From the Guidelines
Nitrofurantoin and trimethoprim are commonly prescribed for urinary tract infections (UTIs) because they concentrate effectively in the urinary tract and target the bacteria that typically cause these infections.
Key Points
- Nitrofurantoin (typically dosed as 100mg twice daily for 5 days) and trimethoprim (usually 100mg twice daily for 3 days) are effective against common UTI pathogens like E. coli.
- Nitrofurantoin is preferred for uncomplicated lower UTIs due to low resistance rates and minimal impact on gut flora, though it shouldn't be used in patients with poor kidney function (CrCl <30 mL/min) or for upper UTIs.
- Trimethoprim is often combined with sulfamethoxazole (as co-trimoxazole) for broader coverage but can be used alone, especially in patients with sulfa allergies.
- These antibiotics are chosen based on their targeted action in the urinary system, relatively narrow spectrum to minimize resistance development, and generally good safety profiles when prescribed appropriately, as supported by studies such as 1.
Evidence Summary
Studies have shown that nitrofurantoin and trimethoprim-sulfamethoxazole are effective treatments for acute uncomplicated cystitis in women, with cure rates ranging from 79% to 95% 1. The choice between nitrofurantoin and trimethoprim-sulfamethoxazole depends on local resistance rates and patient factors, such as kidney function and sulfa allergy status. Recent guidelines recommend short-course antibiotics with either nitrofurantoin for 5 days, trimethoprim-sulfamethoxazole for 3 days, or fosfomycin as a single dose for uncomplicated cystitis in women 1. It's essential to consider local resistance patterns and patient-specific factors when selecting an antibiotic for UTI treatment, as emphasized by 1.
From the Research
Rationale for Nitrofurantoin and Trimethoprim in UTI Treatment
- Nitrofurantoin is recommended as a first-line empiric antibiotic therapy for acute uncomplicated bacterial cystitis in otherwise healthy adult nonpregnant females due to its efficacy and safety profile 2, 3, 4.
- Trimethoprim-sulfamethoxazole was traditionally used as a first-line treatment for acute uncomplicated UTI, but increasing resistance among community-acquired Escherichia coli has led to a reassessment of its use 3.
- Nitrofurantoin has been shown to be effective in preventing UTIs, with a risk ratio of 0.38 in favor of nitrofurantoin compared to no prophylaxis 5.
- The choice of agent for treating uncomplicated UTIs should be based on pharmacokinetic characteristics to optimize clinical benefit and minimize the risk of antibacterial resistance 4.
Antibiotic Susceptibility and Resistance
- All-pathogen susceptibilities to nitrofurantoin were 64.1%, while sulfamethoxazole/trimethoprim had a susceptibility of 50.5% 6.
- Non-ESBL E. coli susceptibilities to nitrofurantoin were 90.0%, and to sulfamethoxazole/trimethoprim were 83.3% 6.
- High rates of resistance to trimethoprim-sulfamethoxazole and ciprofloxacin preclude their use as empiric treatment of UTIs in several communities 2.
Treatment Guidelines
- Nitrofurantoin and amoxicillin/clavulanate are appropriate first-line options for empiric treatment of symptomatic cystitis, with sulfamethoxazole/trimethoprim as an alternative 6.
- The use of nitrofurantoin and trimethoprim-sulfamethoxazole should be guided by local susceptibility patterns and patient-specific factors to ensure effective treatment and minimize resistance development 2, 3, 4.