Fondaparinux

Pronunciation: fon-da-PAIR-in-uks.

Generic name
fondaparinux sodium
Drug class
Anticoagulant (selective factor Xa inhibitor)
Form
Solution for injection, pre-filled syringe (1.5 mg, 2.5 mg, 5 mg, 7.5 mg, 10 mg depending on market and indication)
Route
Subcutaneous injection
Legal status
Prescription-only, hospital/specialist-administered injectable

Availability and supply rules vary by country

Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand

Australia: Arixtra (5) · Full directory

What fondaparinux sodium is and how it works

Fondaparinux is an injectable anticoagulant (blood thinner) that works by blocking a specific clotting factor (factor Xa). It is used to prevent and treat blood clots in the veins (venous thromboembolism), including after certain types of surgery, and in some countries as part of treatment for certain heart attacks. (1)

Fondaparinux carries a genuine, serious risk of bleeding, and a specific boxed-warning risk of a spinal or epidural blood clot if it is given around the time of spinal or epidural anesthesia or a spinal puncture, which can cause long-term or permanent paralysis. It also requires dose selection based on body weight and kidney function, and blood tests to monitor platelet counts. It should only ever be given and monitored by a healthcare professional -- never adjust the dose or timing yourself.

Mechanism of action: how fondaparinux sodium works

Fondaparinux is a synthetic pentasaccharide that selectively binds antithrombin III, potentiating its neutralisation of factor Xa, thereby interrupting the coagulation cascade and inhibiting thrombin formation and clot growth, without directly inactivating thrombin itself. (1)

What fondaparinux sodium is used for

Prevention of blood clots after surgery

Used to prevent deep vein thrombosis (DVT) in adults having hip fracture surgery, hip replacement surgery, knee replacement surgery, or abdominal surgery. (1)

Treatment of deep vein thrombosis and pulmonary embolism

Used, together with warfarin, to treat an acute deep vein thrombosis or acute pulmonary embolism (a blood clot in the lungs) in adults. (1)

Certain heart attacks (acute coronary syndrome)

In some countries, including Australia, used to treat unstable angina or certain types of heart attack (non-ST-elevation and ST-elevation myocardial infarction) in specific clinical situations. (5)

Treatment of venous thromboembolism in children

Used to treat venous thromboembolism in children aged 1 year and older who weigh at least 10 kg, at a weight-based dose with monitoring. (1)

Before taking fondaparinux sodium

Do not take / not appropriate for

  • Do not use fondaparinux if you have severe kidney impairment (creatinine clearance below 30 mL/min). (all countries) (1) (2)
  • Do not use fondaparinux for clot prevention if you weigh less than 50 kg -- this specific use is contraindicated at this body weight. (all countries) (1)
  • Do not use fondaparinux if you have active major bleeding, bacterial endocarditis (a heart valve infection), or a history of a serious allergic reaction to it. (all countries) (1)
  • Do not use fondaparinux if you have thrombocytopenia (a low platelet count) together with a positive blood test for antibodies against platelets in the presence of fondaparinux. (all countries) (1)

Tell your clinician about

  • Any history of bleeding problems, stomach ulcers, or recent surgery.
  • Your kidney function, since dosing and safety depend heavily on it.
  • Your exact body weight, since dosing is weight-based for treatment and there is a hard cut-off for the prevention indication.
  • Any planned spinal or epidural anesthesia, spinal puncture (such as a lumbar puncture), or spinal catheter, and any history of spine problems or spinal surgery.
  • All other medicines that affect bleeding or clotting, including NSAIDs, other blood thinners, and antiplatelet medicines.
  • Whether you are pregnant, planning pregnancy, or breastfeeding.
(1) (2)

How to take fondaparinux sodium

  • Fondaparinux is given as an injection just under the skin (subcutaneously), usually once daily, by or under the direction of a healthcare professional.
  • Your exact dose and timing are individualised based on why you are taking it, your body weight, and your kidney function -- never adjust the dose or timing yourself.
  • If you are scheduled for spinal or epidural anesthesia or a spinal puncture, your care team will plan the timing of your fondaparinux doses carefully around the procedure because of the boxed-warning spinal/epidural blood clot risk.
(1)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)

Missed dose

Contact your care team immediately for guidance if a dose is missed -- do not give an extra dose or change the schedule yourself.

Overdose

Seek urgent medical attention for a suspected overdose. Signs of too much anticoagulant effect include unusual bruising, nosebleeds, blood in urine or stool, or unusually heavy bleeding from a cut or injection site. (1)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Bruising, bleeding, or irritation at the injection site.

What to notice: Bruising, bleeding, or irritation at the injection site.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Low blood count (anemia).

