Standard Dosing of Macrobid (Nitrofurantoin) for Uncomplicated UTIs
The standard dose of Macrobid (nitrofurantoin monohydrate/macrocrystals) is 100 mg orally twice daily for 5 days for the treatment of uncomplicated urinary tract infections. 1, 2
Evidence Supporting the Standard Dosing Regimen
The 2011 Infectious Diseases Society of America (IDSA) and European Society for Microbiology and Infectious Diseases guidelines clearly recommend nitrofurantoin monohydrate/macrocrystals at 100 mg twice daily for 5 days as an appropriate first-line therapy for acute uncomplicated cystitis 1. This recommendation carries an A-I evidence rating, indicating high-quality evidence from well-designed randomized controlled trials.
This dosing recommendation is further supported by:
The American College of Physicians' 2021 best practice advice, which specifically recommends nitrofurantoin for 5 days as a short-course antibiotic option for uncomplicated bacterial cystitis in women 1
The most recent guidelines from 2025 that confirm the standard dose of nitrofurantoin for uncomplicated UTIs remains 100 mg twice daily for 5 days 2
Clinical Efficacy of the Standard Regimen
The 5-day regimen of nitrofurantoin at 100 mg twice daily demonstrates:
- Clinical cure rates of 84-95%
- Microbiological cure rates of 86-92% 2
These outcomes are comparable to other first-line treatments such as 3-day trimethoprim-sulfamethoxazole regimens, making nitrofurantoin an excellent choice for empiric therapy.
Alternative Nitrofurantoin Dosing Options
While the standard remains 100 mg twice daily for 5 days, alternative dosing options that have been used include:
- Nitrofurantoin macrocrystals 50-100 mg four times daily for 5 days 2, 3
- Nitrofurantoin macrocrystals prolonged release at 100 mg twice daily for 5 days 2
Important Considerations
- Nitrofurantoin is contraindicated for upper UTIs (pyelonephritis) as it does not achieve adequate tissue concentrations 2
- Common side effects include nausea (3%) and headache 2
- For uncomplicated UTIs due to vancomycin-resistant enterococci (VRE), a higher frequency dosing of nitrofurantoin 100 mg PO every 6 hours has been recommended 1, though this is not the standard dosing for typical uncomplicated UTIs
Rationale for the 5-Day Duration
The 5-day duration for nitrofurantoin (rather than the 3-day duration used for some other antibiotics like trimethoprim-sulfamethoxazole) is based on pharmacokinetic properties and clinical efficacy studies. Earlier studies with 3-day regimens of nitrofurantoin showed lower efficacy compared to the 5-day regimen 3.
In conclusion, based on the highest quality and most recent evidence, the standard dose of Macrobid (nitrofurantoin monohydrate/macrocrystals) is definitively 100 mg orally twice daily for 5 days for uncomplicated urinary tract infections.