Effects of hemodialysis on the pharmacokinetics of amoxicillin/clavulanic acid combination.

The effects that renal disease and hemodialysis have on the pharmacokinetics of amoxicillin/clavulanic acid combination were studied in a patient receiving this combination for the treatment of a Nocardia asteroides infection. Hemodialysis increased the clearance of both substances as evidenced by lower serum concentrations during the on-dialysis day, i.e., 2.3 +/- 0.8 vs. 5.9 +/- 1.2 micrograms/ml for clavulanic acid and 8.0 +/- 1.8 vs. 12.4 +/- 0.9 micrograms/ml for amoxicillin. Clavulanic acid appeared to be influenced to a greater extent as compared to amoxicillin because of its higher extraction ratio (0.74 vs. 0.44) as well as a higher observed ratio of amoxicillin to clavulanic acid during the on-dialysis day (3.59 +/- 1.27 vs. 2.28 +/- 0.65; p less than 0.05). Comparison of the area under the serum concentration-time (AUC) during the off-dialysis day with published AUC values suggested accumulation of amoxicillin/clavulanic acid. These data indicate that dosage adjustments for amoxicillin/clavulanic acid may be required in patients with chronic renal failure who are on hemodialysis. Further studies in this patient population are needed before specific dosing guidelines can be provided.