Skip to content
ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Indirect Factor Xa Inhibitor — VTE Prophylaxis / Treatment Pregnancy: UK SPC §4.6, verbatim — Pregnancy: 'There are no adequate data from the use of fondaparinux in pregnant women. Animal studies are insufficient with respect to effects on pregnancy, embryo/foetal development, parturition and postnatal development because of limited exposure. Fondaparinux should not be prescribed to pregnant women unless clearly necessary.' Breastfeeding: 'Fondaparinux is excreted in rat milk but it is not known whether fondaparinux is excreted in human milk. Breastfeeding is not recommended during treatment with fondaparinux. Oral absorption by the child is however unlikely.' Fertility: 'There are no data available on the effect of fondaparinux on human fertility. Animal studies do not show any effect on fertility.' US label §8.1 for context: 'Available data from published literature and postmarketing reports have not reported a clear association with fondaparinux sodium and adverse developmental outcomes... demonstrated low placental transfer of fondaparinux sodium... There are risks to the mother associated with untreated venous thromboembolism in pregnancy and a risk of haemorrhage in the mother and fetus associated with use of anticoagulants.'

Fondaparinux

Brand names: Arixtra

Fondaparinux is a synthetic parenteral anticoagulant given by subcutaneous injection for prophylaxis and treatment of venous thromboembolism and in the management of acute coronary syndromes.

