Nitrofurantoin Dosing for Pediatric UTI Treatment
Recommended Dosing
For a 50-pound (approximately 23 kg) child with a urinary tract infection, nitrofurantoin should be dosed at 5-7 mg/kg/day divided into 4 doses, which translates to approximately 115-160 mg total daily dose, or roughly 30-40 mg every 6 hours, with a maximum single dose of 100 mg. 1
Dosing Calculation Details
- Weight-based dosing: The standard pediatric dose is 5-7 mg/kg/day divided into 4 doses 1
- For a 23 kg child: 115-161 mg/day total
- Practical dosing: 30-40 mg every 6 hours (four times daily)
- Maximum single dose: 100 mg per dose 1
Treatment Duration
- Standard duration: 7 days for uncomplicated lower UTI 1
- Treatment should continue for at least 3 days after obtaining sterile urine 1
- Some evidence supports 10-day courses, particularly for more complex cases 2, 3
Critical Limitations and Contraindications
Nitrofurantoin should NOT be used for:
- Upper UTIs (pyelonephritis): Nitrofurantoin has inadequate tissue penetration and should only be used for lower urinary tract infections (cystitis) 1, 4
- Febrile UTIs in infants: Due to insufficient parenchymal concentrations 4
- Infants under 1 month of age: Risk of hemolytic anemia 1, 5
- Infants under 4 months: Best avoided due to hemolytic anemia risk 1
- Perinephric abscess: Oral formulation is inadequate 1
Clinical Considerations
When Nitrofurantoin is Appropriate
- Uncomplicated cystitis in children over 1 month of age is the primary indication 5
- Excellent activity against E. coli with 95-96% susceptibility rates 6
- Low resistance rates (approximately 2.3%) compared to fluoroquinolones (24%) and trimethoprim-sulfamethoxazole (29%) 6
- Effective against ESBL-producing E. coli in lower UTIs with 98% bacteriological response 2
Alternative First-Line Options
If the child has signs of upper UTI (fever, flank pain, systemic symptoms):
- Mild-to-moderate pyelonephritis: Oral cephalosporins or trimethoprim-sulfamethoxazole (if local resistance permits) 4
- Severe pyelonephritis: Parenteral ceftriaxone 50-75 mg/kg/day divided every 12-24 hours or cefotaxime 150 mg/kg/day every 8 hours 4
Common Pitfalls to Avoid
- Do not use nitrofurantoin empirically without confirming lower UTI: Always distinguish between cystitis and pyelonephritis clinically 4
- Avoid in children who appear toxic or cannot retain oral intake: These require parenteral therapy 4
- Check local resistance patterns: While nitrofurantoin generally maintains excellent susceptibility, local antibiograms should guide therapy 1, 5
- Monitor for side effects: Though generally well-tolerated, watch for gastrointestinal symptoms 2