💊 Fondaparinux

Fondaparinux is a synthetic selective Factor Xa inhibitor, belonging to the class of antithrombotic agents. It is a pentasaccharide that mimics the antithrombin-binding site of heparin.

Fondaparinux selectively and reversibly binds to antithrombin III, causing a conformational change that greatly enhances antithrombin's ability to inactivate Factor Xa. This leads to the inhibition of thrombin generation and clot formation.

Fondaparinux is indicated for the prophylaxis of venous thromboembolism (VTE) in patients undergoing major orthopaedic surgery (e.g., hip fracture, knee replacement) and abdominal surgery. It is also used for the treatment of acute deep vein thrombosis (DVT) and pulmonary embolism (PE). Fondaparinux can be used in patients with a history of heparin-induced thrombocytopenia (HIT) as it does not bind to platelet factor 4.

Absolute contraindications include active major bleeding, severe renal impairment (creatinine clearance below 30 mL/min), and bacterial endocarditis. It is also contraindicated in patients with a body weight below 50 kg for VTE prophylaxis due to an increased risk of bleeding. Caution is advised in patients with a high risk of bleeding or concurrent use of other agents affecting haemostasis.

The most significant adverse effect is bleeding, which can range from minor injection site haematomas to major haemorrhage. Other common side effects include anaemia, nausea, and fever. Thrombocytopenia is rare and fondaparinux does not cause HIT. Hypersensitivity reactions can occur.

Routine coagulation monitoring (e.g., APTT, INR) is not required with fondaparinux. Renal function should be assessed before initiation and periodically during treatment, as it is primarily renally excreted. Platelet counts are generally not routinely monitored unless there is a clinical indication.

Always check for active bleeding, severe renal impairment, and body weight (for prophylaxis). Counsel patients on the subcutaneous injection technique and to report any signs of bleeding. Be mindful of potential interactions with other medications that increase bleeding risk. It does not have a specific reversal agent, making careful patient selection crucial.

Fondaparinux is a synthetic, selective Factor Xa inhibitor with a long half-life, allowing for once-daily dosing. Its key advantage is its safety in patients with a history of HIT, as it does not cross-react with heparin-dependent antibodies. Remember its contraindication in severe renal impairment and the lack of a specific antidote.

SBAs often highlight fondaparinux as an option for VTE prophylaxis, especially in orthopaedic surgery or in patients with a history of HIT. Questions may focus on its selective Factor Xa inhibition and its safety profile regarding HIT. Recognising the contraindication in severe renal impairment and low body weight is also important.