Nitrofurantoin Dosing for Uncomplicated UTI
For adults with uncomplicated UTI and normal renal function, prescribe nitrofurantoin monohydrate/macrocrystals (Macrobid) 100 mg twice daily for 5 days. 1, 2
Standard Dosing Regimen
The recommended dose is 100 mg orally twice daily for 5-7 days, with 5 days being the optimal duration endorsed by both the Infectious Diseases Society of America (IDSA) and the European Society for Microbiology and Infectious Diseases (ESMID). 1, 2
This regimen achieves clinical cure rates of 88-93% and bacterial cure rates of 81-92% for uncomplicated UTIs in women. 1, 2
The 5-day course is equivalent in efficacy to trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days, making it a preferred first-line option. 1
Alternative Dosing Formulations
Nitrofurantoin macrocrystals can be dosed at 50-100 mg four times daily for 5 days, though the twice-daily formulation is preferred for compliance. 1
For vancomycin-resistant Enterococci (VRE) UTIs specifically, increase to 100 mg four times daily. 1
Critical Renal Function Considerations
Nitrofurantoin is contraindicated when creatinine clearance is <60 mL/min due to inadequate urinary drug concentrations and increased risk of peripheral neuropathy and other toxicities. 2
However, one retrospective study suggests nitrofurantoin may be effective in patients with CrCl 30-60 mL/min when used against susceptible organisms, with only 2 of 26 patients failing due to renal insufficiency (both had CrCl <30 mL/min). 3
Despite this single study, guideline recommendations remain firm: avoid nitrofurantoin if CrCl <60 mL/min and consider alternatives like trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days or fosfomycin trometamol 3 g single dose. 2
Important Contraindications and Warnings
Do not use nitrofurantoin if early pyelonephritis is suspected, as it does not achieve adequate tissue concentrations outside the urinary tract. 1
Nitrofurantoin is not appropriate for perinephric abscess or complicated UTIs. 1
Monitor for peripheral neuropathy, pulmonary reactions, and hepatotoxicity, particularly in patients with borderline renal function. 2
Duration Controversy
While UK guidelines suggest 3-day courses, the evidence strongly supports 5-day regimens as the international standard. 1, 4 A 2023 review found little direct evidence supporting 3-day courses, and most major guideline societies (IDSA, ESMID, European Association of Urology) consistently recommend 5 days. 1, 4
Common Side Effects
Nausea and headache are the most frequently reported adverse effects, with overall adverse event rates ranging from 5.6-34%. 1
Ensure adequate hydration during treatment to prevent crystal formation. 1
Special Populations
For men with uncomplicated UTI: Use 7-14 days of therapy based on limited observational data. 1
For women with diabetes and no voiding abnormalities: Treat identically to women without diabetes using the standard 5-day regimen. 1
For children ≥12 years: Use adult dosing of 100 mg twice daily for 7 days. 1