Nitrofurantoin Dosing for Pyuria and Dysuria
For adults with uncomplicated lower urinary tract infection presenting with pyuria and dysuria, prescribe nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days. 1
Standard Dosing Regimen
Nitrofurantoin 100 mg orally twice daily for 5 days is the first-line recommendation from the Infectious Diseases Society of America (IDSA) and European Association of Urology for uncomplicated UTI in women. 1
This 5-day regimen achieves clinical cure rates of 88-93% and bacterial cure rates of 81-92%. 1, 2
The 5-day course is equivalent to trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days) in both clinical and microbiological outcomes. 1
Alternative Dosing Considerations
Nitrofurantoin macrocrystals can be dosed at 50-100 mg four times daily for 5 days as an alternative formulation, though twice-daily dosing improves adherence. 1
For vancomycin-resistant Enterococci (VRE) UTIs specifically, increase to 100 mg four times daily. 1
Duration: Why 5 Days, Not 3 Days
Avoid 3-day courses of nitrofurantoin—clinical efficacy drops significantly to only 61-70% with 3-day regimens compared to 79-92% with 5-7 day courses. 3
While UK guidelines promote 3-day courses, there is little direct evidence supporting this shorter duration, and international guidelines consistently recommend 5 days. 1, 4
The IDSA and European Society for Microbiology and Infectious Diseases both specifically endorse 5 days as the optimal duration. 1
Critical Contraindications
Do not use nitrofurantoin if creatinine clearance is <60 mL/min—inadequate urinary drug concentrations occur and risk of peripheral neuropathy and other toxicities increases substantially. 2, 5
Avoid nitrofurantoin if early pyelonephritis is suspected (fever, flank pain, costovertebral angle tenderness)—it does not achieve adequate tissue concentrations for upper tract infections. 1, 5
Special Population: Males
For males with UTI, use nitrofurantoin 100 mg every 6 hours (four times daily) for 7-14 days, not the standard twice-daily dosing used in women. 5
Extend to 14 days when prostatitis cannot be excluded clinically. 5
Be aware that nitrofurantoin has substantially lower efficacy in males (25% failure rate) compared to females (10-16% failure rate), so consider alternative agents like trimethoprim-sulfamethoxazole or fluoroquinolones based on susceptibility testing. 5
Expected Clinical Response
Patients should show symptomatic improvement within 48-72 hours—if symptoms persist or worsen, obtain urine culture with susceptibility testing and consider alternative diagnosis or resistant organism. 5
Combined symptomatic improvement and bacteriological cure occurs in approximately 77% of patients by day 3 and 88% by day 7. 6
In a head-to-head trial, nitrofurantoin 100 mg three times daily for 5 days achieved 70% clinical resolution at 28 days compared to 58% with single-dose fosfomycin, demonstrating superior efficacy. 7
Common Pitfalls to Avoid
Do not routinely order post-treatment urine cultures in asymptomatic patients—this leads to unnecessary treatment of asymptomatic bacteriuria. 1
Do not extend treatment beyond 7 days unless symptoms persist—longer courses increase adverse effects without improving efficacy. 1
For women whose symptoms do not resolve by end of treatment or recur within 2 weeks, obtain urine culture and consider retreatment with a 7-day regimen using a different agent. 1
Adverse Effects
Nausea and headache are most common, occurring in 5-16% of patients. 1, 3
Gastrointestinal side effects (nausea in 3%, diarrhea in 1%) are mild, reversible, and do not typically require discontinuation. 3, 7
Serious hypersensitivity reactions (pulmonary fibrosis, hepatotoxicity) are exceedingly rare with short-term use. 3