What is the recommended dose of Macrobid (nitrofurantoin) for treating urinary tract infections (UTIs)?

Macrobid Dosing for UTI

For uncomplicated urinary tract infections in women, the recommended dose of Macrobid (nitrofurantoin monohydrate/macrocrystals) is 100 mg twice daily for 5 days. 1, 2

Standard Dosing Regimens

First-Line Treatment in Women

• Nitrofurantoin monohydrate/macrocrystals (Macrobid): 100 mg twice daily for 5 days is the preferred first-line regimen recommended by both the Infectious Diseases Society of America and the European Association of Urology 1, 2, 3
• Alternative nitrofurantoin formulations include:
  • Nitrofurantoin macrocrystals: 50-100 mg four times daily for 5 days 1
  • Nitrofurantoin macrocrystals prolonged release: 100 mg twice daily for 5 days 1

Treatment Duration Considerations

• The 5-day regimen is optimal and consistently recommended across major guidelines, balancing efficacy with minimizing adverse effects and resistance development 2, 3
• A 7-day course may be considered for treatment failures or when symptoms persist, but should not routinely exceed 7 days 2
• The UK's 3-day recommendation lacks direct supporting evidence and is not endorsed by major international guidelines 4

Treatment in Men

• For men with uncomplicated UTI, use 100 mg twice daily for 7 days based on limited observational data 2
• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 7 days is an alternative first-line option in men 1

Efficacy Data

• Clinical cure rates range from 88-93% for uncomplicated UTIs in women 2
• Bacterial cure rates range from 81-92% 2
• Nitrofurantoin demonstrates equivalent efficacy to trimethoprim-sulfamethoxazole and ciprofloxacin when comparing appropriate duration regimens 2

Critical Contraindications and Precautions

Renal Function

• Nitrofurantoin is contraindicated when creatinine clearance is <60 mL/min due to inadequate urinary drug concentrations and increased toxicity risk, including peripheral neuropathy 5
• For patients with CrCl <60 mL/min, consider alternative agents such as trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days or fosfomycin trometamol 3 g single dose 5
• One small study suggested possible efficacy with CrCl 30-60 mL/min, but this contradicts guideline recommendations and should not change practice 6

Clinical Situations Where Nitrofurantoin Should NOT Be Used

• Do not use if pyelonephritis is suspected (upper tract infection) 2
• Avoid in patients with perinephric abscess 2
• Not recommended in pregnancy (first trimester concerns with trimethoprim alternatives) 1

Special Populations

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 2

Vancomycin-Resistant Enterococci (VRE)

• For VRE uncomplicated UTIs: 100 mg four times daily 2

Follow-Up Recommendations

• Routine post-treatment cultures are NOT indicated for asymptomatic patients 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 1

Common Pitfalls to Avoid

• Do not prescribe nitrofurantoin without checking renal function - this is the most common and dangerous error 5
• Do not use for complicated UTIs or suspected upper tract infections 2
• Do not extend treatment beyond 7 days unless symptoms persist, as this increases adverse effects without improving efficacy 2
• Be aware that nausea and headache are the most common side effects, occurring in 5.6-34% of patients 2