Augmentin Dosing in Hemodialysis Patients with Fistula-Site Abscess
For a patient on thrice-weekly hemodialysis with a fistula-site abscess, Augmentin 500 mg/125 mg should be administered once every 24 hours (not twice daily), with an additional dose given both during and at the end of each dialysis session.
FDA-Approved Dosing Algorithm for Hemodialysis
The FDA label for amoxicillin/clavulanate provides explicit guidance for hemodialysis patients 1:
- Hemodialysis patients should receive 500 mg/125 mg or 250 mg/125 mg every 24 hours, depending on severity of the infection 1
- They should receive an additional dose both during and at the end of dialysis 1
- For a fistula-site abscess (a more severe soft tissue infection), the 500 mg/125 mg dose is appropriate 1
Why NOT Twice Daily (BID)?
The critical principle in hemodialysis dosing is to extend the dosing interval, not reduce the individual dose. This approach prevents subtherapeutic peak concentrations while avoiding drug accumulation 2:
- Both amoxicillin and clavulanic acid are significantly removed by hemodialysis, with fractional drug removal of approximately 64-65% during a 4-hour dialysis session 3
- Amoxicillin has a terminal half-life of 13.6 hours in hemodialysis patients on non-dialysis days, but only 2.3 hours during dialysis 3
- Clavulanic acid has a terminal half-life of 3.05 hours on non-dialysis days and 1.19 hours during dialysis 3
Practical Dosing Schedule for Thrice-Weekly Hemodialysis
On dialysis days (e.g., Monday, Wednesday, Friday):
- Give 500 mg/125 mg at the start of dialysis 1
- Give an additional 500 mg/125 mg at the end of dialysis 1
On non-dialysis days (e.g., Tuesday, Thursday, Saturday, Sunday):
- Give 500 mg/125 mg once daily 1
Why This Regimen Works
The pharmacokinetic data demonstrate differential clearance between amoxicillin and clavulanic acid in renal failure 4:
- Total body clearance decreases more for amoxicillin than clavulanic acid as GFR declines 4
- The ratio of amoxicillin to clavulanic acid exposure increases dramatically in hemodialysis patients (14.7 ± 5.3) compared to normal renal function (4.9 ± 1.2) 4
- This dosing strategy prevents amoxicillin accumulation while maintaining adequate clavulanic acid concentrations 4
Common Pitfall to Avoid
Do not give 500 mg BID in hemodialysis patients. This would lead to:
- Excessive drug accumulation on non-dialysis days (when clearance is only 14.4 mL/min for amoxicillin) 3
- Potential toxicity from supratherapeutic levels 3
- The FDA explicitly contraindicates standard dosing intervals in severe renal impairment 1
Clinical Efficacy in Dialysis Patients
Augmentin has demonstrated 100% bacteriological success at 24 hours post-therapy in urinary tract infections caused by amoxicillin-resistant organisms, with minimal side effects 5. For a fistula-site abscess, the post-dialysis supplementation ensures adequate tissue penetration throughout the interdialytic period 3.