Selective Factor Xa Inhibitor (Synthetic Pentasaccharide)

Fondaparinux Sodium

Brand names: Arixtra

Fondaparinux is a synthetic factor Xa inhibitor given by subcutaneous injection for venous thromboembolism prophylaxis and treatment and in acute coronary syndromes.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

For subcutaneous use, do not mix with other injections or infusions. ( 2.1 ) Prophylaxis of deep vein thrombosis: Fondaparinux sodium 2.5 mg subcutaneously once daily after hemostasis has been established. The initial dose should be given no earlier than 6 to 8 hours after surgery and continued for 5 to 9 days. For patients undergoing hip fracture surgery, extended prophylaxis up to 24 additional days is recommended. ( 2.2 , 2.3 ) Treatment of deep vein thrombosis and pulmonary embolism: Fondaparinux sodium 5 mg (body weight <50 kg), 7.5 mg (50 to 100 kg), or 10 mg (>100 kg) subcutaneously once daily. Treatment should continue for at least 5 days until INR 2 to 3 achieved with warfarin …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2021-09-10. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Clinical monograph

How it works

It binds antithrombin to selectively inhibit factor Xa; unlike heparins it does not cross-react in heparin-induced thrombocytopenia.

Prescribing in practice

It is renally cleared — avoid in severe renal impairment and reduce/monitor in moderate impairment.
It does not cause heparin-induced thrombocytopenia, so it is an option where that is a concern.
Observe timing around neuraxial procedures.

Monitoring

Monitor renal function; routine coagulation monitoring is not required.

Counselling the patient

It is given as an injection under the skin.
Report unusual bleeding or bruising.

Evidence & guidelines

Used for VTE prophylaxis/treatment and in ACS, and as an option where heparin-induced thrombocytopenia is a concern.

Reference: NICE guidelines; OASIS-5 trial; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways