What is the typical dose of cephalexin (cephalexin) for an adult with a urinary tract infection (UTI)?

Cephalexin Dosing for Urinary Tract Infections in Adults

For uncomplicated UTIs in adults, the recommended dose of cephalexin is 500 mg four times daily for 5-7 days. 1

Dosing Recommendations

The FDA-approved dosing for cephalexin in UTIs includes:

• Standard adult dose: 500 mg every 12 hours for uncomplicated cystitis 2
• Duration: 7-14 days for cystitis therapy 2
• Alternative dosing: 500 mg four times daily for 5-7 days 1

Recent evidence suggests that twice-daily dosing may be as effective as four-times-daily dosing:

• A 2023 retrospective study found no significant difference in treatment failure between cephalexin 500 mg twice daily versus 500 mg four times daily for uncomplicated UTIs in women (12.7% vs 17%, p=0.343) 3

Considerations for Specific Populations

Renal Impairment

• Patients with creatinine clearance <30 mL/min require dose reduction proportional to reduced kidney function 4
• Consider monitoring renal function in elderly patients or those with known renal impairment

Severe Infections

• For more severe infections, higher doses may be needed 2
• If daily doses greater than 4g are required, parenteral cephalosporins should be considered 2

Clinical Pearls

• Cephalexin achieves high urinary concentrations (500-1000 μg/mL) following 250-500 mg oral doses, which exceeds the minimum inhibitory concentration for most urinary pathogens 4
• Cephalexin is classified as an alternative agent rather than first-line therapy for uncomplicated UTIs according to IDSA guidelines 3
• For complicated UTIs or pyelonephritis, treatment duration should be extended to 7-14 days 5, 1

Common Pitfalls to Avoid

1. Inadequate duration: Ensure complete 5-7 day course for uncomplicated UTIs and 7-14 days for complicated UTIs
2. Ignoring local resistance patterns: Consider local resistance before prescribing empirically
3. Failing to obtain cultures: Obtain urine cultures before starting antibiotics, especially in complicated cases
4. Not replacing indwelling catheters: Replace catheters that have been in place ≥2 weeks before initiating antimicrobial therapy 1

Alternative Agents

If cephalexin is not appropriate, consider:

• Nitrofurantoin 100 mg twice daily for 5 days
• Fosfomycin 3 g single dose
• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days
• Fluoroquinolones (reserved for cases where other options cannot be used) 1