Arixtra (Fondaparinux) - Subcutaneous


There is a risk of developing epidural or spinal hematomas when Arixtra (fondaparinux) is used in people undergoing epidural/spinal anesthesia or spinal puncture. These hematomas can cause long-term or permanent paralysis. Indwelling epidural catheter use, concomitant use of drugs affecting homeostasis (e.g., nonsteroidal anti-inflammatory drugs), and traumatic or repeated epidural or spinal puncture can increase this risk.

What Is Arixtra?

Arixtra (fondaparinux) is a prescription anticoagulant used to prevent and treat blood clots in the legs (deep vein thrombosis, or DVT) or lungs (pulmonary embolism, or PE).

Arixtra is an antithrombotic agent in a drug class called selective factor Xa inhibitors. It selectively binds to a protein called antithrombin III to inhibit the activity of factor Xa (an enzyme that helps the body form blood clots). Inhibiting this enzyme interrupts blood coagulation.

It is approved for adults as a subcutaneous (under the skin) injection. A healthcare provider can inject it for you, or you can learn how to inject it for yourself.

Drug Facts

Generic Name: Fondaparinux

Brand Name(s): Arixtra

Drug Availability: Prescription

Administration Route: Subcutaneous

Therapeutic Classification: Anticoagulant

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Fondaparinux

Dosage Form(s): Solution for injection

What Is Arixtra Used For?

Blood clots in the veins of the legs or arms can travel to the lungs, which may lead to impaired breathing, lung damage, and death. Specific surgical procedures increase the risk of these blood clots.

Arixtra is approved to:

A DVT is a blood clot in a deep vein of the body, usually in the arms or legs. Often, a DVT doesn’t cause symptoms, but it can cause swelling or discomfort in the affected area. A DVT can travel to the lungs, causing a PE. However, PE can be the first sign of a DVT for some people. Symptoms of a PE can include shortness of breath, chest pain, or loss of consciousness. This is a dangerous condition that requires urgent medical attention.

How to Take Arixtra

This medication should be injected with a syringe into a skin fold of the lower abdominal area. Arixtra should not be injected into the muscle. 

Your healthcare provider may inject it for you or teach you how to inject it yourself. Usually, a healthcare provider or nurse will give this injection to you. 

What to expect when receiving Arixta treatment will depend on its use.

  • For preventing blood clots after surgery: You would start your first dose between six to eight hours after surgery and continue to use this medication once a day for five to nine days, as directed by your healthcare provider. If you have surgery for a hip fracture, you will be instructed to continue taking Arixtra for up to 24 days.
  • For treatment of DVT or PE: You would receive this treatment, along with warfarin, for at least five days until your internalized normalized ratio (INR) value is between two to three. INR is measured with a blood test. The test measures how much time it takes your blood to clot.

The manufacturer provides instructions for self-injection, but you should also have your healthcare provider show you how to do this:

  • Before injecting the medication, wash your hands with soap and water.
  • Find a spot on your lower abdomen at least 2 inches below your belly button for the injection (alternate between your right and left side daily).
  • Sit down or lie down. 
  • Use an alcohol swab to clean your skin and wait a few seconds for it to dry. 
  • Remove the needle guard by twisting it and pulling it away from the syringe. 
  • Gently pinch the injection area with one hand. 
  • With your other hand, insert the entire length of the needle down at an angle of 90 degrees) into the pinched skin. 
  • Inject all the medicine in the syringe by pressing down on the plunger as far as it goes. 
  • Release the plunger. The needle will withdraw automatically from the skin and pull back into the security sleeve, where it will be locked. 
  • Throw away the used syringe.

Put your used needles and syringes in a proper disposal container immediately after use. Do not throw away needles and syringes with regular trash. Follow your community guidelines for the right way to dispose of your disposal container.


You should store this medication in its original container at a standard room temperature of 68 F to 77 F. You can briefly take it in temperatures as low as 59 F and as high as 86 F.

Off-Label Uses

Healthcare providers may prescribe fondaparinux for off-label uses, meaning for conditions not specifically indicated by the Food and Drug Administration (FDA).

