Macrobid (Nitrofurantoin) Dosing for Uncomplicated UTI
For uncomplicated urinary tract infections in women, the standard dose of Macrobid (nitrofurantoin monohydrate/macrocrystals) is 100 mg twice daily for 5-7 days. 1
Standard Dosing Regimen
The Infectious Diseases Society of America (IDSA) and European Society for Microbiology and Infectious Diseases (ESMID) recommend 100 mg twice daily for 5 days as the optimal first-line regimen for uncomplicated UTIs in women. 1
The European Association of Urology similarly endorses 100 mg twice daily for 5 days as first-line therapy for uncomplicated cystitis. 1
This 5-day regimen achieves clinical cure rates of 88-93% and bacterial cure rates of 81-92%. 1
Efficacy Compared to Alternatives
The 5-day nitrofurantoin regimen (100 mg twice daily) demonstrates equivalent efficacy to trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days) in both clinical and microbiological cure rates. 1
In a head-to-head trial, 5-day nitrofurantoin achieved 84% clinical resolution at 28 days compared to 58% with single-dose fosfomycin, representing a statistically significant 12% absolute difference (P = 0.004). 2
When compared to 7-day regimens of ciprofloxacin and trimethoprim-sulfamethoxazole, nitrofurantoin shows similar clinical cure rates. 1
Alternative Dosing Schedules
For vancomycin-resistant Enterococci (VRE) UTIs specifically, increase the dose to 100 mg four times daily. 1
The macrocrystal formulation can alternatively be dosed at 50-100 mg four times daily for 5 days, though the twice-daily regimen is preferred for adherence. 1
Treatment duration can range from 3-7 days, though 5 days is the evidence-based standard. 1
Critical Contraindications and Warnings
Avoid nitrofurantoin if early pyelonephritis is suspected, as inadequate tissue penetration may lead to treatment failure. 1
Nitrofurantoin is contraindicated when creatinine clearance is <60 mL/min due to inadequate urinary drug concentrations and increased risk of peripheral neuropathy. 3
In males with UTI, nitrofurantoin has substantially lower efficacy (25% failure rate) compared to females (10-16% failure rate), making it a less optimal choice for men. 3
Common Pitfalls to Avoid
Do not use 3-day regimens despite some UK guidelines recommending this duration—there is insufficient direct evidence supporting 3-day courses, and the established 5-day regimen has superior evidence. 4
Do not extend treatment beyond 7 days unless symptoms persist, as shorter courses minimize adverse effects while maintaining efficacy. 1
For males requiring nitrofurantoin, use 100 mg every 6 hours (four times daily) for 7-14 days, with 14 days recommended when prostatitis cannot be excluded. 3
Side Effect Profile
Nausea and headache are the most commonly reported side effects. 1
Adverse event rates range from 5.6-34% across studies, with gastrointestinal symptoms (nausea 3%, diarrhea 1%) being most frequent. 1, 2
The safety profile is favorable with minimal cross-reactivity with other antibiotic classes. 5
When to Choose Alternatives
If the patient has multiple antibiotic allergies including nitrofurantoin, fosfomycin trometamol 3 g single dose is the preferred alternative. 5
If local E. coli resistance to trimethoprim-sulfamethoxazole is <20%, this becomes a viable 3-day alternative. 1
Reserve fluoroquinolones as last-resort options due to resistance concerns and adverse effect profiles. 1, 5