Nitrofurantoin Dosing for Uncomplicated UTI

For uncomplicated urinary tract infections in women, prescribe nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days. 1

Standard Dosing Regimen

The Infectious Diseases Society of America (IDSA) and European Association of Urology consistently recommend 100 mg twice daily for 5 days as the optimal first-line regimen for uncomplicated UTIs in women. 1, 2
This 5-day regimen achieves clinical cure rates of 88-93% and bacterial cure rates of 81-92%. 1, 2
The 5-day course demonstrates equivalent efficacy to trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days) and ciprofloxacin when comparing appropriate duration regimens. 1, 2

Nitrofurantoin macrocrystals can be dosed at 50-100 mg four times daily for 5 days if the monohydrate/macrocrystal formulation is unavailable. 1
Nitrofurantoin macrocrystals prolonged release: 100 mg twice daily for 5 days. 1

Prescribe 100 mg twice daily for 7 days (extended from the 5-day women's regimen) based on limited observational data. 2

Children ≥12 years: 100 mg twice daily for 7 days. 1
Children <12 years: 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

Never prescribe nitrofurantoin when creatinine clearance is <60 mL/min—this is the most common and dangerous prescribing error. 2
Inadequate urinary drug concentrations occur with reduced renal function, leading to treatment failure and increased toxicity risk including peripheral neuropathy. 2
Avoid nitrofurantoin if early pyelonephritis is suspected, as it does not achieve adequate tissue concentrations for upper tract infections. 1
Do not use for complicated UTIs, perinephric abscess, or any suspected upper urinary tract infection. 1, 2

If creatinine clearance <60 mL/min or other contraindications exist:

Fosfomycin trometamol 3 g single dose (preferred alternative). 2
Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days (only if local E. coli resistance <20%). 2

Nausea and headache are most frequently reported, occurring in 5.6-34% of patients. 1, 2
These adverse effects are generally mild and self-limited. 1

Do not order routine post-treatment urinalysis or urine cultures for asymptomatic patients—this is unnecessary and not indicated. 1, 2
For women whose symptoms do not resolve by end of treatment or recur within 2 weeks, perform urine culture with susceptibility testing. 1, 2
If retreatment is needed, assume the organism is not susceptible to nitrofurantoin and use a different antibiotic for 7 days. 2

While some UK guidelines suggest 3-day courses, the strongest evidence from IDSA and European guidelines supports 5 days as the optimal duration balancing efficacy and minimizing resistance. 1, 2
The 3-day regimen lacks direct supporting evidence, and clinical response varies widely among patients. 3
Do not extend treatment beyond 7 days unless symptoms persist, as shorter courses minimize adverse effects while maintaining efficacy. 1

Nitrofurantoin maintains excellent susceptibility rates (95.6% of E. coli isolates) with only 2.3% resistance, compared to 24% resistance to fluoroquinolones and 29% resistance to trimethoprim-sulfamethoxazole. 4
It causes minimal collateral damage to normal flora and has limited propensity for resistance development. 1
Fluoroquinolones should be reserved for more invasive infections despite their high efficacy. 5