Metronidazole Dosing for a 4-Month-Old, 3.8 kg Baby
For a 4-month-old baby weighing 3.8 kg, the appropriate dose of metronidazole syrup (200 mg/5 ml) is 20-30 mg/kg/day divided into 3 doses, which equals 25-38 mg per dose given three times daily.
Dosage Calculation
The most recent evidence indicates that metronidazole dosing for infants should be calculated based on weight:
- Recommended pediatric dose: 20-30 mg/kg/day divided into 3 doses 1
- For a 3.8 kg baby:
- Daily dose: 3.8 kg × (20-30 mg/kg) = 76-114 mg/day
- Per dose (three times daily): 25-38 mg per dose
Administration
Since the syrup concentration is 200 mg/5 ml:
- For a 25 mg dose: 25 mg ÷ (200 mg/5 ml) = 0.625 ml
- For a 38 mg dose: 38 mg ÷ (200 mg/5 ml) = 0.95 ml
Therefore, the appropriate dose range is 0.6-1.0 ml of syrup three times daily.
Clinical Considerations
- Metronidazole is effective against various protozoans (Entamoeba histolytica, Giardia lamblia, Trichomonas vaginalis) and most anaerobic bacteria 2
- Common indications in infants include treatment of:
- Anaerobic infections
- Amoebiasis
- Giardiasis
- Antibiotic-associated colitis (C. difficile)
Important Precautions
- Monitor for potential side effects, which are usually mild to moderate (nausea, abdominal pain, diarrhea)
- Serious but rare side effects include neurotoxicity 3
- Administer with food to improve gastrointestinal tolerability
- Complete the full course of treatment as prescribed to ensure eradication of infection
- Adjust dosing if renal or hepatic impairment is present
Follow-up Recommendations
- Assess clinical response within 48-72 hours of initiating therapy
- If no improvement is observed, reevaluate diagnosis and consider alternative antimicrobial therapy
- Monitor for adverse effects throughout the treatment course