk of drug accumulation 6. This population requires individualized pharmacokinetic consideration to avoid toxicity.
Duration of Therapy
- Standard duration for most infections is 10 days 1, 2
- Anaerobic infections may require 14-52 days depending on severity and location (e.g., intracranial abscess) 5
Key Clinical Pitfalls to Avoid
- Never exceed 500 mg per individual dose regardless of calculated weight-based dosing 1, 2
- Adjust dosing based on infection severity, using higher doses within the 30-40 mg/kg/day range for severe infections 1
- Remember that metronidazole should be part of a broader antimicrobial regimen for complicated intra-abdominal infections, not monotherapy 1
- For giardiasis, the dose is lower at 15 mg/kg/day divided into three doses for 7 days 7