Pharmacokinetics of Certoparin During In Vitro and In Vivo Dialysis

Abstract

The efficacy and safety of certoparin in the prophylaxis of clotting during hemodialysis have recently been proven. Different to other low-molecular weight heparins (LMWHs), certoparin does not accumulate in maintenance dialysis patients for unknown reasons. The purpose of the present study was to examine the impact of the dialysis procedure on the removal of certoparin. In a subgroup of the MEMBRANE study consisting of 12 patients, the pharmacokinetics of certoparin during hemodialysis was determined by means of the anti-Xa activity. In addition, the elimination of certoparin into continuously collected dialysate was assessed. Further, in vitro experiments with human blood-simulating high-flux hemodialysis and hemofiltration were performed to quantify the elimination and the sieving coefficients SK of the two LMWHs certoparin and enoxaparin compared with unfractionated heparin (UFH). The surrogate marker middle molecules inulin and myoglobin served as reference solutes during the experiments. Finally, the adsorption of (125) iodine-radiolabeled certoparin onto the synthetic dialysis membrane was quantified. The clinical study reconfirmed the absence of bioaccumulation of certoparin with anti-Xa activities between <0.01 and 0.02 IU/mL after 24 h. A short plasma half-life time of 2.0 ± 0.7 h was determined during hemodialysis. Of the total certoparin dose injected intravenously prior to hemodialysis, only 2.7% was eliminated into dialysate. The in vitro experiments further revealed only 6% of certoparin to be adsorbed onto the dialysis membrane. The anti-Xa activities of certoparin and enoxaparin slowly declined during in vitro hemofiltration to 87.3 ± 5.5 and 82.5 ± 9.4% of baseline, respectively, while inulin and myoglobin concentrations rapidly decreased. The anti-Xa activity of UFH remained unchanged. The SK of both LMWH and UFH was very low in hemofiltration and particularly in hemodialysis with values ≤0.1. The elimination kinetics during hemodialysis suggests strong protein-binding of certoparin. Different from LMWH significantly cleared by the kidneys, the relatively short half-life time of certoparin of only 2 h during hemodialysis allows a more reliable control of the anti-coagulatory effects and decreases the risk of bleeding complications. Dialytic removal does not significantly contribute to the clearance of certoparin in maintenance dialysis patients.

Keywords: Bioaccumulation; End-stage renal disease; Hemodialysis; Hemofiltration; Low-molecular weight heparin; Unfractionated heparin.