What is the recommended dosage of Macrobid (Nitrofurantoin) for an uncomplicated urinary tract infection (UTI)?

Macrobid Dosage for Uncomplicated UTI

For uncomplicated urinary tract infections in women, prescribe nitrofurantoin monohydrate/macrocrystals (Macrobid) 100 mg twice daily for 5 days. 1

Standard Dosing Regimen

• Nitrofurantoin monohydrate/macrocrystals: 100 mg orally twice daily for 5-7 days is the IDSA-recommended first-line regimen for uncomplicated cystitis in women 2, 1
• The 5-day duration is optimal and specifically endorsed by both the Infectious Diseases Society of America and European Society for Microbiology and Infectious Diseases 1
• This regimen achieves clinical cure rates of 88-93% and bacterial cure rates of 81-92% 1

Alternative Dosing for Specific Situations

For VRE (vancomycin-resistant enterococci) UTIs:

• Use 100 mg orally four times daily (every 6 hours) 2, 1
• This higher frequency dosing is necessary for resistant organisms 2

Macrocrystal formulation (if monohydrate/macrocrystals unavailable):

• 50-100 mg orally four times daily for 5 days 1

Duration Considerations

• Do not extend treatment beyond 7 days unless symptoms persist, as shorter courses minimize adverse effects while maintaining efficacy 1
• The 5-day regimen has been proven equivalent to trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days in both clinical and microbiological outcomes 1
• Three-day regimens are less well-studied for nitrofurantoin compared to other agents and are not standard 2

Critical Contraindications

Avoid nitrofurantoin if:

• Early pyelonephritis is suspected - nitrofurantoin does not achieve adequate tissue concentrations in the renal parenchyma 1
• Severe renal impairment is present (though mild-moderate reduction in GFR does not preclude use) 3

Common Pitfalls to Avoid

• Do not use single-dose nitrofurantoin - this is statistically less effective than 3-7 day courses 4
• Do not prescribe for complicated UTIs or pyelonephritis - tissue penetration is inadequate for upper tract infections 1
• Do not avoid in mild-moderate renal dysfunction - studies show efficacy is maintained even with estimated GFR around 38 mL/min per 1.73 m² 3

Expected Side Effects

• Nausea and headache are the most common adverse effects 1
• Overall adverse event rates range from 5.6-34% across studies 1

Why Nitrofurantoin is Preferred

• Minimal resistance development and limited collateral damage to normal flora make it an ideal first-line agent 1
• It preserves fluoroquinolones for more serious infections 2, 5
• Single daily dosing options (100 mg twice daily) improve adherence compared to four-times-daily regimens 1