Nitrofurantoin Dosing for Uncomplicated UTIs
For uncomplicated urinary tract infections (UTIs) in women, the recommended dosage of nitrofurantoin is 100 mg twice daily for 5 days in the form of nitrofurantoin monohydrate/macrocrystals. 1
Recommended Dosing Regimens by Patient Population
Women with Uncomplicated UTIs
- Nitrofurantoin monohydrate/macrocrystals: 100 mg twice daily for 5 days 2, 1
- Alternative formulation: Nitrofurantoin macrocrystals 50-100 mg four times daily for 5 days 1
Men with UTIs
- Nitrofurantoin 100 mg every 6 hours for 7-14 days (14 days recommended when prostatitis cannot be excluded) 3
Efficacy Data
- Clinical cure rates with nitrofurantoin range from 88-93% for uncomplicated UTIs in women 1, 4
- Bacterial cure rates range from 81-92% 1, 4
- The 5-day regimen of nitrofurantoin monohydrate/macrocrystals (100 mg twice daily) has been shown to be equivalent to trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days) in clinical and microbiological cure rates 1
- Early clinical cure rates are approximately 90% 2
Important Contraindications and Precautions
- Contraindicated in patients with creatinine clearance <60 mL/min due to inadequate urinary drug concentrations 4, 3
- Avoid in the last three months of pregnancy 5
- Not recommended if early pyelonephritis is suspected 1, 3
Treatment Duration Considerations
- While the Infectious Diseases Society of America (IDSA) and European Society for Microbiology and Infectious Diseases recommend 5-day regimens 2, 1, some UK guidelines suggest 3-day courses 6
- However, there is limited direct evidence supporting 3-day courses of nitrofurantoin, and the 5-day regimen has more robust evidence 6
Alternative First-Line Options When Nitrofurantoin Cannot Be Used
- Fosfomycin trometamol 3 g single dose (slightly lower efficacy than nitrofurantoin) 1, 7
- Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days (only if local resistance rates <20% or if the infecting strain is confirmed susceptible) 2, 1
Common Side Effects
- Nausea and headache are most commonly reported 1
- Adverse event rates range from 5.6-34% across studies 2, 1
- Headache occurs in approximately 10.8% of patients 8
Clinical Pearls
- Nitrofurantoin has maintained good activity against common uropathogens despite decades of use 5
- It is considered a first-line agent due to minimal resistance and limited propensity for collateral damage 1, 4
- For patients with persistent or recurrent symptoms, obtain urine culture with susceptibility testing 3
- In randomized controlled trials, nitrofurantoin has shown significantly better efficacy than placebo in achieving both bacteriological cure and symptomatic relief 9