What is the recommended dosage adjustment for Augmentin (amoxicillin/clavulanate) in a patient with impaired renal function?

Dosage Adjustment for Augmentin in Renal Impairment

For a patient with an eGFR of 41 mL/min, Augmentin (amoxicillin/clavulanate) should be administered at a standard dose but with an extended dosing interval of every 12 hours instead of every 8 hours.

Assessment of Renal Function

The patient's renal parameters indicate moderate renal impairment:

• eGFR: 41 mL/min
• BUN: 31 mg/dL
• Creatinine: 1.3 mg/dL

This corresponds to Stage 3b chronic kidney disease (CKD), which requires dosage adjustment for many medications, including Augmentin.

Pharmacokinetics in Renal Impairment

• Amoxicillin is primarily eliminated via the kidneys (60-70% urinary recovery in normal renal function) 1
• Clavulanic acid also has significant renal elimination
• In patients with renal impairment, the half-life of both components increases:
  • Amoxicillin half-life correlates strongly with creatinine clearance (r = 0.967) 1
  • For patients with moderate renal impairment, drug clearance is reduced, leading to drug accumulation if standard dosing is used

Specific Dosing Recommendations

For a patient with eGFR of 41 mL/min:

• Standard strength Augmentin (500/125 mg):

  • Normal dosing: 500/125 mg every 8 hours
  • Adjusted dosing: 500/125 mg every 12 hours

• High strength Augmentin (875/125 mg):

  • Normal dosing: 875/125 mg every 12 hours
  • Adjusted dosing: 875/125 mg every 12 hours (no change in interval, but monitor closely)

• For severe infections: Consider using standard dose but monitor renal function and clinical response closely

Monitoring Recommendations

1. Monitor renal function regularly during therapy
2. Watch for signs of amoxicillin toxicity:
   • Crystalluria
   • Seizures (rare)
   • Skin rash
3. Monitor for clinical efficacy - if inadequate response, consider alternative antibiotics with less renal dependence

Clinical Considerations

• Extending the dosing interval rather than reducing the dose helps maintain peak concentrations needed for antimicrobial efficacy
• For patients with more severe renal impairment (eGFR <30 mL/min), more significant dosage adjustments would be required
• Hemodialysis removes both amoxicillin and clavulanic acid significantly, with reported dialysis clearances of 77.1 mL/min and 92.8 mL/min respectively 2

Alternative Options

If the patient's infection is severe or the organism has borderline susceptibility to Augmentin, consider:

• Using alternative antibiotics with less renal elimination
• Consulting with infectious disease specialists for personalized dosing strategies
• Therapeutic drug monitoring if available

Remember that appropriate dosing is essential to balance antimicrobial efficacy with the risk of adverse effects in patients with renal impairment.