Adult dose

Dose: VTE PROPHYLAXIS (this page's primary indication) — 2.5 mg once daily by subcutaneous injection. After major orthopaedic or abdominal surgery the initial dose is given 6 hours following surgical closure provided haemostasis has been established, and treatment continues until the risk of venous thrombo-embolism has diminished, usually until the patient is ambulant, at least 5 to 9 days after surgery; after hip fracture surgery prolonged prophylaxis for up to an additional 24 days should be considered. In medical patients at high risk of thromboembolic complications on individual risk assessment the dose is also 2.5 mg once daily, with a treatment duration of 6 to 14 days clinically studied. THE SAME 2.5 mg ONCE-DAILY DOSE is licensed in this SPC for three further indications: unstable angina / NSTEMI (subcutaneous, started as soon as possible after diagnosis, continued for up to a maximum of 8 days or until hospital discharge if earlier); STEMI (first dose intravenous, subsequent doses subcutaneous, same 8-day limit); and superficial-vein thrombosis of the lower limbs (subcutaneous, minimum 30 days and up to a maximum of 45 days in patients at high risk of thromboembolic complications).
Route: Deep subcutaneous injection, patient lying down, alternating between the left and right anterolateral and the left and right posterolateral abdominal wall; do not expel the air bubble from the pre-filled syringe before injecting. Intravenous administration is used for the FIRST DOSE IN STEMI PATIENTS ONLY — §4.2: 'Intravenous administration should be through an existing intravenous line either directly or using a small volume (25 or 50ml) 0.9% saline minibag... If administered via a minibag, the infusion should be given over 1 to 2 minutes.' §4.4: 'Fondaparinux must not be administered intramuscularly.'
Frequency: Once daily
SCOPE — this page's category is 'VTE Prophylaxis / Treatment' and its dose line leads with prophylaxis; the prophylaxis regimen is what is published above, complete and from the UK SPC. THE DVT/PE TREATMENT WEIGHT BANDS THIS PAGE ALSO LISTS (5 mg / 7.5 mg / 10 mg) ARE NOT PUBLISHED FROM THIS BUNDLE: the UK licence fetched is the 2.5 mg prophylaxis syringe and has no treatment regimen, and although the US label in the bundle does have a DVT/PE treatment section, its weight thresholds are CORRUPTED in the fetched text — §2.4 reads 'the recommended dose of fondaparinux sodium injection is 5 mg (body weight 100 kg) by subcutaneous injection once daily', with the comparators lost, and the Highlights line is mangled the same way. No treatment weight band may be reconstructed from that. Fetch the Arixtra 10 mg/0.8 ml treatment SPC (https://www.medicines.org.uk/emc/product/3340/smpc) before publishing treatment doses on this page. PROPHYLAXIS VERBATIM (§4.2): 'Patients undergoing major orthopaedic or abdominal surgery — The recommended dose of fondaparinux is 2.5 mg once daily administered post-operatively by subcutaneous injection. The initial dose should be given 6 hours following surgical closure provided that haemostasis has been established. Treatment should be continued until the risk of venous thrombo-embolism has diminished, usually until the patient is ambulant, at least 5 to 9 days after surgery. Experience shows that in patients undergoing hip fracture surgery, the risk of VTE continues beyond 9 days after surgery. In these patients the use of prolonged prophylaxis with fondaparinux should be considered for up to an additional 24 days.' MEDICAL PATIENTS: 'The recommended dose of fondaparinux is 2.5 mg once daily administered by subcutaneous injection. A treatment duration of 6-14 days has been clinically studied in medical patients.' UA/NSTEMI VERBATIM: 'The recommended dose of fondaparinux is 2.5 mg once daily, administered by subcutaneous injection. Treatment should be initiated as soon as possible following diagnosis and continued for up to a maximum of 8 days or until hospital discharge if that occurs earlier. If a patient is to undergo percutaneous coronary intervention (PCI), unfractionated heparin (UFH) as per standard practice should be administered during PCI... In the pivotal UA/NSTEMI clinical trial, treatment with fondaparinux was restarted no earlier than 2 hours after sheath removal.' STEMI VERBATIM: 'The recommended dose of fondaparinux is 2.5 mg once daily. The first dose of fondaparinux is administered intravenously and subsequent doses are administered by subcutaneous injection... In the pivotal STEMI clinical trial, treatment with fondaparinux was restarted no earlier than 3 hours after sheath removal.' SUPERFICIAL-VEIN THROMBOSIS VERBATIM: 'The recommended dose of fondaparinux is 2.5 mg once daily, administered by subcutaneous injection. Patients eligible for fondaparinux 2.5 mg treatment should have acute, symptomatic, isolated, spontaneous superficial-vein thrombosis of the lower limbs, at least 5 cm long and documented by ultrasonographic investigation or other objective methods. Treatment should be initiated as soon as possible following diagnosis and after exclusion of concomitant DVT or superficial-vein thrombosis within 3 cm from the sapheno-femoral junction. Treatment should be continued for a minimum of 30 days and up to a maximum of 45 days in patients at high risk of thromboembolic complications.' NO MAXIMUM DOSE IS PUBLISHED: the only 'maximum' wordings in this SPC are treatment DURATIONS — 'up to a maximum of 8 days' (UA/NSTEMI and STEMI) and 'up to a maximum of 45 days' (superficial-vein thrombosis) — not dose ceilings, and 2.5 mg once daily is the single recommended dose for every indication in this licence. TIMING IN HIGHER-RISK SURGICAL PATIENTS (§4.2): 'In patients undergoing surgery, timing of the first fondaparinux injection requires strict adherence in patients ≥75 years, and/or with body weight <50 kg and/or with renal impairment with creatinine clearance ranging between 20 to 50 ml/min. The first fondaparinux administration should be given not earlier than 6 hours following surgical closure. The injection should not be given unless haemostasis has been established.' CABG (§4.2): 'In STEMI or UA/NSTEMI patients who are to undergo coronary artery bypass graft (CABG) surgery, fondaparinux where possible, should not be given during the 24 hours before surgery and may be restarted 48 hours post-operatively.' SURGERY DURING SVT TREATMENT: 'fondaparinux, where possible, should not be given during the 24 hours before surgery. Fondaparinux may be restarted at least 6 hours post-operatively provided haemostasis has been achieved.' PCI WARNING (§4.4): 'In STEMI patients undergoing primary PCI, the use of fondaparinux prior to and during PCI is not recommended... In UA/NSTEMI and STEMI patients undergoing non-primary PCI, the use of fondaparinux as the sole anticoagulant during PCI is not recommended due to an increased risk of guiding catheter thrombus. Therefore adjunctive UFH should be used during non-primary PCI according to standard practice.' LOW BODY WEIGHT (§4.2): for prevention of VTE and treatment of UA/NSTEMI and STEMI, 'Patients with body weight <50 kg are at increased risk of bleeding. Elimination of fondaparinux decreases with weight. Fondaparinux should be used with caution in these patients.' For superficial-vein thrombosis, 'The safety and efficacy of fondaparinux in patients with body weight less than 50 kg has not been studied, therefore fondaparinux is not recommended for use in these patients.' UNSUPPORTED PAGE CLAIMS — nothing in this bundle supports the page's statements that fondaparinux does not bind PF4, carries essentially zero HIT risk, is preferred in HIT, cannot be reversed with protamine, or that andexanet alfa may partially reverse it. The US label in the bundle in fact contraindicates fondaparinux in 'Thrombocytopenia associated with a positive in vitro test for anti-platelet antibody in the presence of fondaparinux sodium' and requires discontinuation if the platelet count falls below 100,000/mm3. Re-source or remove those pearls. Some sections of the product information we used were incomplete — check the full SPC.

