Macrodantin (Nitrofurantoin) Dosing for Urinary Tract Infections
Recommended Dosing for Women with Uncomplicated Cystitis
For uncomplicated UTIs in women, use nitrofurantoin macrocrystals 100 mg twice daily for 5 days as first-line therapy. 1, 2
Standard Dosing Options
The European Association of Urology guidelines provide three equivalent first-line regimens for women 1:
- Nitrofurantoin monohydrate or macrocrystals: 100 mg twice daily for 5 days 1, 2
- Nitrofurantoin macrocrystals: 50-100 mg four times daily for 5 days 1, 2
- Nitrofurantoin macrocrystals prolonged release: 100 mg twice daily for 5 days 1, 2
The 5-day regimen achieves clinical cure rates of 88-93% and bacterial cure rates of 81-92% in women with uncomplicated UTIs 2. This duration is supported by both the Infectious Diseases Society of America and European Society for Microbiology and Infectious Diseases 2.
Clinical Efficacy Evidence
Nitrofurantoin demonstrates superior efficacy compared to placebo, with combined symptomatic improvement and bacteriological cure achieved in 77% of treated patients versus 54% with placebo at 3 days (NNT = 4.4) 3. The bacteriological cure rate at 3 days is 81% with nitrofurantoin versus 20% with placebo 3.
Dosing for Men with UTI
For men with uncomplicated UTI, use nitrofurantoin 100 mg every 6 hours (four times daily) for 7-14 days, with 14 days recommended when prostatitis cannot be excluded. 4
Critical Caveat for Male Patients
Nitrofurantoin has substantially lower efficacy in males, with a 25% failure rate compared to 10-16% in females. 4 Consider alternative agents such as trimethoprim-sulfamethoxazole 160/800 mg twice daily for 14 days or fluoroquinolones based on susceptibility testing 4.
Special Dosing Situations
Vancomycin-Resistant Enterococci (VRE)
For uncomplicated UTIs caused by VRE, use 100 mg four times daily 2.
Pediatric Dosing
- Children ≥12 years: 100 mg twice daily for 7 days 2
- 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 2
Absolute Contraindications
Do not use nitrofurantoin in the following situations:
- Creatinine clearance <60 mL/min (inadequate urinary drug concentrations and increased risk of peripheral neuropathy) 4
- Suspected early pyelonephritis 2, 4
- Perinephric abscess 2
Treatment Failure Management
If symptoms do not resolve by the end of treatment or recur within 2 weeks, obtain urine culture with antimicrobial susceptibility testing. 1, 2 Assume the organism is not susceptible to nitrofurantoin and retreat with a 7-day regimen using a different agent 1, 2.
Do not perform routine post-treatment urinalysis or urine cultures in asymptomatic patients 2.
Common Adverse Effects
Nausea and headache are the most frequently reported side effects, occurring in 5.6-34% of patients 2. Severe adverse effects (such as interstitial pneumonia) occur infrequently at rates of 0.02-1.5 per 1000 users 5. The risk of severe toxicity increases with prolonged prophylactic use 5.
Comparative Efficacy
Nitrofurantoin demonstrates equivalent efficacy to trimethoprim-sulfamethoxazole when comparing 5-day nitrofurantoin regimens to 3-day trimethoprim-sulfamethoxazole regimens, with both achieving approximately 90% clinical cure rates 2. Seven-day regimens of nitrofurantoin show similar clinical cure rates to ciprofloxacin and trimethoprim-sulfamethoxazole 2.