Macrobid Dosing for Uncomplicated UTI
For uncomplicated urinary tract infections, prescribe nitrofurantoin monohydrate/macrocrystals (Macrobid) 100 mg twice daily for 5 days. 1
Standard Dosing Regimen
- The recommended dose is 100 mg orally twice daily for 5 days for uncomplicated UTIs in women, as endorsed by the Infectious Diseases Society of America (IDSA) and the European Society for Microbiology and Infectious Diseases (ESMID) 1, 2
- This 5-day regimen achieves clinical cure rates of 88-93% and bacterial cure rates of 81-92% 1, 2
- The 5-day course is equivalent in efficacy to trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days 1
Alternative Dosing for Specific Situations
- For men with uncomplicated UTI: Use 100 mg twice daily for 7 days (extended duration due to higher risk of tissue involvement) 3
- For VRE (vancomycin-resistant enterococci) UTIs: Use 100 mg four times daily (not twice daily) 4, 1
- For UTI prophylaxis: Use 50 mg once daily at bedtime 3
Critical Contraindication: Renal Function
Do not prescribe nitrofurantoin if creatinine clearance is <60 mL/min due to inadequate urinary drug concentrations and increased risk of peripheral neuropathy and other toxicities 2
- This contraindication applies regardless of the severity of renal impairment 2
- For patients with CrCl <60 mL/min, switch to trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days or fosfomycin trometamol 3 g single dose 2
- Important caveat: One study in older women suggested that mild-to-moderate renal impairment may not justify complete avoidance, but current guidelines maintain the CrCl <60 mL/min contraindication 5, 2
When NOT to Use Nitrofurantoin
Avoid nitrofurantoin if early pyelonephritis is suspected, as it does not achieve adequate tissue concentrations outside the urinary tract 1
- Signs suggesting pyelonephritis include fever, flank pain, costovertebral angle tenderness, or systemic symptoms 1
- In these cases, use fluoroquinolones or beta-lactams with better tissue penetration 1
Common Pitfalls to Avoid
- Do not use the macrocrystal formulation (not Macrobid) at 100 mg twice daily - the standard macrocrystal formulation requires 50-100 mg four times daily for 5 days due to different pharmacokinetics 1
- Do not extend treatment beyond 7 days unless symptoms persist, as longer courses increase adverse effects without improving efficacy 1
- Do not adjust dose for renal function - instead, avoid the drug entirely if CrCl <60 mL/min 2
- Do not use in the last trimester of pregnancy (after 38 weeks gestation) due to risk of hemolytic anemia in the newborn 6
Monitoring and Follow-Up
- Routine post-treatment urinalysis or urine cultures are not indicated for asymptomatic patients 1
- If symptoms do not resolve by day 5 or recur within 2 weeks, obtain urine culture with susceptibility testing and consider retreatment with a 7-day course of an alternative agent 1
- Monitor for adverse effects including nausea and headache (most common, occurring in 5.6-34% of patients) 1