Nitrofurantoin Dosing for Uncomplicated UTI
For uncomplicated urinary tract infections in women, prescribe nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days. 1, 2
Standard Dosing Regimen
The recommended dose is nitrofurantoin monohydrate/macrocrystals 100 mg orally twice daily for 5 days, as endorsed by the Infectious Diseases Society of America (IDSA) and European Society for Microbiology and Infectious Diseases (ESMID). 1, 2
This 5-day regimen achieves clinical cure rates of 84-93% and bacterial cure rates of 81-92%, with sustained efficacy at 30-day follow-up (84% clinical cure). 1, 2
The 5-day duration represents the optimal balance between efficacy and minimizing antibiotic exposure, making it superior to shorter 3-day regimens which show lower bacterial cure rates (74%). 2
Alternative Duration Option
A 7-day course (100 mg twice daily) is acceptable if you prefer a longer duration, with clinical cure rates of 89-93% and bacterial cure rates of 86%. 2
The 7-day regimen shows equivalent efficacy to ciprofloxacin and trimethoprim-sulfamethoxazole when comparing similar duration courses. 1, 2
Special Dosing Situations
For vancomycin-resistant Enterococcus (VRE) UTIs specifically, increase the frequency to 100 mg four times daily (every 6 hours) for 7-10 days until clinical resolution. 1, 3
For children ≥12 years, use the adult dose of 100 mg twice daily for 5 days. 1
For children <12 years, dose at 5-7 mg/kg/day divided into 4 doses (maximum 100 mg/dose) for 7 days. 1
Critical Contraindications to Avoid
Do not prescribe nitrofurantoin if creatinine clearance is <60 mL/min (some sources say <30 mL/min for elderly patients), as inadequate urinary drug concentrations prevent bactericidal activity and increase toxicity risk, particularly peripheral neuropathy. 1, 2
Avoid nitrofurantoin if early pyelonephritis is suspected, as it does not achieve adequate renal tissue concentrations for upper tract infections—use fluoroquinolones or trimethoprim-sulfamethoxazole instead. 1, 2
Do not use for complicated UTIs (structural/functional abnormalities, obstruction, instrumentation, pregnancy) or in men with suspected prostatitis, as nitrofurantoin does not penetrate prostatic tissue adequately. 1
When to Choose Alternative First-Line Agents
If local E. coli resistance to trimethoprim-sulfamethoxazole is <20%, consider trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days as an equivalent alternative with similar 90% clinical cure rates. 1, 2
Fosfomycin trometamol 3 g single dose is another first-line alternative with slightly lower efficacy (90% vs 95% clinical cure for nitrofurantoin). 1, 2
Reserve fluoroquinolones (ciprofloxacin, levofloxacin) for more invasive infections due to resistance concerns and collateral damage, despite their 95% clinical cure rate. 1, 4
Expected Adverse Effects
Nausea and headache are the most common side effects, occurring in 5.6-34% of patients depending on the study. 1, 2
Serious pulmonary and hepatic toxicity are extremely rare, occurring in 0.001% and 0.0003% of cases respectively. 1
Advise patients to ensure adequate hydration during treatment to prevent crystal formation. 1