Cephalexin 250mg Daily for UTI Prevention
Cephalexin 250mg daily is a reasonable option for UTI prophylaxis in women with recurrent UTIs, though it is not considered a first-line agent and the evidence supporting this specific dose is limited. 1
Guideline Support for Cephalexin in UTI Prevention
Cephalexin is explicitly listed as an acceptable antimicrobial for continuous prophylaxis in women with recurrent UTIs by both the Society of Obstetricians and Gynaecologists of Canada and the European Association of Urology guidelines. 1 These guidelines recommend continuous daily antibiotic prophylaxis for 6-12 months when non-antimicrobial measures have failed. 1
The recommended antimicrobials for prophylaxis include trimethoprim-sulfamethoxazole, trimethoprim, nitrofurantoin, cefaclor, cephalexin, norfloxacin, ciprofloxacin, and fosfomycin. 1
Evidence for Low-Dose Cephalexin
A placebo-controlled trial demonstrated that cephalexin 125mg nightly was superior to placebo in reducing UTIs over 12 months, with greater reduction in the cephalexin group during 6-month follow-up (p <0.01). 1 This study had fair quality evidence (2B rating). 1
Importantly, a 1975 study specifically evaluated cephalexin 250mg daily as a single evening dose for long-term UTI prevention in elderly patients (average age 78 years). 2 The urine remained free of bacteriuria in 50% of patients treated with cephalexin, with a bacteriuria-free interval averaging 92 days. 2 Notably, cephalexin 125mg was found to be as effective as 250mg in this study. 2
Important Caveats and Considerations
Before initiating prophylaxis, eradication of any existing UTI must be confirmed with a negative urine culture 1-2 weeks after treatment. 1 This is a critical step that should never be skipped.
Antimicrobial prophylaxis should only be considered after counseling and behavioral modifications have been attempted. 1 Non-antimicrobial strategies should be the first approach.
The choice of antimicrobial should be based on the identification and susceptibility pattern of organisms causing the patient's previous UTIs and any drug allergies. 1
Resistance Concerns
A significant concern with cephalexin prophylaxis is the development of antimicrobial resistance. In one study of catheterized patients with asymptomatic bacteriuria treated with cephalexin, 47% of reinfecting organisms in the cephalexin group were highly resistant to cephalexin, compared to only 26% in the control group. 1 This underscores the importance of judicious use and regular reassessment.
Practical Limitations
The evidence quality for cephalexin prophylaxis is rated as "poor to fair" (2B level) in systematic reviews. 1 Most studies on UTI prophylaxis suffer from small sample sizes, lack of blinding, and inadequate power. 1
Cephalexin is not recommended for asymptomatic bacteriuria in catheterized patients, spinal cord injury patients, or those with neurogenic bladders, as treatment does not reduce subsequent UTI rates and promotes resistance. 1
Dosing Recommendation
While 250mg daily has been studied, the more commonly cited dose in guidelines is 125mg nightly, which appears equally effective based on available evidence. 1, 2 The 250mg dose may be appropriate if local resistance patterns or patient factors warrant higher dosing, but this should be balanced against resistance concerns.