Population pharmacokinetics-pharmacodynamics of fondaparinux in dialysis-dependent chronic kidney disease patients undergoing chronic renal replacement therapy.

PURPOSE: Data on the anti-Xa efficacy of fondaparinux in dialysis-dependent chronic kidney disease (DD-CKD) patients are scarce. This study characterizes the pharmacokinetics (PK) and pharmacodynamics (PD) of fondaparinux in DD-CKD patients undergoing renal replacement therapy (RRT), to assess dosing strategies. METHODS: A retrospective, observational study was conducted using data on anti-Xa activity (112 samples) from 12 (3 male and 9 female) DD-CKD patients (median (IQR) age 71 years (63-88), weight 73 kg (59-98.5)). Eleven patients underwent high-flux or low-flux hemodialysis (HD) and one patient underwent peritoneal dialysis. Three patients were also treated with therapeutic plasma exchange (TPE). A non-linear mixed effects analysis was performed using NONMEM 7.3.0. RESULTS: The lab-specific slope of the relationship between fondaparinux concentration and anti-Xa levels was 1.18 IU/µg. In a one-compartment model, clearance (CL) and volume of distribution (Vd) were 0.05289 L/h and 5.55 L, respectively. High-flux HD was found to increase the CL of fondaparinux 2.26 times. TPE also considerably increased CL, but the fold-change could not be accurately estimated. Low-flux HD and peritoneal dialysis did not impact PK parameters. CONCLUSIONS: Model-based simulations showed that standard dosing (2.5 mg three times weekly before HD) results in a median anti-Xa activity of 0.55 IU/mL and 0.98 IU/mL, pre- and post-low-flux HD, respectively. In patients undergoing high-flux HD, these values are approximately 27% lower. Additional caution is warranted with TPE, as this treatment can reduce anti-Xa activity even further.

The clinical use of Fondaparinux: A synthetic heparin pentasaccharide.

Fondaparinux is a synthetic heparin pentasaccharide with a sequence identical to that found in anticoagulant heparin. It is a pure compound with a molecular weight of 1728Da. Fondaparinux catalyzes the conformational change of a serpin or serine protease inhibitor antithrombin III to accelerate the suicidal inactivation of factor Xa over 340-fold, which in turn inhibits thrombin generation in the coagulating signal transduction pathway. Fondaparinux does not inhibit thrombin activity, release tissue factor pathway inhibitor, or possess other properties of heparin such as anti-inflammatory, anti-viral, anti-angiogenesis, anti-neoplastic, and anti-metastatic effects though high affinity interactions with a variety of proteases, protease inhibitors, chemokines, cytokines, growth factors, and their respective receptors. Low antithrombin III levels in blood circulation also affects the efficacy of Fondaparinux. Thus, Fondaparinux represents a refined use of the anti-factor Xa property of heparin. As an anti-factor Xa drug, Fondaparinux has complete bioavailability subcutaneously, instant onset of action, a half-life of 15-20h, and a direct renal excretion without any metabolism. Fondaparinux has been shown to be superior to low molecular weight heparin in preventing deep vein thrombosis. Clinically, Fondaparinux is used for the prevention of deep vein thrombosis in patients who have had orthopedic surgery as well as for the treatment of deep vein thrombosis and pulmonary embolism with limitations of use in elderly, low weight, renal impaired patients and in those receiving spinal anesthesia. Clinical studies showed that Fondaparinux acts in prevention and treatment of venous thromboembolism and in ischemic heart disease without significant risk of bleeding.

Clinical effects with inhibition of multiple coagulative pathways in patients admitted for acute coronary syndrome.

Platelets and the coagulation cascade play key roles in initiation, amplification, and perpetuation of acute coronary syndromes (ACS). In the past few years, there has been great progress in ACS antithrombotic treatment with the introduction of novel anticoagulants (fondaparinux and bivalirudin), more potent P2Y12 inhibitors (prasugrel and ticagrelor) and protease-activated receptor antagonists (vorapaxar). Nonetheless, patients with ACS frequently have recurrent ischemic events despite the use of currently recommended dual antiplatelet therapy, revascularization procedures as appropriate, and other evidence-based secondary preventive measures. This is the rationale beyond intensification of antiplatelet therapy. However, the major downside of intensive antithrombotic therapy is bleeding. When treating ACS patients, clinicians should find the adequate balance between the reduction of thrombotic events by effective drug treatment and the induction of bleeding that is linked to the use of potent or multiple antithrombotic agents. Numerous antithrombotic cocktails including oral anticoagulants with or without aspirin have been tested in large clinical trials with the goal of further reduction of ischemia and bleeding risk. The aim of this review is to discuss clinical outcomes resulting from inhibition of multiple coagulative pathways in patients with ACS in light of evidence from large randomized controlled clinical trials.