What is the recommended dose reduction for co-amoxiclav (amoxicillin/clavulanic acid) in patients with impaired renal function?

Co-amoxiclav Renal Dose Adjustment

For patients with severe renal impairment (GFR <30 mL/min), co-amoxiclav requires significant dose reduction: use 500/125 mg or 250/125 mg every 12 hours for GFR 10-30 mL/min, and every 24 hours for GFR <10 mL/min, with an additional dose after hemodialysis. 1

Dosing Algorithm by Renal Function

Normal to Mild Impairment (GFR >30 mL/min)

• No dose adjustment required - use standard dosing regimens 2, 1
• Standard adult dosing: 500/125 mg every 12 hours or 250/125 mg every 8 hours 1
• For severe infections or respiratory tract infections: 875/125 mg every 12 hours or 500/125 mg every 8 hours 1

Moderate Impairment (GFR 10-30 mL/min)

• Reduce dosing frequency to every 12 hours 1
• Use 500/125 mg or 250/125 mg every 12 hours depending on infection severity 1
• This represents approximately 50% dose reduction or doubled dosing interval 2
• Critical contraindication: Do NOT use the 875/125 mg formulation in patients with GFR <30 mL/min 1

Severe Impairment (GFR <10 mL/min)

• Reduce dosing frequency to every 24 hours 1
• Use 500/125 mg or 250/125 mg every 24 hours based on infection severity 1
• This represents a 25-50% dose reduction from normal 2

Hemodialysis Patients

• Administer 500/125 mg or 250/125 mg every 24 hours depending on infection severity 1
• Give an additional dose both during and at the end of dialysis 1
• Post-dialysis dosing is crucial to ensure adequate drug exposure and avoid premature drug removal 2
• Administering before dialysis wastes medication and leaves patients undertreated 2

Critical Formulation Considerations

Important dosing caveat: Two 250/125 mg tablets are NOT equivalent to one 500/125 mg tablet because both contain the same amount of clavulanic acid (125 mg) 1. This means:

• Doubling the 250 mg formulation gives excess clavulanic acid
• Always use the appropriate strength tablet rather than substituting multiples of lower strengths 1

Monitoring Considerations

• Hepatically impaired patients require cautious dosing with regular hepatic function monitoring 1
• Renal function should be estimated using creatinine clearance (CrCl), typically via the Cockcroft-Gault formula 3
• The pharmacokinetics of amoxicillin show a linear relationship between elimination rate and creatinine clearance, supporting these dose adjustments 4

Common Pitfalls to Avoid

• Do not assume all antibiotics require identical renal dose adjustments - individualized adjustments based on specific drug properties are necessary 2
• Avoid using 875/125 mg formulation in any patient with GFR <30 mL/min - this is explicitly contraindicated 1
• Do not administer doses before hemodialysis - this removes the drug prematurely and results in subtherapeutic levels 2
• Consider that acute kidney injury (AKI) may resolve within 48 hours in many patients, though co-amoxiclav has a wide therapeutic index making conservative dosing reasonable 5