Virinux

Indications

• Prevention of venous thromboembolism in patients undergoing surgery
• Treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE)
• Alternative anticoagulant in patients with a history of heparin-induced thrombocytopenia (HIT)

Dosage

Adults: The recommended dose for the prevention of venous thromboembolism is 2.5 mg subcutaneously once daily. For the treatment of DVT or PE, the recommended dose is 5 mg, 7.5 mg, or 10 mg subcutaneously once daily depending

Mechanism of action

Fondaparinux exerts its antithrombotic effect by selectively binding to antithrombin III, enhancing its ability to inhibit Factor Xa approximately 300-fold. This inhibition interrupts the coagulation cascade, leading to decreased thrombin formation and thrombus development. Unlike heparin, fondaparinux is less likely to induce HIT, although rare cases have been reported.

Pharmacodynamics

Fondaparinux binds specifically to ATIII, enhancing its neutralizing action on Factor Xa, which decreases the conversion of prothrombin to thrombin, thereby reducing fibrin formation. This disruption of the coagulation cascade leads to a decrease in blood clot formation, while fondaparinux does not inactivate thrombin and has no significant effect on platelet function or fibrinolytic activity at therapeutic doses.

Pharmacokinetics

Fondaparinux has a predictable pharmacokinetic profile with a bioavailability of nearly 100% after subcutaneous administration. It has a half-life of approximately 17 hours, allowing for once-daily dosing. Fondaparinux is primarily eliminated through renal excretion, necessitating caution in patients with renal impairment. Monitoring of anticoagulant activity is not typically required, but anti-factor Xa assays can be used in special populations.

Contra-indications

• Active bleeding
• Severe renal impairment (creatinine clearance <30 mL/min)
• Hypersensitivity to fondaparinux or any of its excipients
• Bacterial endocarditis
• History of heparin-induced thrombocytopenia (HIT) with antibodies

Adverse effects

• Bleeding complications
• Anemia
• Thrombocytopenia
• Injection site reactions
• Nausea
• Vomiting

Interactions

• Increased risk of bleeding with concomitant use of other anticoagulants
• NSAIDs may increase the risk of bleeding
• Antiplatelet agents may enhance bleeding risk
• Caution when used with drugs that affect hemostasis

Precautions

• Use with caution in patients with renal impairment
• Monitor for signs of bleeding during therapy
• Assess the risk of thrombocytopenia
• Consider alternative anticoagulation strategies in patients with a history of HIT

Pregnancy

Fondaparinux should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Limited data are available on its use in pregnancy.

Breast-feeding

Fondaparinux is excreted in human milk, but its effect on the nursing infant is unknown. Caution is advised when administering to breastfeeding women.

Storage

Store at 2 to 8 degrees Celsius. Do not freeze. Keep the pre-filled syringes in the original carton to protect from light.

Formulations

• Subcutaneous injection solution (single-use pre-filled syringes)

Indications

• Prophylaxis of venous thromboembolism (VTE) in patients undergoing major orthopedic surgery of the hip or leg
• Prophylaxis of VTE in medical patients immobilized due to acute illness
• Treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE)
• As part of dual therapy with an antiplatelet agent in patients with stable coronary, cerebrovascular or peripheral arterial disease

Dosage

Adults: 2.5 mg once daily by subcutaneous injection. For treatment of superficial vein thrombosis, the same dosage applies for adults weighing 50 kg and above for at least 30 days, with a maximum of 45 days if there is a high risk of thromboembolic complications. Treatment should be stopped 24 hours before surgery and restarted at least 6 hours postoperatively

Mechanism of action

Fondaparinux sodium binds to antithrombin III, resulting in a conformational change that accelerates the inhibition of factor Xa. This inhibition prevents the conversion of prothrombin to thrombin, ultimately reducing fibrin formation and thrombus development.

Pharmacodynamics

The pharmacodynamic effects of fondaparinux sodium include dose-dependent anticoagulation with a predictable pharmacological response. It does not require routine coagulation monitoring, such as INR tests, unlike other anticoagulants. The onset of action is rapid, with peak anticoagulant effects observed within 2 to 3 hours after subcutaneous administration.

Pharmacokinetics

Fondaparinux sodium has a bioavailability of nearly 100% when administered subcutaneously. It exhibits a volume of distribution of approximately 7 liters and is primarily eliminated via renal excretion. The half-life ranges from 17 to 21 hours in healthy individuals, allowing for once-daily dosing. The drug is not significantly metabolized by the liver, which reduces the potential for drug-drug interactions.

Contra-indications

• Severe uncontrolled hypertension
• Active bleeding or bleeding diathesis
• Concurrent use with any other anticoagulant, except when switching therapy
• Recent non-trivial spontaneous bleeding
• Significant bleeding risk due to surgery or trauma

Adverse effects

• Abdominal pain
• Dizziness
• Nausea
• Headache
• Skin reactions
• Anemia
• CNS hemorrhage
• Thrombocytopenia

Interactions

• Concomitant use with other anticoagulants
• Edoxaban should not be used as an alternative to unfractionated heparin in certain patients

Precautions

• Discontinue treatment at least 24 hours before a surgical procedure
• Caution in elderly patients and those with a high risk of bleeding
• Monitor for signs of bleeding complications

Pregnancy

Manufacturer advises avoidance due to potential toxicity in animal studies.

