Metronidazole Dosing in Pediatric Patients
For pediatric patients, metronidazole (Flagyl) should be dosed at 7.5 mg/kg/dose three or four times daily (maximum 500 mg per dose) for non-severe infections, and 10 mg/kg/dose three times daily (maximum 500 mg per dose) for severe infections. 1
Dosing Guidelines by Clinical Scenario
Non-Severe Infections
- For initial episodes or first recurrence of non-severe Clostridium difficile infection (CDI): 7.5 mg/kg/dose three or four times daily for 10 days (maximum 500 mg per dose) 1
- Alternative for non-severe CDI: oral vancomycin 10 mg/kg/dose four times daily for 10 days (maximum 125 mg per dose) 1
Severe/Fulminant Infections
- For severe or fulminant CDI: oral vancomycin is recommended over metronidazole (strong recommendation, moderate quality of evidence) 1
- If metronidazole is used in severe infections (typically as adjunctive therapy with vancomycin): 10 mg/kg/dose three times daily intravenously (maximum 500 mg per dose) 1
Recurrent Infections
- For first recurrence of non-severe CDI: same dosing as initial episode (7.5 mg/kg/dose three or four times daily) 1
- For second or subsequent recurrences: oral vancomycin is recommended over metronidazole (weak recommendation, low quality of evidence) 1
Special Considerations
Alternative Dosing Regimens
- Recent pharmacokinetic studies suggest once-daily dosing (30 mg/kg/day) may be effective for certain indications like appendicitis, as it achieves adequate area under the curve (AUC)/minimum inhibitory concentration (MIC) ratios for Bacteroides fragilis with MICs ≤2 mcg/mL 2
- This once-daily dosing regimen showed 96-100% target attainment for organisms with MICs of 2 mcg/mL, comparable to adult dosing of 1000-1500 mg daily 2
Malnourished Children
- Dosage adjustment is necessary in severely malnourished children due to altered drug metabolism 3
- For malnourished pediatric patients, consider reducing the daily dose to approximately 12 mg/kg/day (60% reduction from standard dosing) 3
Route of Administration
- Metronidazole can be administered orally or intravenously depending on the clinical situation 4
- For severe infections requiring parenteral therapy, intravenous dosing of 30 mg/kg/day divided into three doses is recommended 4
- Oral therapy (40-50 mg/kg/day divided) can be used after initial parenteral therapy when clinically appropriate 4
Duration of Therapy
- Standard duration for most infections is 10 days 1
- Longer courses (14-52 days, average 26 days) may be needed for complex infections like intracranial abscesses 4
Clinical Pearls
- Monitor for therapeutic response; peak concentrations typically reach 15-30 mcg/mL and trough levels 4-12 mcg/mL with standard dosing 4
- Metronidazole suspension (250 mg/5 mL) is stable at various storage temperatures (4°C, 25°C, 40°C) for up to 180 days, making it suitable for use in various clinical settings 5
- For certain parasitic infections like giardiasis, alternative nitroimidazoles may be more effective than metronidazole in children 6