Keflex (Cephalexin) Dosing for eGFR of 35 mL/min/1.73m²
For a patient with an eGFR of 35 mL/min/1.73m², Keflex (cephalexin) should be dosed at 50-100% of the normal dose (250-500 mg) every 8-12 hours, depending on infection severity.
Understanding Renal Dosing for Cephalexin
Cephalexin is primarily eliminated by the kidneys, making dose adjustment necessary in patients with impaired renal function. An eGFR of 35 mL/min/1.73m² falls into the moderate renal impairment category (CKD Stage 3b).
Dosing Algorithm for Cephalexin in Renal Impairment:
For eGFR 30-50 mL/min/1.73m²:
- Standard dose: 250-500 mg
- Frequency: Every 8-12 hours (instead of every 6 hours)
For eGFR 10-30 mL/min/1.73m²:
- Standard dose: 250-500 mg
- Frequency: Every 12-24 hours
For eGFR <10 mL/min/1.73m²:
- Standard dose: 250-500 mg
- Frequency: Every 24-48 hours
Clinical Considerations
Infection Severity
- For mild-moderate infections: 250 mg every 12 hours
- For severe infections: 500 mg every 8-12 hours
Monitoring
- Monitor renal function regularly during therapy
- Watch for signs of drug accumulation (neurotoxicity, seizures)
- Assess clinical response to ensure efficacy at reduced dosing
Important Caveats
Drug Accumulation Risk: Cephalexin can accumulate in renal impairment, potentially leading to neurotoxicity if not properly dose-adjusted 1.
Therapeutic Drug Monitoring: Although not routinely performed for cephalexin, clinical monitoring for efficacy and toxicity is essential.
Avoid Common Pitfalls:
- Using serum creatinine alone rather than eGFR for dosing decisions can lead to overdosing in elderly patients with decreased muscle mass 2.
- Failing to reassess renal function during treatment, especially if the patient's condition changes.
- Not accounting for drug interactions that may further impair renal function.
Special Populations:
By following these guidelines, you can optimize cephalexin therapy for patients with moderate renal impairment while minimizing the risk of adverse effects and maintaining efficacy.