Paediatric dose

NO PAEDIATRIC DOSE. UK SPC §4.2, verbatim: 'Paediatric population - Fondaparinux is not recommended for use in children below 17 years of age due to a lack of data on safety and efficacy.' US label §8.4: 'Safety and effectiveness of fondaparinux sodium in pediatric patients have not been established. Because risk for bleeding during treatment with fondaparinux sodium is increased in adults who weigh <50 kg, bleeding may be a particular safety concern for use of fondaparinux sodium in the pediatric population.' dosePerKg is null and no weight-based calculation should be offered. If a child or adolescent needs thromboprophylaxis or anticoagulation, verify the agent and the dose against a children's formulary and take specialist advice.

Dose adjustments

Renal

Indication-specific in this SPC — §4.2 verbatim. PROPHYLAXIS OF VTE: 'Fondaparinux should not be used in patients with creatinine clearance <20 ml/min (see section 4.3). The dose should be reduced to 1.5 mg once daily in patients with creatinine clearance in the range of 20 to 50 ml/min (see sections 4.4 and 5.2). No dosage reduction is required for patients with mild renal impairment (creatinine clearance >50 ml/min).' TREATMENT OF UA/NSTEMI AND STEMI: 'Fondaparinux should not be used in patients with creatinine clearance < 20 ml/min (see section 4.3). No dosage reduction is required for patients with creatinine clearance > 20 ml/min.' TREATMENT OF SUPERFICIAL-VEIN THROMBOSIS: 'Fondaparinux should not be used in patients with creatinine clearance <20 ml/min (see section 4.3). The dose should be reduced to 1.5 mg once daily in patients with creatinine clearance in the range of 20 to 50 ml/min... The safety and efficacy of 1.5 mg has not been studied.' The corresponding contraindication in §4.3 of this 2.5 mg licence is 'severe renal impairment defined by creatinine clearance < 20 ml/min'. NOTE the US label instead contraindicates CrCl <30 mL/min, because it covers the treatment strengths as well.

Hepatic

§4.2 verbatim. PREVENTION OF VTE AND TREATMENT OF UA/NSTEMI AND STEMI: 'No dosing adjustment is necessary in patients with either mild or moderate hepatic impairment. In patients with severe hepatic impairment, fondaparinux should be used with care as this patient group has not been studied (see sections 4.4 and 5.2).' TREATMENT OF SUPERFICIAL-VEIN THROMBOSIS: 'The safety and efficacy of fondaparinux in patients with severe hepatic impairment has not been studied, therefore fondaparinux is not recommended for use in these patients (see section 4.4).' US label §2.5 agrees for mild to moderate impairment and adds: 'Patients with hepatic impairment may be particularly vulnerable to bleeding during fondaparinux sodium therapy. Observe these patients closely for signs and symptoms of bleeding.'

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to the active substance or to any of the excipients listed in section 6.1 (UK SPC §4.3)
  • Active clinically significant bleeding (UK SPC §4.3)
  • Acute bacterial endocarditis (UK SPC §4.3)
  • Severe renal impairment defined by creatinine clearance < 20 ml/min (UK SPC §4.3 — this is the threshold of the 2.5 mg PROPHYLAXIS licence fetched here; the treatment-strength licence uses < 30 ml/min, and the US label contraindicates CrCl <30 mL/min because it covers both)
  • US label §4 only: 'Thrombocytopenia associated with a positive in vitro test for anti-platelet antibody in the presence of fondaparinux sodium.'
  • US label §4 only: 'Body weight <50 kg (venous thromboembolism [VTE] prophylaxis only).' The UK SPC does not contraindicate this — for prophylaxis and ACS it advises caution, and for superficial-vein thrombosis it says fondaparinux 'is not recommended for use in these patients'.
  • US label §4 only: 'History of serious hypersensitivity reaction (e.g., angioedema, anaphylactoid/anaphylactic reactions) to fondaparinux sodium.'
  • Not a contraindication but a prohibition (UK SPC §4.4): 'Fondaparinux must not be administered intramuscularly.'

