Nitrofurantoin Dosing for Adult UTI
For uncomplicated UTI in adult women, use nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days. 1
Standard Dosing for Women
The Infectious Diseases Society of America (IDSA) and European Society for Microbiology and Infectious Diseases (ESMID) recommend nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days as first-line therapy for uncomplicated UTI in women. 1
This 5-day regimen achieves clinical cure rates of 88-93% and bacterial cure rates of 81-92%. 1
The 5-day course is superior to single-dose fosfomycin, with 70% clinical resolution versus 58% for fosfomycin at 28 days (12% absolute difference, P=0.004). 2
Dosing for Men
For men with uncomplicated UTI, use nitrofurantoin 100 mg every 6 hours (four times daily) for 7-14 days. 3
Use the 14-day duration when prostatitis cannot be excluded, as nitrofurantoin does not penetrate prostatic tissue adequately. 3
Be aware that nitrofurantoin has substantially lower efficacy in males (25% failure rate) compared to females (10-16% failure rate), which should influence antibiotic selection. 3
Special Pathogen Considerations
For vancomycin-resistant enterococci (VRE) UTI, use nitrofurantoin 100 mg four times daily. 1, 4
Continue treatment for 7-10 days until clinical resolution for enterococcal UTIs, rather than the standard 5-day course. 4
Critical Contraindications and Precautions
Do not use nitrofurantoin if creatinine clearance is below 60 mL/min due to inadequate urinary drug concentrations and increased risk of peripheral neuropathy and toxicity. 1, 3, 4
Avoid nitrofurantoin if early pyelonephritis is suspected, as it does not achieve adequate renal tissue concentrations. 1
Do not use for complicated UTIs (structural/functional abnormalities, obstruction, instrumentation) or suspected prostatitis in men. 1
Alternative Formulation
- Nitrofurantoin macrocrystals can be dosed at 50-100 mg four times daily for 5 days as an alternative formulation. 1
Common Pitfalls to Avoid
Ensure adequate hydration during treatment to prevent crystal formation. 1
Do not extend treatment beyond 7 days in women unless symptoms persist, as shorter courses minimize adverse effects while maintaining efficacy. 1
Most common side effects are nausea and headache, with adverse event rates of 5.6-34%. 1
Routine post-treatment cultures are not indicated for asymptomatic patients. 1
For persistent or recurrent symptoms within 2 weeks, obtain urine culture with susceptibility testing and consider retreatment with a 7-day regimen using another agent. 1