Evaluation of Factor Xa-Specific Chromogenic Substrate Assays and the Determination of Pharmacokinetics of Fondaparinux

Abstract

Fondaparinux (FPX), a synthesized factor Xa inhibitor, is one of the most popular anticoagulants for the prevention of postoperative venous thromboembolism (VTE). Although routine monitoring is not required, the bleeding adverse events cannot be neglected, and the measurement of anti-Xa activity is expected to be monitored. The primary purpose of this study is to evaluate the performances of 2 chromogenic assays for the detection of anti-Xa activity. Furthermore, the pharmacokinetics of FPX was examined using chromogenic assays. Anti-Xa activity was measured using 2 FPX-based chromogenic substrates (S2222 and STA-Liquid Anti-Xa). The reproducibility, detection limits, linearity, and correlations between the substrates were examined using normal plasma doped with low and high concentrations of FPX formulation. In addition, anti-Xa activity in 235 clinical samples from 164 cases treated was measured, and the pharmacokinetics of FPX was evaluated. Both of the tested substrates were capable of accurately measuring the anti-Xa activity of FPX, with a lower limit of 0.05 μg/mL and a coefficient of variation of less than 10%. The repeated administration of FPX induced a gradual but significant increase in the anti-Xa activity, which was negatively correlated with body weight and estimated glomerular filtration rate. No significant correlation between the anti-Xa activity and the occurrence of postoperative VTE or bleeding event was observed. Anti-Xa activity can be successfully determined using 2 chromogenic assays and automated biochemical analyzers. The clinical significance of anti-Xa activity monitoring should be examined in the future study.

Antithrombotic therapy and body mass: an expert position paper of the ESC Working Group on Thrombosis

“…The anti-Xa activity of 2.5mg inversely correlates with BW between 40 and 100kg. 197 In patients with VTE weighing <50kg, the 2.5mg fixed dose should be used cautiously 195 and is contraindicated by the FDA. 198 On the other hand, a small study on morbidly-obese patients showed an anti-Xa activity below target in ≈50% of patients.…”

Postoperative Anaemia Is a Risk Factor for Bleeding-Related Event in Thromboprophylaxis Using Fondaparinux Sodium Injection after Total Knee or Hip Arthroplasty

“…On the other hand, it has been reported that elevated anti-Xa activity by FPX was observed in patients with renal impairment but not in patients with body weight <50 kg or age >75 years. 27) However, no significant correlation between anti-Xa activity and the occurrence of postoperative bleeding was observed following thromboprophylaxis with FPX. 28) Therefore, together with the results of this study, bleeding following thromboprophylaxis after TKA or THA might not be related to the renal clearance of FPX.…”

“…27) However, no significant correlation between anti-Xa activity and the occurrence of postoperative bleeding was observed following thromboprophylaxis with FPX. 28) Therefore, together with the results of this study, bleeding following thromboprophylaxis after TKA or THA might not be related to the renal clearance of FPX. To determine whether an association exists between anti-Xa activity and bleeding events in patients with thromboprophylaxis with FPX, further investigations are necessary.…”

Facile chemoenzymatic synthesis of unmodified anticoagulant ultra-low molecular weight heparin

“…The in vitro anti-FXa activity was determined using a commercial BIOPHEN™ kit (HYPHEN BioMed, France) based on a previously described two-stage chromogenic substrate method. 31 In short, the synthetic unmodified heparin heptasaccharide 20 and Arixtra were dissolved in 50 mM Tris buffer solution ( pH 7.4) containing 150 mM NaCl and 1% (w/v) BSA in different concentrations, respectively. Factor Xa (FXa), antithrombin (AT) and the chromogenic substrate S-2765 were carefully prepared according to the manufacturer's instruction before the assay.…”