Side effects

  • Bleeding is the principal risk — UK SPC §4.8: 'The most commonly reported serious adverse reactions reported with fondaparinux are bleeding complications (various sites including rare cases of intracranial/ intracerebral and retroperitoneal bleedings) and anaemia.'
  • Common (≥ 1/100, <1/10), blood and lymphatic system: anaemia, post-operative haemorrhage
  • Uncommon (≥ 1/1,000, <1/100), bleeding at other sites: uterovaginal haemorrhage, haemoptysis, haematuria, haematoma, gingival bleeding, purpura, epistaxis, gastrointestinal bleeding, haemarthrosis, ocular bleeding, bruise
  • Uncommon, platelet and coagulation: thrombocytopenia, thrombocythaemia, platelet abnormal, coagulation disorder
  • Rare (≥ 1/10,000, <1/1,000): retroperitoneal bleeding, hepatic bleeding, intracranial/intracerebral bleeding
  • Infections and infestations: post-operative wound infections
  • Immune system: allergic reaction, including very rare reports of angioedema and anaphylactoid/anaphylactic reaction
  • Metabolism: hypokalaemia; non-protein-nitrogen (Npn) increased
  • Nervous system — common: headache; uncommon: anxiety, confusion, dizziness, somnolence, vertigo
  • Vascular: hypotension. Respiratory: dyspnoea (common), coughing (uncommon)
  • Gastrointestinal — common: nausea, vomiting; uncommon: abdominal pain, dyspepsia, gastritis (the table is cut off mid-entry at this point)
  • US label §5.1: 'Spinal or epidural hematomas, which may result in long-term or permanent paralysis, can occur.'
  • The UK §4.8 table is cut off at the source-fetch limit part-way through the gastrointestinal row, so this list is not the complete adverse-reaction table.

Monitoring

  • Platelet count — US label §5.5: 'Thrombocytopenia can occur with the administration of fondaparinux sodium. Thrombocytopenia of any degree should be monitored closely. Discontinue fondaparinux sodium if the platelet count falls below 100,000/mm3.'
  • Renal function before administration and during treatment, particularly in the elderly — US label §8.5: 'Because elderly patients are more likely to have decreased renal function, assess renal function prior to fondaparinux sodium administration.' The UK SPC makes renal function the determinant of both eligibility (<20 ml/min) and dose (1.5 mg at 20–50 ml/min for prophylaxis and superficial-vein thrombosis).
  • Signs and symptoms of bleeding, especially where bleeding risk is increased — UK SPC §4.4: 'Fondaparinux should be used with caution in patients who have an increased risk of haemorrhage, such as those with congenital or acquired bleeding disorders (e.g. platelet count <50,000/mm3), active ulcerative gastrointestinal disease and recent intracranial haemorrhage or shortly after brain, spinal or ophthalmic surgery.'
  • Close monitoring if antiplatelet drugs or NSAIDs must be co-administered — UK SPC §4.4 (prevention of VTE): 'Other antiplatelet medicinal products (acetylsalicylic acid, dipyridamole, sulfinpyrazone, ticlopidine or clopidogrel), and NSAIDs should be used with caution. If co-administration is essential, close monitoring is necessary.'
  • Before starting fondaparinux for superficial-vein thrombosis, confirm the diagnosis objectively — UK SPC §4.4: 'Presence of superficial-vein thrombosis greater than 3 cm from the sapheno-femoral junction should be confirmed and concomitant DVT should be excluded by compression ultrasound or objective methods prior to initiating treatment of fondaparinux.'
  • No routine coagulation or anti-Xa monitoring requirement appears in any fetched section of either label (the page's 'anti-Xa levels not routinely required but available' line is not supported by this bundle).

Clinical monograph

How it works

It is a selective indirect inhibitor of activated factor X (factor Xa), binding antithrombin to potentiate the neutralisation of Xa without inhibiting thrombin directly.

Prescribing in practice

  • Contraindicated and the dose must be reduced or avoided in significant renal impairment because it is renally cleared and accumulates, raising bleeding risk.
  • Carries a risk of haemorrhage and should be used cautiously with other agents affecting haemostasis, including antiplatelets and other anticoagulants.
  • It does not generally cross-react in heparin-induced thrombocytopenia, making it a useful alternative, but neuraxial procedures require caution because of spinal haematoma risk.

Monitoring

Routine coagulation monitoring is not required, but renal function, platelet count and signs of bleeding should be assessed during treatment.

Counselling the patient

  • Report any unusual bruising, bleeding or black stools promptly.
  • It is given as a subcutaneous injection and the technique should be demonstrated for self-administration.

Evidence & guidelines

Established in pivotal trials for VTE prophylaxis and treatment and in acute coronary syndrome management, and recommended in NICE and specialist guidance.

Reference: NICE NG89 (VTE Prevention); MATISSE-DVT/PE Trials; ESC Guidelines 2019 PE; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Pathways