What is the maximum daily dose of Cephalexin (Cefalexin) for a patient with Impaired renal function?

Maximum Daily Dose of Cephalexin in Renal Impairment

For patients with impaired renal function (creatinine clearance <30 mL/min), reduce the cephalexin dose proportionally to the degree of renal dysfunction, with dosing intervals extended up to 20 times longer than normal depending on severity of impairment. 1, 2

Dosing Algorithm Based on Renal Function

Normal Renal Function (CrCl >50 mL/min)

• Standard adult dosing: 250-500 mg every 6 hours (maximum 4 g/day) 1
• Pediatric dosing: 50-100 mg/kg/day divided into 4 doses (maximum 500 mg per dose) 3

Moderate Renal Impairment (CrCl 30-50 mL/min)

• Reduce dose by 50% OR double the dosing interval 1
• Example: 250-500 mg every 12 hours instead of every 6 hours 1

Severe Renal Impairment (CrCl 10-30 mL/min)

• Further dose reduction required: 250 mg every 12-24 hours 1
• Dosing interval may need to be extended up to 20 times normal based on tubular function 2

End-Stage Renal Disease (CrCl <10 mL/min)

• Anephric patients: 250-500 mg results in high, prolonged serum concentrations with peak levels at 1 hour (occasionally delayed to 6-12 hours) 4
• Maximum recommended: 250 mg every 24 hours or less frequently 1

Critical Pharmacokinetic Considerations

Cephalexin depends heavily on active renal tubular secretion for elimination, not just glomerular filtration. 2

• 70-100% of the dose appears unchanged in urine within 6-8 hours in normal renal function 1
• Tubular secretion capacity diminishes substantially in glomerulonephritis and renal failure 2
• Standard creatinine clearance-based adjustments may underestimate required dose reductions 2

Hemodialysis Patients

• Hemodialysis removes 58% of cephalexin over 6 hours 4
• Administer supplemental dose after each dialysis session 4
• Typical post-dialysis dose: 250-500 mg 4

Common Pitfalls to Avoid

Do not rely solely on creatinine clearance for dose adjustment—tubular secretion impairment requires more aggressive interval prolongation than glomerular filtration rate alone would suggest. 2

• Delayed absorption can occur in anephric patients, with peak levels sometimes not appearing until 6-12 hours post-dose rather than the expected 1 hour 4
• Urine concentrations of 500-1000 mcg/mL are achieved after standard doses in normal renal function, far exceeding MIC for common uropathogens, so even reduced doses maintain efficacy for UTI 1
• Children have greater body water turnover and may require higher mg/kg doses than adults despite renal impairment 1

Monitoring Recommendations

• Assess both glomerular filtration (creatinine clearance) and tubular function when determining dosing intervals 2
• Monitor for delayed absorption patterns in severely impaired patients 4
• Adjust dosing based on clinical response and renal function trends 1