What to notice: Low blood count (anemia).

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Nausea.

What to notice: Nausea.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Serious warnings

Signs of a spinal or epidural blood clot (hematoma) — boxed_warning

Symptoms: New or worsening back pain, numbness, tingling, weakness in the legs, or loss of control of bowel or bladder function, especially after spinal or epidural anesthesia or a spinal puncture.

Action: Seek emergency medical help immediately -- this can indicate a spinal or epidural blood clot pressing on the spinal cord, which can cause long-term or permanent paralysis if not treated urgently. (1)

Signs of serious bleeding — boxed_warning_adjacent_serious

Symptoms: Unusual bruising, nosebleeds that won't stop, blood in urine or stool, coughing up blood, severe headache, or bleeding from the gums.

Action: Contact your clinician or seek emergency care immediately -- fondaparinux increases bleeding risk, and this risk is higher with kidney impairment, low body weight, or other blood-thinning medicines. (1)

Signs of a low platelet count (thrombocytopenia) — high caution

Symptoms: Unusual bruising or small red/purple spots on the skin, unexplained bleeding, or fatigue.

Action: Your platelet count will be monitored during treatment; fondaparinux is stopped if the platelet count falls below 100,000/mm3. Report any unusual bruising or bleeding to your care team promptly. (1)

Signs of a serious allergic reaction — emergency

Symptoms: Swelling of the face, lips, tongue, or throat; difficulty breathing; widespread rash or hives.

Action: Seek emergency medical help immediately. (1)

Interactions

  • Other medicines that affect bleeding or clotting -- including NSAIDs, aspirin and other antiplatelet medicines, warfarin, and other anticoagulants -- increase bleeding risk and increase the spinal/epidural hematoma risk if combined around the time of a spinal procedure. (1) (4)
  • Fondaparinux is given together with warfarin specifically for the DVT/PE treatment indication, under close monitoring, until the target INR is reached. (1)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

Discuss with your clinician; anticoagulant choice in pregnancy requires individualised specialist assessment. (1) (2) (3) (4) (5) (6)

Breastfeeding

Discuss with your clinician before use while breastfeeding. (1) (2) (3) (4) (5) (6)

Children

Approved for treatment of venous thromboembolism in children aged 1 year and older weighing at least 10 kg, at a specific weight-based dose with monitoring; not established for the adult prevention indications. (1) (2) (3) (4) (5) (6)

Elderly

No specific age-based dose change beyond the general weight- and renal-function-based dosing described in this page, but older adults are more likely to have reduced kidney function, which affects both dosing and bleeding risk. (1) (2) (3) (4) (5) (6)

Hepatic_impairment

Not specifically quantified in the sources reviewed for this dossier; use with caution and clinician guidance. (1) (2) (3) (4) (5) (6)

Renal_impairment

Contraindicated in severe renal impairment (creatinine clearance below 30 mL/min); used with caution in moderate renal impairment (creatinine clearance 30-50 mL/min), with increased bleeding risk as kidney function declines, since fondaparinux is cleared by the kidneys. (1) (2) (3) (4) (5) (6)

Source_ids

US-DAILYMED-ARIXTRA-2026,UK-EMC-ARIXTRA-SMPC-2026,CA-HEALTHCANADA-ARIXTRA-PM-2026 (1) (2) (3) (4) (5) (6)

Monitoring

Before starting

  • Kidney function (creatinine clearance)
  • Body weight
  • Baseline platelet count
  • Review of other medicines affecting bleeding/clotting
  • Review of any planned spinal/epidural procedure

During treatment

  • Platelet count monitored during treatment; fondaparinux discontinued if it falls below 100,000/mm3.
  • Kidney function reassessed periodically, since bleeding risk rises as kidney function declines.
  • Close monitoring for neurological signs (back pain, numbness, weakness, bowel/bladder changes) around the time of any spinal or epidural procedure.
(1) (4)

Storage

Store pre-filled syringes as directed on the product label, typically at room temperature, protected from light, out of reach of children.

Study the drug class: Heparins and related parenteral anticoagulants

Professional information

Clinician-facing context only, sourced from the current US FDA prescribing information and UK/Canada regulator sources reviewed for this dossier; verify against the current full label before prescribing.

United States

Indication: VTE prophylaxis (adults)

Dose summary: 2.5 mg subcutaneously once daily, starting 6-8 hours post-surgery, for 5-9 days (up to 24 additional days for hip fracture surgery); contraindicated under 50 kg body weight.

