Macrobid Dosing for Uncomplicated UTI
For uncomplicated urinary tract infections in women, prescribe Macrobid (nitrofurantoin monohydrate/macrocrystals) 100 mg orally twice daily for 5 days. 1, 2
Standard Dosing Regimen
The 5-day regimen (100 mg twice daily) is the preferred duration recommended by both the Infectious Diseases Society of America (IDSA) and the European Society for Microbiology and Infectious Diseases (ESMID) for uncomplicated UTIs in women. 1, 2
This regimen achieves clinical cure rates of 84-90% and bacterial cure rates of 92% at early follow-up (5-9 days post-treatment), with sustained clinical cure rates of 84% at 30-day follow-up. 2
A 7-day course (100 mg twice daily) is an acceptable alternative with clinical cure rates of 89-93% and bacterial cure rates of 86%, showing equivalent efficacy to ciprofloxacin and trimethoprim-sulfamethoxazole. 2
Critical Contraindications
Do not use nitrofurantoin if creatinine clearance is <60 mL/min, as inadequate urinary drug concentrations prevent bactericidal activity and increase toxicity risk. 2, 3
Avoid nitrofurantoin if early pyelonephritis is suspected, as it does not achieve adequate tissue concentrations for upper tract infections. 1, 3
Nitrofurantoin is contraindicated in the last trimester of pregnancy. 4
Special Dosing Situations
For vancomycin-resistant Enterococcus (VRE) UTIs: Use 100 mg orally four times daily (every 6 hours) rather than the standard twice-daily dosing. 1, 3
For children ≥12 years: Use the adult dose of 100 mg twice daily for 7 days. 1, 2
For children <12 years: Use 5-7 mg/kg/day divided into 4 doses (maximum 100 mg/dose) for 7 days. 1, 2
Common Pitfalls to Avoid
Do not prescribe 3-day regimens (100 mg four times daily for 3 days), as these show inferior efficacy with only 88% clinical cure and 74% bacterial cure rates compared to 5-day regimens. 2
Do not use in patients with any degree of renal impairment (CrCl <60 mL/min) per current IDSA guidelines, despite some retrospective data suggesting efficacy in CrCl 30-60 mL/min range. 2, 5
Verify the patient does not have complicating factors such as suspected pyelonephritis, perinephric abscess, or upper tract involvement, as nitrofurantoin is ineffective for these conditions. 1, 3
Expected Adverse Effects
Nausea and headache are the most common side effects, occurring in 5.6-34% of patients depending on the study. 1, 2
Serious adverse effects such as pulmonary reactions and polyneuropathy mainly occur with long-term use, not with short-course therapy. 4
Follow-Up Recommendations
Routine post-treatment urinalysis or urine cultures are not indicated for asymptomatic patients. 1
For women whose symptoms do not resolve by the end of treatment or recur within 2 weeks, perform a urine culture with susceptibility testing and consider retreatment with a 7-day regimen using another agent. 1, 3
Alternative First-Line Options When Nitrofurantoin Cannot Be Used
Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days if local E. coli resistance is <20% or if the infecting strain is confirmed susceptible. 1, 2
Fosfomycin trometamol 3 g single dose is an alternative with slightly lower efficacy (90% vs 95% clinical cure for nitrofurantoin). 1, 2
Pivmecillinam 400 mg twice daily for 5 days where available. 1