Breast-feeding

Manufacturer advises avoidance as the drug is present in milk in animal studies.

Storage

Store at room temperature, protect from light and moisture.

Formulations

• Fondaparinux sodium 2.5 mg solution for injection

Mechanism of action

The antithrombotic activity of fondaparinux is the result of ATIII-mediated selective inhibition of Factor Xa. By selectively binding to ATIII, Fondaparinux potentiates (about 300 times) the neutralization of Factor Xa by ATIII. Neutralization of Factor Xa interrupts the blood coagulation cascade and thus inhibits thrombin formation and thrombus development. It is thought that fondaparinux is unlikely to induce thrombocytopenia via a heparin-induced thrombocytopenia (HIT)-like mechanism given its chemical structure. As a result, fondaparinux has been used as an alternative anticoagulant in heparin-induced thrombocytopenia (HIT) patients. However, it is important to note that rare cases of HIT have been reported in patients treated with fondaparinux. Antithrombin III generally neutralizes coagulation factor Xa, thrombin, and other coagulation factors, but these reactions are slow in the absence of heparin or fondaparinux. Fondaparinux accelerates the rate at which antithrombin neutralizes factor Xa by inducing a conformational change in antithrombin. This conformational change increases the affinity of antithrombin III for factor Xa, a key enzyme in the coagulation cascade. With fondaparinux therapy, anticoagulation appears to result from rapid inhibition of factor Xa by antithrombin III (about 300-fold greater than innate activity), which inhibits the conversion of prothrombin to thrombin and subsequent thrombus formation. Unlike heparin, which interacts with many plasma components, fondaparinux binds selectively to antithrombin III. Because of its small molecular size, fondaparinux cannot bind simultaneously to antithrombin III and thrombin and therefore is unable to inactivate thrombin itself. At the recommended dosage, fondaparinux does not affect fibrinolytic activity and cannot lyse established thrombi. Fondaparinux generally does not affect platelet function or global clotting function tests (eg, prothrombin time [PT], bleeding time, activated partial thromboplastin time [aPTT]) when administered at the recommended dosage. The antithrombotic activity of fondaparinux sodium is the result of antithrombin III (ATIII)-mediated selective inhibition of Factor Xa. By selectively binding to ATIII, fondaparinux sodium potentiates (about 300 times) the innate neutralization of Factor Xa by ATIII. Neutralization of Factor Xa interrupts the blood coagulation cascade and thus inhibits thrombin formation and thrombus development. Fondaparinux sodium does not inactivate thrombin (activated Factor II) and has no known effect on platelet function. At the recommended dose, fondaparinux sodium does not affect fibrinolytic activity or bleeding time. The limitations of conventional anticoagulants have stimulated the development of new anticoagulants. The central position of factor Xa (FXa) at the junction of the intrinsic and extrinsic pathways in the coagulation cascade means that direct and indirect FXa inhibitors have increasingly changed antithrombotic strategies. FXa inhibitors potently and selectively inhibit thrombin formation rather than thrombin activity. Direct FXa inhibitors may directly bind to FXa, whereas indirect inhibitors are dependent on antithrombin. Direct inhibitors may bind free FXa and, in contrast to indirect inhibitors, FXa within the prothrombinase complex or within clots as well. Fondaparinux is the prototype indirect FXa inhibitor and has been extensively studied in the prevention and treatment of thromboembolic diseases, including acute coronary syndromes. ... Fondaparinux is a selective inhibitor of activated factor X. Its structure is the copy of the heparin pentasaccharide sequence, the shortest chain required for antithrombin inhibition of activated factor X without antithrombin action. Fondaparinux has no effect on coagulation tests and does not bind to platelet factor 4 or promote heparin-induced thrombocytopenia. Fondaparinux inhibits thrombin generation and the growth of thrombi in in vitro and in vivo mo

Pharmacodynamics

Fondaparinux binds specifically to the natural anticoagulant factor, ATIII. Binding to ATIII potentiates the neutralizing action of ATIII on Factor Xa 300-times. Neutralization of Factor Xa decreases the conversion of prothrombin to thrombin, which subsequently decreases the conversion of fibrinogen to fibrin (loose meshwork). The decrease in thrombin also decreases the activation of Factor XIII, which decreases the conversion of fibrin in its loose meshwork form to its stabilized meshwork form. Disruption of the coagulation cascade effectively decreases the formation of blood clots. Fondaparinux does not inactivate thrombin (activated Factor II). According to the manufacturer, fondaparinux has no known effect on platelet function. In studies comparing fondaparinux to enoxaparin, decreases in platelet levels were observed in similar numbers of patients from both groups (2-5%). At the recommended dose, Fondaparinux does not affect fibrinolytic activity or bleeding time. There is no antidote for fondaparinux. Monitoring of the anticoagulant activity of fondaparinux is not generally required. The anti-factor Xa assay may be used to monitor therapy in special populations such as those with renal impairment or who are pregnant. Complete blood count (CBC) and kidney function should be monitored during treatment.