Nitrofurantoin Dosing for a 54-pound Pediatric Female
For a 54-pound (24.5 kg) pediatric female with normal renal function, administer nitrofurantoin 5-7 mg/kg/day divided into 4 doses (approximately 30-43 mg four times daily), not to exceed 100 mg per dose, for treatment of uncomplicated urinary tract infections. 1
Weight-Based Dosing Calculation
- Standard pediatric dosing: 5-7 mg/kg/day divided into 4 doses 1
- For this 24.5 kg patient:
- Lower range: 5 mg/kg × 24.5 kg = 122.5 mg/day (approximately 30 mg four times daily)
- Upper range: 7 mg/kg × 24.5 kg = 171.5 mg/day (approximately 43 mg four times daily)
- Maximum single dose: 100 mg per dose 1
Treatment Duration
- Uncomplicated cystitis: 7 days minimum 1
- Recommended duration: At least 3 days after obtaining sterile urine 1
- Standard course: 7-10 days for most pediatric urinary tract infections 2
Clinical Context and Indications
- Approved indication: Uncomplicated urinary tract infections only 1
- NOT recommended for: Pyelonephritis or perinephric abscess 1
- Effective against: Extended-spectrum β-lactamase (ESBL)-producing E. coli, with 98% bacteriological response rates in pediatric patients 2
Age-Specific Considerations
- Not approved: For children <12 years by Taiwan FDA, though widely used off-label with established safety data 1
- Renal function requirement: Normal renal function is essential, as nitrofurantoin requires adequate urinary excretion for efficacy 3, 4
Administration Guidelines
- Dosing frequency: Four times daily (every 6 hours) to maintain therapeutic urinary concentrations 1
- Food administration: Should be given with food to enhance absorption and reduce gastrointestinal side effects 3, 4
- Formulation: Macrocrystalline or monohydrate/macrocrystalline formulations preferred for better tolerability 1
Safety Profile
- Common side effects: Nausea and headache (generally mild) 1
- Serious adverse events: Rare in short-term use; no significant side effects observed in pediatric studies 2
- Monitoring: Serum creatinine should be normal before initiating therapy 1
Common Pitfalls to Avoid
- Underdosing: Using adult fixed-dose regimens (100 mg four times daily) in smaller children can lead to excessive dosing; always calculate weight-based dosing 1
- Inappropriate indications: Do not use for upper urinary tract infections (pyelonephritis), as nitrofurantoin does not achieve adequate tissue concentrations outside the urinary tract 1
- Renal impairment: Contraindicated in patients with impaired renal function, as therapeutic urinary concentrations cannot be achieved 1, 3
- Premature discontinuation: Ensure minimum 7-day course even if symptoms resolve earlier to prevent recurrence 1, 2
Alternative Considerations
- If ESBL-producing organisms: Nitrofurantoin remains highly effective (96% non-scarring rate on follow-up imaging) and is preferred over parenteral alternatives for uncomplicated lower UTI 2
- Treatment failure: If no clinical improvement within 48-72 hours, obtain repeat urine culture and consider alternative diagnosis or resistant organism 2