What is the recommended dosage of Macrobid (nitrofurantoin) for a typical adult patient with an uncomplicated urinary tract infection and normal renal function?

Macrobid Dosing for Uncomplicated UTI

For adults with uncomplicated urinary tract infection and normal renal function, prescribe Macrobid (nitrofurantoin monohydrate/macrocrystals) 100 mg twice daily for 5 days. 1, 2, 3

Standard Dosing Regimen

• The Infectious Diseases Society of America (IDSA) and European Association of Urology both recommend 100 mg twice daily for 5 days as the first-line regimen for uncomplicated UTIs in women. 1, 2, 3

• This regimen achieves clinical cure rates of 88-93% and bacterial cure rates of 81-92%. 1, 2, 3

• The 5-day duration is optimal and supported by both American and European guideline societies, balancing efficacy with minimizing adverse effects and resistance. 1, 3

Gender-Specific Considerations

• For men with uncomplicated UTI, extend treatment to 100 mg twice daily for 7 days due to limited observational data suggesting men may require longer courses. 3

• Women should receive the standard 5-day course unless symptoms persist. 1, 3

Critical Renal Function Contraindication

• Nitrofurantoin is absolutely contraindicated when creatinine clearance is <60 mL/min due to inadequate urinary drug concentrations and significantly increased risk of peripheral neuropathy and other toxicities. 2, 3

• Always check renal function before prescribing—this is the most common and dangerous prescribing error with nitrofurantoin. 3

• For patients with CrCl <60 mL/min, switch to trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days (if local resistance <20%) or fosfomycin trometamol 3 g single dose. 2, 3

Alternative Formulations

• Nitrofurantoin macrocrystals can be dosed at 50-100 mg four times daily for 5 days, though the twice-daily Macrobid formulation is preferred for compliance. 1, 3

When NOT to Use Nitrofurantoin

• Do not prescribe if early pyelonephritis is suspected—nitrofurantoin does not achieve adequate tissue concentrations for upper tract infections. 1

• Avoid in complicated UTIs, perinephric abscess, or any suspected upper urinary tract involvement. 1, 3

Common Side Effects and Patient Counseling

• Nausea and headache occur in 5.6-34% of patients and are the most common adverse effects. 1, 3

• Advise adequate hydration during treatment to prevent crystal formation. 1

Follow-Up Algorithm

• Do NOT order routine post-treatment cultures for asymptomatic patients—this is unnecessary and not recommended. 1, 3

• If symptoms do not resolve by end of treatment or recur within 2 weeks, obtain urine culture with susceptibility testing. 1, 3

• For retreatment, assume the organism is not susceptible to nitrofurantoin and use a different antibiotic for 7 days. 3

Pediatric Dosing

• Children ≥12 years: 100 mg twice daily for 7 days. 1, 3

• Children <12 years: 5-7 mg/kg/day divided into 4 doses (maximum 100 mg/dose) for 7 days. 1, 3

Comparative Efficacy Context

• Nitrofurantoin demonstrates equivalent efficacy to trimethoprim-sulfamethoxazole and ciprofloxacin when comparing appropriate duration regimens, but is preferred first-line due to minimal resistance development and limited collateral damage to normal flora. 1, 3