Metronidazole (Metrogyl) Syrup Dosing in Pediatric Patients
The standard pediatric dose of metronidazole syrup is 7.5 mg/kg per dose, administered three to four times daily, with a maximum of 500 mg per dose. 1
Standard Dosing by Indication
For Anaerobic Infections
- Dose: 7.5 mg/kg per dose administered 3-4 times daily 1
- Duration: 7-10 days depending on clinical response and specific indication 1
- Maximum: 500 mg per dose 1
For Clostridium difficile Infection (CDI)
- Important caveat: Metronidazole is no longer first-line therapy for CDI 2
- Preferred agents: Vancomycin (125 mg orally 4 times daily) or fidaxomicin (200 mg twice daily) are strongly recommended over metronidazole 2
- If metronidazole must be used (limited access to preferred agents): 7.5 mg/kg per dose 3-4 times daily for 10 days, maximum 500 mg per dose 1
- Adult equivalent dosing (for reference): 500 mg orally 3 times daily for 10 days 2
Critical Safety Warnings
Neurotoxicity Risk
- Avoid repeated or prolonged courses due to risk of cumulative and potentially irreversible neurotoxicity 2, 1
- Neurotoxicity can occur at doses as low as 21 mg/kg/day in some cases 3
- Exercise particular caution when total daily doses exceed 40 mg/kg 3
Treatment Failure Management
- If no clinical response within 5-7 days for CDI, switch to oral vancomycin rather than continuing metronidazole 1
- Do not extend metronidazole therapy beyond 14 days without compelling justification 2
Administration Considerations
Monitoring and Follow-up
- Ensure completion of the full treatment course even if symptoms improve 1
- Monitor for common side effects: nausea (most common), metallic taste, gastrointestinal discomfort, headache, and vomiting 4
- No dosage adjustment needed for renal dysfunction, as metronidazole pharmacokinetics are unaffected by renal failure 2, 5
Special Populations
- Hepatic impairment: Dosage reduction is necessary due to decreased clearance 6, 5
- Pregnancy: Should only be used if clearly needed; crosses placental barrier rapidly 6
- Nursing mothers: Secreted in breast milk at concentrations similar to plasma; consider discontinuing nursing or the drug 6
Practical Dosing Example
For a 20 kg child with an anaerobic infection:
- Calculation: 20 kg × 7.5 mg/kg = 150 mg per dose
- Frequency: 150 mg three to four times daily
- Duration: 7-10 days 1