From the Guidelines
Augmentin is primarily renally cleared, with both amoxicillin and clavulanic acid being eliminated through renal excretion, as indicated by the dosing recommendations for patients with impaired kidney function in various guidelines, including those for bronchiectasis treatment 1.
The British Thoracic Society guideline for bronchiectasis in adults, published in Thorax in 2019 1, provides recommendations for antimicrobial agents, including amoxicillin with clavulanic acid (Augmentin), but does not directly discuss its renal clearance. However, the fact that dosage adjustments are often necessary for patients with impaired kidney function implies renal clearance.
- Key points to consider:
- Amoxicillin and clavulanic acid, the components of Augmentin, are known to be excreted in the urine, indicating renal clearance.
- Patients with renal impairment may require dose adjustments to prevent accumulation and potential toxicity.
- The mechanism of renal clearance involves both glomerular filtration and tubular secretion.
- Monitoring kidney function is crucial when prescribing Augmentin, especially in high-risk patients such as the elderly or those with pre-existing kidney disease.
Given the importance of renal function in the clearance of Augmentin, it is essential to consider renal clearance when prescribing this medication, particularly in patients with known kidney issues or those at risk of developing kidney problems 1.
From the FDA Drug Label
Approximately 50% to 70% of the amoxicillin and approximately 25% to 40% of the clavulanic acid are excreted unchanged in urine during the first 6 hours after administration of a single amoxicillin and clavulanate potassium tablet, 250 mg/125 mg or 500 mg/125 mg. High blood levels may occur more readily in patients with impaired renal function because of decreased renal clearance of both amoxicillin and clavulanate Key Points:
- Amoxicillin is renally cleared, with 50-70% excreted unchanged in urine.
- Clavulanic acid is also renally cleared, with 25-40% excreted unchanged in urine.
- Renal impairment can lead to decreased renal clearance of both amoxicillin and clavulanate, resulting in high blood levels 2, 2.
From the Research
Renal Clearance of Augmentin
- Augmentin, a combination of amoxicillin and clavulanic acid, is renally cleared, as evidenced by studies showing a decrease in total body clearance and renal clearance of both amoxicillin and clavulanic acid with decreasing renal function 3, 4.
- The decrease in total body clearance is more pronounced for amoxicillin than for clavulanic acid, resulting in an increase in the ratio of amoxicillin to clavulanic acid with decreasing glomerular filtration rate 3.
- Hemodialysis increases the clearance of both amoxicillin and clavulanic acid, with clavulanic acid being influenced to a greater extent due to its higher extraction ratio 5.
- After oral administration, approximately 50% of amoxicillin and 39% of clavulanic acid are renally excreted within 9 hours 6.
- In critically ill children, augmented renal clearance implies a need for increased amoxicillin-clavulanic acid dosing to achieve therapeutic targets 7.
Factors Affecting Renal Clearance
- Renal function, as measured by glomerular filtration rate, significantly affects the pharmacokinetics of amoxicillin and clavulanic acid 3, 4.
- Hemodialysis increases the clearance of both amoxicillin and clavulanic acid, with clavulanic acid being influenced to a greater extent 5.
- Plasma cystatin C and concomitant treatment with vasopressors also influence amoxicillin clearance in critically ill children 7.