This medication has been used for treating and preventing blood clots in several different conditions:

  • Preventing heart attack or stroke after heart surgery 
  • Treatment of a heart attack 
  • Treatment of heparin-induced thrombocytopenia (although thrombocytopenia is also listed as a potential side effect of Arixtra) 
  • Preventing blood clots in people who have COVID -19 infection and are at risk of blood clots 

When used off-label, the dose and duration of Arixtra may be different than the recommended dose for the approved indications.

How Long Does Arixtra Take to Work?

Arixtra reaches peak concentration in the body about three hours after the dose is administered.

What Are the Side Effects of Arixtra?

You can have mild side effects from taking Arixtra, but sometimes the effects can be severe, requiring medical treatment.

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at or 800-FDA-1088.

Common Side Effects

The most common side effects include:

  • Bleeding, such as prolonged bleeding from a cut 
  • Bruising, potentially from a mild bump or without known trauma 
  • An allergic reaction to the packaging for people who are allergic to latex

Be sure to inform your healthcare provider if you have any side effects.

Severe Side Effects

While taking Arixtra, you can have severe bleeding problems that could be dangerous for your health.

Call your healthcare provider immediately if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Gastrointestinal bleeding, which can cause dark or bloody stools 
  • Prolonged and severe bleeding, which can lead to blood loss 
  • Spinal hematoma (bleeding near the spinal cord) may cause numbness or weakness 
  • Epidural hematoma (bleeding near the brain) can cause a severe headache, weakness, vision loss, seizures, or loss of consciousness 
  • Thrombocytopenia (low blood cells) can cause dizziness, fatigue, loss of consciousness

Get medical attention immediately if you experience any signs of these complications.

Long-Term Side Effects

The effects of this medication should wear off within a few days. However, bleeding complications can have lasting health effects. For example, a spinal or epidural hematoma can cause long-term or permanent paralysis.

Report Side Effects

Arixtra may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Arixtra Should I Take? 

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For injection dosage form:
    • For prevention of deep vein thrombosis following abdominal or stomach surgery:
      • Adults—2.5 milligrams (mg) injected under the skin once a day for 5 to 9 days. The first dose is given 6 to 8 hours after surgery.
      • Children—Use and dose must be determined by your doctor.
    • For prevention of deep vein thrombosis following hip fracture surgery, or hip or knee replacement surgery:
      • Adults—2.5 milligrams (mg) injected under the skin once a day for 5 to 9 days. The first dose is given 6 to 8 hours after surgery.
      • Children—Use and dose must be determined by your doctor.
    • For treatment of deep vein thrombosis and pulmonary embolism:
      • Adults—Dose is based on body weight and must be determined by your doctor. The dose is usually 5 to 10 milligrams (mg) injected under the skin once a day for at least 5 days.
      • Children—Use and dose must be determined by your doctor.

Missed Dose

If you are having the medication injected by a healthcare provider as an outpatient, do not miss your appointments. If you miss one, contact your healthcare provider's office as soon as possible to reschedule.

If you are injecting yourself, do not double up on doses to make up for a missed dose. If you miss an injection, take your dose as soon as you remember.

Overdose: What Happens If I Take Too Much Arixtra?

Taking too much Arixtra can cause severe bleeding complications. Contact a healthcare provider immediately if you take more than prescribed. Likewise, seek medical attention if you have signs of bleeding complications. Sometimes, hemodialysis is used after an overdose, and any symptoms you develop need to be treated. 

What Happens If I Overdose on Arixtra?

If you think you or someone else may have overdosed on Arixtra, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Arixtra, call 911 immediately.


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It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly. Blood tests will be needed to check for unwanted effects. Be sure to keep all appointments.

Fondaparinux may cause bleeding problems. This risk is higher if you have a catheter in your back for pain medicine or anesthesia (sometimes called an "epidural"), or if you have kidney problems. The risk of bleeding increases if your kidney problems get worse. Check with your doctor right away if you have any unusual bleeding or bruising, black, tarry stools, bleeding gums, blood in the urine or stools, tingling, numbness, or weakness of the lower legs, or pinpoint red spots on your skin.

You may bleed or bruise more easily while you are using this medicine. Stay away from rough sports or other situations where you could be bruised, cut, or injured. Be careful when using sharp objects, including razors and fingernail clippers. Avoid nose picking and forceful nose blowing.

