What is the recommended dose of nitrofurantoin (antibiotic) for an uncomplicated urinary tract infection (UTI)?

Nitrofurantoin Dosing for Uncomplicated UTI

For uncomplicated urinary tract infections in women, prescribe nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days. 1

Standard Dosing Regimen

• The recommended dose is nitrofurantoin monohydrate/macrocrystals 100 mg orally twice daily for 5-7 days, with 5 days being the preferred duration based on current IDSA and European guidelines 2, 1
• The 5-day regimen achieves clinical cure rates of 84-90% and bacterial cure rates of 92%, which are equivalent to trimethoprim-sulfamethoxazole 2, 3
• At 30-day follow-up, clinical cure rates remain robust at 84% with the 5-day course 2, 3

Evidence Supporting 5-Day Duration

The shift from traditional 7-day courses to 5-day regimens is supported by high-quality randomized controlled trial data:

• A landmark 2007 RCT directly compared 5-day nitrofurantoin (100 mg twice daily) versus 3-day trimethoprim-sulfamethoxazole, demonstrating equivalent efficacy with 90% clinical cure at early follow-up and 84% at 30 days 2, 3
• Earlier studies using 7-day regimens showed similar efficacy (89-93% clinical cure), suggesting no additional benefit from extending treatment beyond 5 days 2
• The 5-day duration balances optimal efficacy while minimizing adverse effects and selective pressure for resistance 1

Alternative Dosing for Specific Situations

For vancomycin-resistant enterococcal (VRE) UTIs specifically, increase frequency to 100 mg four times daily (every 6 hours) 1, 4

The older macrocrystal formulation can be dosed at 50-100 mg four times daily for 5 days, though the monohydrate/macrocrystal formulation at twice-daily dosing is preferred for adherence 1

Critical Contraindications and Precautions

• Do not prescribe nitrofurantoin if creatinine clearance is <60 mL/min due to inadequate urinary drug concentrations and increased toxicity risk 4
• Avoid nitrofurantoin if early pyelonephritis is suspected, as it does not achieve adequate tissue concentrations for upper tract infections 1, 4
• Common adverse effects include nausea and headache, occurring in 5.6-34% of patients 2, 1

When to Consider Alternative Agents

If nitrofurantoin cannot be used, first-line alternatives include:

• Fosfomycin trometamol 3 g as a single dose (slightly lower efficacy but excellent for adherence) 1
• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days only if local E. coli resistance is <20% 2, 1

Follow-Up Recommendations

• Routine post-treatment urine cultures are not indicated for asymptomatic patients 1, 4
• If symptoms persist or recur within 2 weeks, obtain urine culture with susceptibility testing and consider retreatment with a 7-day course of an alternative agent 1

Common Pitfall to Avoid

Do not use the 3-day duration commonly promoted in some UK guidelines 5. While 3-day courses are effective for other agents, there is insufficient direct evidence supporting 3-day nitrofurantoin regimens for uncomplicated UTI 5. The evidence base consistently supports 5-7 day courses, with 5 days being the optimal balance 2, 1, 3.