Macrobid (Nitrofurantoin) Dosing for UTI
For uncomplicated urinary tract infections (UTIs), nitrofurantoin monohydrate/macrocrystals (Macrobid) should be dosed at 100 mg twice daily for 5 days. 1, 2
Standard Dosing Regimen
- The Infectious Diseases Society of America (IDSA) and the European Society for Microbiology and Infectious Diseases recommend nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days as a first-line treatment for uncomplicated UTIs in women 3, 1
- This 5-day regimen has been shown to achieve clinical cure rates of 88-93% and bacterial cure rates of 81-92% 1, 2
- The European Association of Urology also endorses nitrofurantoin as a first-line agent for uncomplicated cystitis with the same dosing recommendation 1
Efficacy Data
- A 5-day course of nitrofurantoin (100 mg twice daily) has demonstrated equivalent efficacy to trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days) in clinical trials 3, 1
- In comparative studies, nitrofurantoin shows clinical cure rates similar to ciprofloxacin and trimethoprim-sulfamethoxazole 1
- Nitrofurantoin achieves early clinical cure rates of approximately 90% and bacterial cure rates of 92% 3
Important Considerations and Contraindications
- Nitrofurantoin is contraindicated in patients with creatinine clearance <60 mL/min due to inadequate urinary drug concentrations and increased risk of toxicity 2
- For patients with renal impairment, alternative agents such as trimethoprim-sulfamethoxazole or fosfomycin trometamol should be considered 2
- Common side effects include nausea and headache, with adverse event rates ranging from 5.6-34% across studies 1
Special Populations
- For male patients with uncomplicated UTIs, a longer duration of 7 days is often used, though evidence is more limited 4
- For women with diabetes but without voiding abnormalities, treatment approach should be similar to women without diabetes 4
Alternative Formulations
- While some countries use different formulations (macrocrystals 50-100 mg four times daily), the monohydrate/macrocrystals formulation at 100 mg twice daily is the standard in the US and most countries 1, 5
Duration Considerations
- Although some UK guidelines suggest 3-day courses, most international guidelines recommend 5 days of therapy 6
- The evidence more strongly supports the 5-day regimen, which balances efficacy with minimizing resistance development 3, 1, 2
Nitrofurantoin remains a valuable first-line agent for uncomplicated UTIs due to its continued effectiveness and low rates of resistance development compared to other antimicrobials 1, 4.