What is the recommended dosing of Keflex (Cephalexin) for a patient with Chronic Kidney Disease (CKD) and impaired renal function?

Keflex (Cephalexin) Dosing in Chronic Kidney Disease

Cephalexin dosing should be adjusted based on creatinine clearance in patients with chronic kidney disease, with standard dosing for those with CrCl >50 mL/min and reduced dosing for those with more severe renal impairment.

Dosing Recommendations Based on Renal Function

• Normal renal function (CrCl >50 mL/min): Standard dosing of 250-500 mg every 6 hours 1
• Moderate renal impairment (CrCl 30-50 mL/min): No dosage adjustment needed 2
• Severe renal impairment (CrCl 10-30 mL/min): Reduce dose to 250-500 mg every 8-12 hours 2
• End-stage renal disease (CrCl <10 mL/min): Reduce dose to 250-500 mg every 12-24 hours 2
• Hemodialysis patients: Administer dose after dialysis session 2

Monitoring Recommendations

• Baseline assessment: Obtain serum creatinine and calculate creatinine clearance before initiating therapy 1
• Follow-up monitoring: Careful clinical observation and laboratory studies should be performed in patients with markedly impaired renal function 1
• Signs of toxicity: Monitor for neurological symptoms (confusion, hallucinations) which may indicate drug accumulation 2

Pharmacokinetic Considerations

• Cephalexin is primarily eliminated by the kidneys, with 70-100% of the dose excreted unchanged in urine within 6-8 hours 2
• Patients with creatinine clearance less than 30 mL/min require a reduction in cephalexin dosage proportional to the reduced renal function 2
• Cephalexin depends on both glomerular filtration and active tubular secretion for elimination 3

Special Considerations

• Traditional dosing adjustments based solely on creatinine clearance may be inadequate for patients with significant tubular dysfunction 3
• Some research suggests that patients with severe renal impairment may require dosing intervals up to 20 times longer than those with normal renal function 3
• Elderly patients often have decreased renal function even with normal serum creatinine levels due to age-related decline in muscle mass 4

Clinical Pearls and Pitfalls

• Common pitfall: Relying solely on serum creatinine rather than calculated creatinine clearance can lead to overdosing in elderly patients or those with low muscle mass 4
• Monitoring: Regular assessment of renal function during therapy is recommended, especially in elderly patients whose renal function may change during treatment 4
• Drug interactions: Probenecid inhibits the renal excretion of cephalexin and may increase blood levels 1
• Safety: Cephalexin has a relatively wide therapeutic index, making it safer than many other antibiotics in patients with renal impairment 2

Practical Application

• For a patient with CKD and CrCl of 25 mL/min, an appropriate cephalexin regimen would be 500 mg every 8-12 hours 2
• For a patient on hemodialysis, administer the dose after the dialysis session to avoid removing the drug during dialysis 2
• In patients with fluctuating renal function, more frequent monitoring of renal parameters is warranted 4