Nitrofurantoin Dosing
For uncomplicated UTIs in women, use nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days as the first-line regimen. 1
Standard Dosing for Uncomplicated UTI in Women
- Nitrofurantoin monohydrate/macrocrystals (Macrobid): 100 mg twice daily for 5-7 days is the IDSA and European Association of Urology recommended first-line treatment 1, 2
- The 5-day regimen is optimal and preferred by both IDSA and European guidelines, balancing efficacy with minimal adverse effects 1
- Alternative formulations include nitrofurantoin macrocrystals 50-100 mg four times daily for 5 days 1
Efficacy Data
- Clinical cure rates range from 88-93% in women with uncomplicated UTI 1, 2
- Bacterial cure rates range from 81-92% 1, 2
- The 5-day nitrofurantoin regimen demonstrates equivalent efficacy to trimethoprim-sulfamethoxazole 3-day regimens 1, 3
Dosing for Men with UTI
- For men: 100 mg twice daily for 7-14 days (14 days recommended when prostatitis cannot be excluded) 4
- Important caveat: Nitrofurantoin has substantially lower efficacy in males, with a 25% failure rate versus 10-16% in females 4
- Consider alternative agents like trimethoprim-sulfamethoxazole 160/800 mg twice daily for 14 days or fluoroquinolones for 5-7 days based on susceptibility testing 4
Pediatric Dosing
- Children ≥12 years: 100 mg twice daily for 7 days 1, 2
- Children <12 years: 5-7 mg/kg/day divided into 4 doses (maximum 100 mg/dose) for 7 days 1, 2
Special Dosing Situations
- For VRE (Vancomycin-resistant Enterococci) UTIs: 100 mg four times daily 1
- For Staphylococcus saprophyticus UTIs: Complete the standard 5-day course of 100 mg twice daily 1
Critical Contraindications and Precautions
- Nitrofurantoin is contraindicated when creatinine clearance is <60 mL/min due to inadequate urinary drug concentrations and increased toxicity risk, including peripheral neuropathy 4, 2
- However, one retrospective study suggests nitrofurantoin may be effective in patients with CrCl 30-60 mL/min when used against susceptible organisms, though this contradicts current guideline recommendations 5
- Do not use if early pyelonephritis is suspected - nitrofurantoin does not achieve adequate tissue concentrations for upper tract infections 1, 4
- Not recommended for complicated UTIs, perinephric abscess, or patients with obstruction, foreign bodies, or incomplete voiding 1, 4
Common Pitfalls to Avoid
- Always check renal function before prescribing - this is the most common and dangerous prescribing error 2
- Do not prescribe for suspected upper tract infections or complicated UTIs 2
- Nausea and headache are the most common side effects, occurring in 5.6-34% of patients 1, 2
Follow-Up Recommendations
- Routine post-treatment cultures are NOT indicated for asymptomatic patients 1, 2
- For women whose symptoms do not resolve by end of treatment or recur within 2 weeks, perform urine culture with susceptibility testing 1, 2
- If retreatment is needed, assume the organism is not susceptible to the original agent and use a different antibiotic for 7 days 2