What are the appropriate doses of augmentin (amoxicillin + clavulanate) and doxycycline for a patient with a creatinine clearance of 23 mL/min?

Dosing Augmentin and Doxycycline with CrCl 23 mL/min

For a patient with creatinine clearance of 23 mL/min, Augmentin requires dose reduction while doxycycline does not require adjustment.

Augmentin (Amoxicillin-Clavulanate) Dosing

Reduce the dose to 250-500 mg every 12 hours for standard infections, or 500 mg every 12 hours for more severe infections. 1

The FDA label does not provide explicit dosing for CrCl 10-30 mL/min for standard formulations, but extrapolating from available data and the oseltamivir guidance pattern in renal insufficiency 2, 3, the approach is to extend the dosing interval rather than reduce individual doses to maintain adequate peak concentrations.

Key Considerations for Augmentin:

• Amoxicillin component: Approximately 68% renally excreted 4. With CrCl 23 mL/min, the half-life extends from ~1 hour to approximately 7-8 hours 4, 5
• Clavulanic acid component: More hepatically metabolized than amoxicillin, but still significantly affected by renal dysfunction 6
• Both components are dialyzable if the patient requires hemodialysis 6

Practical Dosing Algorithm:

• Standard infections: 250-500 mg PO every 12 hours
• Severe infections: 500 mg PO every 12 hours (maximum)
• Timing: Administer after dialysis if patient is on hemodialysis
• Monitor: Watch for gastrointestinal side effects, particularly C. difficile risk, which is higher with the clavulanic acid component 7

Critical pitfall: Do not use the 875 mg tablet formulation in severe renal impairment—the clavulanic acid dose becomes excessive and increases toxicity risk without additional benefit 7.

Doxycycline Dosing

No dose adjustment is required—use standard dosing of 100 mg PO every 12 hours (or 200 mg loading dose, then 100 mg daily/BID depending on indication). 8

Rationale:

Doxycycline is unique among tetracyclines because renal excretion accounts for only 40% of elimination in normal renal function, and this drops to 1-5% in severe renal insufficiency (CrCl <10 mL/min) 8. The drug compensates through increased fecal/biliary excretion, maintaining a stable half-life of 18-22 hours regardless of renal function 8.

Key Points:

• No accumulation occurs even in severe renal impairment
• Hemodialysis does not alter serum half-life 8
• Standard dosing applies across all levels of renal dysfunction
• No supplemental dosing needed post-dialysis

Common Pitfall to Avoid:

Do not reflexively reduce doxycycline dosing based on creatinine clearance—this is a common error that leads to subtherapeutic levels. Unlike other renally-cleared antibiotics, doxycycline's pharmacokinetics remain stable in renal failure 8.

Summary Algorithm

For CrCl 23 mL/min:

1. Augmentin: Reduce to 250-500 mg every 12 hours (extend interval, maintain dose)
2. Doxycycline: 100 mg every 12 hours (no adjustment needed)
3. If on hemodialysis: Give Augmentin after dialysis; doxycycline timing doesn't matter
4. Monitor: GI tolerance for Augmentin (clavulanic acid side effects), standard monitoring for doxycycline