Nitrofurantoin Dosing for Uncomplicated UTI

For uncomplicated urinary tract infections in adults, nitrofurantoin macrocrystals should be dosed at 100 mg orally twice daily for 5 days. 1, 2

Standard Adult Dosing

The IDSA and ESMID recommend 100 mg orally twice daily for 5 days as the preferred regimen for uncomplicated UTI in women, achieving clinical cure rates of 84-90% and bacterial cure rates of 92% at early follow-up (5-9 days post-treatment). 1
At 30-day follow-up, clinical cure rates remain robust at 84%, demonstrating sustained efficacy. 1
A 7-day course (100 mg twice daily) is an acceptable alternative with clinical cure rates of 89-93% and bacterial cure rates of 86%, though the 5-day regimen is preferred. 1, 2
Avoid 3-day regimens (100 mg four times daily) due to inferior efficacy, with only 88% clinical cure and 74% bacterial cure rates. 1

Nitrofurantoin macrocrystals can alternatively be dosed at 50-100 mg four times daily for 5 days, though twice-daily dosing is preferred for adherence. 2

For children ≥12 years: Use adult dosing 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 or at least 3 days after obtaining sterile urine. 1, 2

Do not use nitrofurantoin if creatinine clearance is <60 mL/min, as inadequate urinary drug concentrations prevent bactericidal activity and increase toxicity risk. 1 However, one study suggests efficacy may be maintained with CrCl 30-60 mL/min when used appropriately against susceptible organisms, though this contradicts guideline recommendations. 3
Nitrofurantoin is contraindicated if early pyelonephritis is suspected, as it does not achieve adequate tissue concentrations for upper tract infections. 1, 2
Contraindicated in the last three months of pregnancy. 4
Not recommended for perinephric abscess. 2

Nausea and headache are the most common adverse effects, occurring in 5.6-34% of patients depending on the study. 1, 2
Serious side effects such as pulmonary reactions and polyneuropathy mainly occur with long-term use, not with short-term therapy for acute UTI. 4
Adverse event rates are comparable to trimethoprim-sulfamethoxazole (31-38% adverse events). 1

If local E. coli resistance to trimethoprim-sulfamethoxazole is <20% and the patient has no sulfa allergy, trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days is an equivalent alternative. 1, 2
If CrCl <60 mL/min, switch to trimethoprim-sulfamethoxazole or fosfomycin instead. 1
Fosfomycin 3 g single dose is an alternative first-line option with slightly lower efficacy (90% vs 95% clinical cure for nitrofurantoin). 1, 2
For patients with multiple antibiotic allergies including nitrofurantoin allergy, fosfomycin is the optimal choice. 5

The 5-day nitrofurantoin regimen (100 mg twice daily) has been shown equivalent to trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days) in clinical and microbiological cure rates. 2, 6
Nitrofurantoin has similar clinical cure rates to ciprofloxacin and trimethoprim-sulfamethoxazole when comparing 7-day regimens. 1, 2
Despite over 60 years of use, nitrofurantoin retains good activity against E. coli, Staphylococcus saprophyticus, and Enterococcus species with minimal resistance development. 4