Cephalexin Dosing for Urinary Tract Infections
For uncomplicated urinary tract infections (UTIs), the recommended dose of cephalexin is 500 mg four times daily for 5-7 days. 1, 2
Adult Dosing Recommendations
Uncomplicated UTIs:
- Standard dosing: 500 mg four times daily for 5-7 days 1
- Alternative dosing: 500 mg twice daily for 5-7 days 3, 4
Complicated UTIs:
- Dosing range: 1-4 g daily in divided doses 2
- Duration: 7-14 days 1, 2
- For severe infections, higher doses within the 1-4 g daily range may be needed 2
Special Populations
Renal Impairment:
- Dose adjustment required for patients with creatinine clearance <30 ml/min 5
- Reduction should be proportional to the decreased renal function 5
Pediatric Patients:
- Recommended dosage: 25-50 mg/kg/day in divided doses 2
- For severe infections, dosage may be doubled 2
Clinical Considerations
Efficacy:
- Cephalexin achieves high urinary concentrations (500-1000 μg/ml) following 250-500 mg oral doses 5
- These concentrations far exceed the minimum inhibitory concentration for common urinary pathogens 5
Administration:
- Cephalexin is rapidly absorbed from the upper intestine (not the stomach) 5
- 70-100% of the dose is found in urine within 6-8 hours after administration 5
Treatment Success Rates:
- Recent studies show comparable treatment failure rates between twice-daily (18.7%) and four-times-daily (15.0%) dosing regimens (p=0.465) 4
- For uncomplicated UTIs specifically, failure rates were 14.9% vs 8.1% for twice-daily vs four-times-daily dosing (p=0.197) 4
Common Pitfalls and Caveats
- While the FDA label indicates a dosage of 500 mg every 12 hours for uncomplicated cystitis 2, current UTI treatment guidelines specifically recommend 500 mg four times daily 1
- Twice-daily dosing may be considered to improve adherence, as recent research suggests similar efficacy to four-times-daily dosing 3, 4
- Ensure adequate treatment duration (5-7 days for uncomplicated UTIs, 7-14 days for complicated UTIs) 1, 2
- For infections requiring more than 4 g daily, consider parenteral cephalosporins 2
- Obtain urine culture before starting antibiotics to guide targeted therapy 1