What is the recommended dosing for Macrobid (nitrofurantoin) in the treatment of acute uncomplicated urinary tract infections (UTIs)?

Macrobid Dosing for Acute Uncomplicated UTI

For acute uncomplicated UTI in women, prescribe Macrobid (nitrofurantoin monohydrate/macrocrystals) 100 mg orally twice daily for 5 days. 1, 2

Standard Dosing Algorithm

For Women with Uncomplicated Cystitis

• First-line regimen: 100 mg twice daily for 5 days 1, 2

  • This achieves clinical cure rates of 84-90% and bacterial cure rates of 92% at early follow-up 2
  • The 5-day regimen is equivalent to trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days 1
  • Both IDSA and European guidelines consistently recommend this as the optimal duration 1, 2

• Alternative 7-day regimen: 100 mg twice daily for 7 days 2

  • Use if patient has borderline complicated features or you want maximum efficacy 2
  • Achieves clinical cure rates of 89-93% and bacterial cure rates of 86% 2
  • Shows equivalent efficacy to ciprofloxacin and trimethoprim-sulfamethoxazole when comparing similar duration courses 2

• Avoid 3-day regimens (100 mg four times daily) 2

  • Lower efficacy with only 88% clinical cure and 74% bacterial cure rates 2

For Men with Uncomplicated UTI

• Prescribe 100 mg twice daily for 7 days 3
  • Men require longer treatment duration based on observational data 3
  • Expected clinical cure rates of 88-93% 3

For Special Populations

• VRE (vancomycin-resistant Enterococcus) UTIs: 100 mg four times daily 1, 2
• 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

Critical Contraindications - Check Before Prescribing

Always check renal function first - this is the most dangerous error to avoid 3

• Absolute contraindication: CrCl <60 mL/min per FDA and IDSA guidelines 2, 3

  • Inadequate urinary drug concentrations prevent bactericidal activity 2
  • Increased risk of peripheral neuropathy and other toxicity 3
  • Switch to trimethoprim-sulfamethoxazole or fosfomycin instead 2

• Do not use if early pyelonephritis is suspected 1, 2

  • Nitrofurantoin does not achieve adequate tissue concentrations for upper tract infections 2, 3

• Contraindicated in last trimester of pregnancy 4

• Avoid in patients with intrinsically resistant organisms 5

  • Do not use for Proteus species, Pseudomonas, or Serratia 5

When to Choose Alternative First-Line Agents

• If CrCl 30-60 mL/min: Use trimethoprim-sulfamethoxazole 160/800 mg twice daily for 7 days (if local resistance <20%) or fosfomycin 3 g single dose 2, 3

• If sulfa allergy and normal renal function: Nitrofurantoin remains first-line 1

• If local E. coli resistance to TMP-SMX <20%: TMP-SMX 160/800 mg twice daily for 3 days is equivalent alternative 2

• If patient prefers single-dose therapy: Fosfomycin 3 g single dose (slightly lower efficacy: 90% vs 95% clinical cure) 2

Expected Adverse Effects

• Most common: Nausea and headache 1, 2

  • Occur in 5.6-34% of patients depending on the study 2
  • Rates comparable to trimethoprim-sulfamethoxazole (31-38%) 2

• Monitor for serious reactions in borderline renal function: 3

  • Peripheral neuropathy
  • Pulmonary reactions
  • Hepatotoxicity

Follow-Up Recommendations

• Do not order routine post-treatment cultures if patient is asymptomatic 1, 3

• If symptoms persist or recur within 2 weeks: 1, 3

  • Obtain urine culture with susceptibility testing
  • Assume resistance to nitrofurantoin
  • Retreat with a different antibiotic for 7 days

Common Pitfalls to Avoid

• Never prescribe without checking renal function first - especially critical in elderly patients 3
• Do not use for complicated UTIs or suspected pyelonephritis - tissue penetration is inadequate 3
• Avoid in patients with alkaline urine - reduces drug efficacy 5
• Do not extend treatment beyond 7 days unless symptoms persist - minimizes adverse effects while maintaining efficacy 1