Nitrofurantoin Dosing for Uncomplicated UTI
For uncomplicated urinary tract infections in women, prescribe nitrofurantoin monohydrate/macrocrystals 100 mg orally twice daily for 5 days. 1, 2
Standard Dosing Regimen for Women
The recommended dose is 100 mg orally twice daily for 5 days, as endorsed by both the Infectious Diseases Society of America (IDSA) and the 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%, though the 5-day regimen is preferred to minimize adverse effects while maintaining efficacy. 1, 2
Alternative Dosing Formulations
Nitrofurantoin macrocrystals can be dosed at 50-100 mg four times daily for 5 days, though the twice-daily formulation is more convenient and equally effective. 1
Avoid 3-day regimens (100 mg four times daily), as they demonstrate inferior efficacy with only 88% clinical cure and 74% bacterial cure rates compared to 5-day courses. 2
Special Population Considerations
Males with UTI
For males with uncomplicated UTI, use nitrofurantoin 100 mg orally every 6 hours (four times daily) for 7-14 days. 3
Treat for 14 days when prostatitis cannot be excluded, as males have substantially higher failure rates (25%) compared to females (10-16%). 3
Be aware that nitrofurantoin's clinical efficacy in males is significantly lower than in females, which should influence antibiotic selection. 3
Pediatric Dosing
For children ≥12 years: use the adult dose of 100 mg twice daily for 7 days. 1, 2
For children <12 years: dose at 5-7 mg/kg/day divided into 4 doses (maximum 100 mg/dose) for 7 days. 1, 2
Vancomycin-Resistant Enterococcus (VRE) UTIs
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, including peripheral neuropathy. 2, 3
Avoid nitrofurantoin if early pyelonephritis is suspected, as it does not achieve adequate tissue concentrations for upper tract infections. 1, 2
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
Adverse event rates are comparable to trimethoprim-sulfamethoxazole (31-38%). 2
Ensure adequate hydration during treatment to prevent crystal formation. 1
When to Consider Alternative First-Line Agents
If creatinine clearance is <60 mL/min, switch to trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days) or fosfomycin (3 g single dose). 2
If local E. coli resistance to trimethoprim-sulfamethoxazole is <20% and the patient has no sulfa allergy, trimethoprim-sulfamethoxazole is an equivalent alternative. 1, 2
Fosfomycin 3 g single dose is an alternative first-line option with slightly lower efficacy (90% vs 95% clinical cure for nitrofurantoin). 1, 2
Follow-Up Recommendations
Routine post-treatment urinalysis or urine cultures are not indicated for asymptomatic patients. 1
For women whose symptoms do not resolve by the end of treatment or recur within 2 weeks, perform a urine culture with susceptibility testing and consider retreatment with a 7-day regimen using another agent. 1