Renal context: Contraindicated in severe renal impairment (CrCl <30 mL/min). (1)

United States

Indication: VTE treatment (adults, with warfarin)

Dose summary: Weight-based once daily: 5 mg (<50 kg), 7.5 mg (50-100 kg), 10 mg (>100 kg), continued until INR 2-3 on warfarin.

Renal context: Contraindicated in severe renal impairment (CrCl <30 mL/min); increased bleeding risk with declining renal function. (1)

Mechanism of action

Hepatic guidance

Not specifically quantified in the sources reviewed for this dossier.

Overdose note

No specific antidote; manage with supportive care and close monitoring for bleeding; protamine sulfate is not considered effective for reversing fondaparinux's anticoagulant effect. (1)

Frequently asked questions

Why does fondaparinux have a boxed warning about spinal procedures?

Because, like other anticoagulants (including low molecular weight heparins), fondaparinux carries a genuine risk that a blood clot can form in or around the spine if it is given around the time of spinal or epidural anesthesia or a spinal puncture. This clot can press on the spinal cord and cause long-term or permanent paralysis, which is why your care team carefully times fondaparinux doses around any such procedure and monitors you closely afterward for warning signs. (1)

Why is fondaparinux dosed by body weight and kidney function?

Because both affect how much fondaparinux stays in your body and how much bleeding risk you have. It is contraindicated below 50 kg body weight for the clot-prevention use, and contraindicated in severe kidney impairment (creatinine clearance under 30 mL/min), since the kidneys clear this medicine and reduced clearance increases bleeding risk. (1)

Why do I need blood tests while taking fondaparinux?

Your platelet count is monitored because fondaparinux can, in rare cases, cause a drop in platelets; treatment is stopped if the count falls below 100,000/mm3. Your kidney function may also be checked periodically, since it affects both dosing and bleeding risk. (1)

What is the mechanism of action of fondaparinux sodium?

Fondaparinux is a synthetic pentasaccharide that selectively binds antithrombin III, potentiating its neutralisation of factor Xa, thereby interrupting the coagulation cascade and inhibiting thrombin formation and clot growth, without directly inactivating thrombin itself. (1)

What is the generic name of Fondaparinux?

The generic name is fondaparinux sodium. (1) (3)

What class of drug is fondaparinux sodium?

Fondaparinux is classed as: Anticoagulant (selective factor Xa inhibitor). (1) (3)

References

  1. ARIXTRA (fondaparinux sodium) injection, solution -- full prescribing informationU.S. Food and Drug Administration / DailyMed (NIH), full prescribing information, Mylan/Aspen · United States · accessed 2026-07-30 · source 1
  2. Arixtra (fondaparinux sodium) solution for injection -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom -- Aspen Pharma Trading Limited · United Kingdom · accessed 2026-07-30 · source 2
  3. Arixtra, INN-fondaparinux sodium -- EPAREuropean Medicines Agency (EMA) -- centralised EU marketing authorisation, EPAR · European Union · accessed 2026-07-30 · source 3
  4. ARIXTRA (fondaparinux sodium) injection -- Product MonographHealth Canada product monograph · Canada · accessed 2026-07-30 · source 4
  5. ARIXTRA fondaparinux sodium solution for injection syringe -- ARTG entries 80279 / 97798 / 97799 / 97800Therapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-30 · source 5
  6. Fondaparinux sodium -- Hospital Medicines List (HML) entry RS1184PHARMAC (Pharmaceutical Management Agency), New Zealand -- Hospital Medicines List (HML) · New Zealand · accessed 2026-07-30 · source 6

Brand names by country

Single-ingredient fondaparinux sodium names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • Arixtra7.5 mg/.6mL, 10 mg/.8mL, 5 mg/.4mL, 2.5 mg/.5mL · mylan institutional llc

United Kingdom

  • Arixtra (2)MHRA licensed emc smpc confirmed · 1.5 mg/0.3 mL, 2.5 mg/0.5 mL, 5 mg/0.4 mL, 7.5 mg/0.6 mL · Aspen Pharma Trading Limited

Canada

  • ARIXTRA

Australia

  • Arixtra (5)TGA ARTG registered 2002-03-25 confirmed · 2.5 mg/0.5 mL, 5.0 mg/0.4 mL, 7.5 mg/0.6 mL, 10.0 mg/0.8 mL · Aspen Pharmacare Australia Pty Ltd

New Zealand

  • Fondaparinux sodium (generic listing) (6)PHARMAC Hospital Medicines List restricted form confirmed · not specified in source · not specified in source
View brands in additional countries.

European Union

Arixtra (3)

This page provides general reference information about fondaparinux and is not a substitute for advice from the clinician managing your treatment. All dosing, timing around spinal/epidural procedures, and monitoring decisions should be made with your prescriber or care team.

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