What is the recommended dose of Nitrofurantoin (antibiotic) for urinary tract infections (UTIs)?

Nitrofurantoin Dosing for Urinary Tract Infections

The recommended dose of nitrofurantoin for uncomplicated urinary tract infections is 100 mg twice daily for 5 days, which has demonstrated a clinical cure rate of 90% and bacterial eradication rate of 92%. 1

Dosing Recommendations

First-line Treatment

• Nitrofurantoin 100 mg twice daily for 5 days
  • High efficacy with approximately 2% resistance rate compared to other antimicrobials
  • American College of Physicians recommends as first-line treatment 1
  • Short-course therapy (≤6 days) is as effective as longer treatment with fewer adverse events 1

Alternative Dosing Regimens

• While the current UK guidelines recommend a 3-day course of nitrofurantoin 100 mg twice daily, there is limited direct evidence supporting this shorter duration 2
• Older studies used nitrofurantoin 50 mg four times daily for 7 days 3
• For prophylaxis in recurrent UTIs, a single 100 mg dose in the evening has been studied 4

Contraindications and Precautions

• Nitrofurantoin is contraindicated in:
  • Patients with significant renal impairment (creatinine clearance <30 mL/min)
  • Pregnant women in their third trimester
  • Patients with G6PD deficiency 1

Adverse Effects

• Incidence of adverse effects is approximately 28%
• Primarily gastrointestinal, including nausea and diarrhea 1
• Side effects are generally mild and transient 3

Clinical Efficacy

• Nitrofurantoin has demonstrated significant superiority over placebo:
  • In bacteriologically proven UTI, nitrofurantoin achieved bacterial cure in 21/26 patients after 3 days compared to 5/25 with placebo (NNT = 1.6) 5
  • Combined symptomatic improvement and cure after 3 days was 27/35 in the nitrofurantoin group versus 19/35 in the placebo group 5

Alternative Treatment Options

If nitrofurantoin is contraindicated, consider:

• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days (only if local resistance <20% and not used in previous 3 months) 1
• Fosfomycin 3g single dose (comparable efficacy to nitrofurantoin with similar clinical and microbiological cure rates) 6
• Ciprofloxacin should be reserved for cases where first-line options cannot be used due to resistance concerns 1

Monitoring and Follow-up

• No routine post-treatment urinalysis or cultures are needed if symptoms resolve 1
• If symptoms don't improve within 72 hours, reevaluate with urine culture 1

Common Pitfalls to Avoid

1. Inappropriate use in renal impairment: Always check creatinine clearance before prescribing; avoid if <30 mL/min
2. Overtreatment: Stick to the recommended 5-day course for uncomplicated UTIs; longer courses increase adverse effects without improving outcomes
3. Ignoring local resistance patterns: While nitrofurantoin generally has low resistance rates (2%), local patterns may vary
4. Missing complicated UTI: Ensure the infection is truly uncomplicated before prescribing standard dosing