What is the recommended dosing for Macrobid (nitrofurantoin) in an adult patient with an uncomplicated urinary tract infection (UTI) and normal renal function?

Macrobid Dosing for Uncomplicated UTI

For adults with uncomplicated UTI and normal renal function, prescribe Macrobid (nitrofurantoin monohydrate/macrocrystals) 100 mg twice daily for 5 days in women and 7 days in men. 1, 2

Standard Dosing Algorithm

For Women with Uncomplicated Cystitis

• Dose: 100 mg twice daily 1, 2
• Duration: 5 days 1, 2
• Expected efficacy: Clinical cure rates of 88-93% and bacterial cure rates of 81-92% 1, 2

For Men with Uncomplicated UTI

• Dose: 100 mg twice daily 2
• Duration: 7 days (based on limited observational data showing men require longer treatment) 2, 3

Alternative Nitrofurantoin Formulations

If Macrobid is unavailable, alternative formulations include: 1, 2

• Nitrofurantoin macrocrystals: 50-100 mg four times daily for 5 days
• Nitrofurantoin macrocrystals prolonged release: 100 mg twice daily for 5 days

Critical Contraindications - Check Before Prescribing

Renal Function Assessment (MANDATORY)

Never prescribe nitrofurantoin without checking renal function first - this is the most dangerous prescribing error. 2, 3

• Contraindicated if creatinine clearance <60 mL/min per FDA guidance and IDSA recommendations, due to inadequate urinary drug concentrations and increased toxicity risk including peripheral neuropathy 2, 3
• For patients with CrCl 30-60 mL/min, consider alternatives: trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days (if local resistance <20%) or fosfomycin trometamol 3 g single dose 2, 3
• For CrCl <30 mL/min, absolutely avoid nitrofurantoin 3

Clinical Scenario Contraindications

Do not use Macrobid for: 1, 2

• Suspected pyelonephritis or upper tract infections (inadequate renal tissue concentrations)
• Complicated UTIs (structural/functional abnormalities, obstruction, instrumentation)
• Men with suspected prostatitis (inadequate prostatic tissue penetration)
• Pregnancy at term or during labor

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 Considerations

Hydration

• Ensure adequate hydration during treatment to prevent crystal formation 1

Common Side Effects

• Nausea and headache occur in 5.6-34% of patients 1, 2
• Monitor for peripheral neuropathy, pulmonary reactions, and hepatotoxicity, especially in patients with borderline renal function 3

Follow-Up Recommendations

When NOT to Order Post-Treatment Testing

• Do not order routine post-treatment cultures or urinalysis if the patient is asymptomatic 1, 2, 3

When to Obtain Follow-Up Culture

• If symptoms do not resolve by end of treatment or recur within 2 weeks, perform urine culture with susceptibility testing 1, 2, 3
• For retreatment, assume the organism is not susceptible to nitrofurantoin and use a different antibiotic for 7 days 2, 3

Evidence Quality Note

The IDSA, European Association of Urology, and American College of Physicians all consistently recommend the 5-day regimen for women as the optimal balance between efficacy and minimizing antibiotic exposure. 1, 2 This represents a strong consensus across major guideline bodies based on equivalence studies showing nitrofurantoin 5-day regimens match trimethoprim-sulfamethoxazole 3-day regimens in clinical and microbiological cure rates. 1