Cephalexin Dosing for Urinary Tract Infections (UTIs)
For uncomplicated UTIs in adults, cephalexin should be dosed at 500 mg orally every 12 hours for 7-14 days. 1
Adult Dosing Recommendations
Uncomplicated UTIs
- 500 mg orally every 12 hours for 7-14 days 2, 1
- Alternative dosing: 250 mg orally every 6 hours for 7-14 days 1
- Total daily dose should remain within 1-4 grams per day 1
Complicated UTIs (including all male UTIs)
- 500 mg orally every 6 hours (or 1 g every 12 hours) for 7-14 days 3, 1
- Male UTIs are always considered complicated and require the full 7-14 day treatment course 3
Pediatric Dosing Recommendations
- Standard dose: 25-50 mg/kg/day divided into 4 doses 2, 1
- For severe infections: dosage may be doubled 1
- For otitis media: 75-100 mg/kg/day in 4 divided doses 1
Dosing in Renal Impairment
- For creatinine clearance <30 mL/min: reduce dose proportionally to decreased renal function 4
- Dose adjustment can be based on creatinine clearance or serum creatinine levels 4
Clinical Considerations
Efficacy
- Recent research shows that twice-daily dosing (500 mg BID) is as effective as four-times-daily dosing for uncomplicated UTIs in women 5
- Treatment failure rates were similar between twice-daily and four-times-daily regimens (12.7% vs 17%, respectively) 5
Duration of Therapy
- For uncomplicated cystitis: 7-14 days of therapy is recommended 2, 1
- For complicated UTIs: full 7-14 days of therapy is necessary 3
- For streptococcal infections: minimum 10-day course 1
Administration
- Cephalexin can be administered without regard to meals 1
- For patients who have difficulty with adherence, twice-daily dosing may improve compliance while maintaining efficacy 5, 6
Monitoring
- Obtain urine culture before starting therapy 3
- Consider follow-up cultures after completion of therapy to confirm eradication, especially in complicated cases 3
- Monitor for treatment failure, which may indicate resistant organisms or underlying anatomical abnormalities 3
Caveats and Pitfalls
- If daily doses greater than 4 g are required, consider switching to parenteral cephalosporins 1
- Cephalexin is not recommended for severe infections requiring high serum concentrations 1
- For patients with cephalexin-resistant organisms, alternative antibiotics should be considered based on culture results 7
- Nitrofurantoin should not be used for febrile UTIs or pyelonephritis as it doesn't achieve adequate tissue concentrations 2
- Always consider local resistance patterns when selecting empiric therapy 2