fondaparinux sodium: clinical use

Prescribing considerations

• Assess bleeding risk, renal function, age, body weight, liver disease and planned invasive or neuraxial procedures before prescribing
• Confirm eligible superficial-vein thrombosis objectively and exclude concomitant deep-vein thrombosis
• Use caution with a history of heparin-induced thrombocytopenia; cross-reactivity is unusual, but rare cases have been reported
• There is no known specific antidote; significant bleeding requires discontinuation, investigation and supportive haemostatic management

Contraindications and cautions

• Hypersensitivity to fondaparinux or an excipient
• Active clinically significant bleeding
• Acute bacterial endocarditis
• Severe renal impairment, defined for the selected product as creatinine clearance below 20 mL/min

Monitoring

• Monitor clinically for bleeding, bruising and anaemia
• Check renal function before treatment and reassess when it may change
• Consider full blood count and platelet assessment where clinically indicated
• Routine PT, INR and aPTT do not reliably measure its anticoagulant effect; a fondaparinux-calibrated anti-Xa assay may be required in selected specialist situations

Clinical pharmacology

Fondaparinux is completely absorbed after subcutaneous injection, binds selectively to antithrombin and indirectly inhibits factor Xa. It is not substantially metabolised, does not inhibit major CYP450 enzymes and is mainly excreted unchanged in urine; exposure and persistence increase as renal function declines.

Formulation and product differences

• The selected product is a clear, colourless solution in a single-use pre-filled glass syringe with a needle-protection system
• The needle shield contains dry natural latex rubber and may cause reactions in latex-sensitive people
• The formulation is essentially sodium-free and must not be mixed with other medicinal products
• An MHRA caution-in-use notice issued on 28 January 2026 reported very rare brown needle discolouration and blockage affecting unexpired Arixtra batches; inspect syringes and do not use one that appears discoloured, damaged or blocked

Injection

Route: Parenteral

Strengths: 1.5 mg/0.3 mL, 2.5 mg/0.5 mL, 5 mg/0.4 mL, 7.5 mg/0.6 mL, 10 mg/0.8 mL