Nitrofurantoin Dosing for Uncomplicated UTI
For uncomplicated urinary tract infections in women, use nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days. 1
Standard Dosing for Women
The recommended regimen is 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 84-90% and bacterial cure rates of 92% at early follow-up (5-9 days post-treatment). 2
A 7-day course (100 mg twice daily) is an acceptable alternative with clinical cure rates of 89-93%, showing equivalent efficacy to ciprofloxacin and trimethoprim-sulfamethoxazole. 2
Avoid 3-day regimens (100 mg four times daily) due to inferior efficacy, with only 88% clinical cure and 74% bacterial cure rates. 2
Dosing for Men
For males with uncomplicated UTI, use 100 mg orally every 6 hours (four times daily) for 7-14 days, with 14 days recommended when prostatitis cannot be excluded. 3
Be aware that nitrofurantoin has substantially lower efficacy in males, with a 25% failure rate compared to 10-16% in females—this should influence antibiotic selection. 3
Special Population Dosing
For vancomycin-resistant Enterococcus (VRE) UTIs: Use 100 mg orally four times daily. 1, 2
For children ≥12 years: Use the adult dose of 100 mg twice daily. 2
For children <12 years: Use 5-7 mg/kg/day divided into 4 doses (maximum 100 mg/dose) for 7 days. 1, 2
Critical Contraindications
Do not use nitrofurantoin if creatinine clearance is <60 mL/min, as inadequate urinary drug concentrations prevent bactericidal activity and increase toxicity risk, particularly peripheral neuropathy. 3, 2
Avoid nitrofurantoin if early pyelonephritis is suspected, as it does not achieve adequate tissue concentrations for upper tract infections. 1, 2
Important Nuance on Renal Function
While guidelines strictly contraindicate use below CrCl <60 mL/min, one retrospective study found nitrofurantoin was highly effective in patients with CrCl 30-60 mL/min (69% overall eradication rate), with failures primarily occurring only when CrCl <30 mL/min. 4 However, another study demonstrated a significantly increased risk of pulmonary adverse events requiring hospitalization in patients with CrCl <50 mL/min (HR 4.1). 5 Given the increased toxicity risk, adhere to the guideline recommendation and avoid use when CrCl <60 mL/min.
Common Adverse Effects
Nausea and headache are the most common side effects, occurring in 5.6-34% of patients depending on the study. 1, 2
Ensure adequate hydration during treatment to prevent crystal formation. 1