Be careful when using a regular toothbrush, dental floss, or toothpick. Your medical doctor, dentist, or nurse may recommend other ways to clean your teeth and gums. Check with your medical doctor before having any dental work done.

Make sure any doctor or dentist who treats you knows that you are using this medicine. You may need to stop using fondaparinux several days before having surgery or medical tests.

Also, tell your doctor if you have received fondaparinux or heparin before and had a reaction called thrombocytopenia (low platelet count in the blood), or if new blood clots formed while you were receiving the medicine.

This medicine may increase your risk of having spinal or epidural blood clots when it is used together with certain other medicines or procedures. Check with your doctor right away if you have midline back pain, numbness, tingling, or weakness in the legs or feet, or loss of control of the bowel or bladder (incontinence).

The needle guard of the prefilled syringe of this medicine contains dry natural latex rubber. Tell your doctor if you have any allergies with latex or rubber.

Check with your doctor before you start or stop taking any other medicine, or change the amount you are taking. This includes prescription or nonprescription (over-the-counter [OTC]) medicines, and herbal or vitamin supplements. Many medicines change the way this medicine affects your body.

What Are Reasons I Shouldn’t Take Arixtra?

Arixtra should not be used if any of the following apply to you:

  • Severe kidney disease (creatinine clearance of <30 milliliters per minute) in the prevention or treatment of venous thromboembolism
  • Active major bleeding
  • Bacterial endocarditis (infection of the heart)
  • Thromboctyopenia with a positive lab test for anti-platelet antibody in the presence of fondaparinux
  • Weight of less than 50 kilograms (110 pounds) when used for prevention of venous thromboembolism
  • Previous allergic reaction to fondaparinux

What Other Medications Interact With Arixtra?

Arixtra can interact with other medications that cause bleeding, leading to an increased risk of bleeding complications.

Unless directed by your healthcare provider, do not use Arixtra with:

This is not a complete list of drug interactions that can occur with Arixtra. Share your prescription and over-the-counter (OTC) medication, vitamin, and herbal supplement use with your healthcare provider to ensure you can safely take Arixtra.

What Medications Are Similar?

Arixtra is considered an antithrombotic agent. Antithrombotics are medications that prevent blood clots. They include anticoagulants that inhibit enzymes in the blood clotting pathway and antiplatelet agents, which prevent platelets from sticking together.

Similar to Arixtra, the following drugs are also factor Xa inhibitors:

  • Xarelto (rivaroxaban)
  • Eliquis (apixaban)
  • Edoxaban

Frequently Asked Questions

  • What is Arixtra used for?

    Arixtra is used to prevent deep venous blood clots (DVT) after certain types of surgery and treat DVT or pulmonary embolism (PE), a blood clot in the lung.

  • How does Arixtra work?

    This medication prevents blood clotting by inhibiting factor Xa, which is part of the body's blood clotting process.

  • What drugs should not be taken with Arixtra?

    This medication should not be taken with nonsteroidal anti-inflammatory drugs (NSAIDs) or other antithrombotic agents (blood thinners) unless your healthcare provider directs you to do so.

  • How long does it take for Arixtra to work?

    This medication may begin to have effects within hours after taking a dose.

  • What are the side effects of Arixtra?

    The most common side effect of Arixtra is excessive bleeding, ranging from mild bruising to severe, life-threatening bleeding in the brain. Let your healthcare provider know if you experience any signs of abnormal bleeding. This can also mean bleeding excessively from a small cut or bruising without noticeable injury.

  • How do I safely stop taking Arixtra?

    Talk to your healthcare provider before stopping Arixtra due to the possible risk of blood clots. They might measure your INR or reevaluate your DVT or PE before deciding to stop this medication. Let them know if you are having any intolerable side effects.

How Can I Stay Healthy While Taking Arixtra?

While taking Arixtra, there are several precautions to consider. Follow these tips for staying healthy while using this medication:

  • Do not participate in activities with a high risk of injury, such as contact sports or activities that have a high risk of falling.
  • Do not miss injection appointments at your healthcare provider's office.
  • If you are giving yourself the injections, learn to inject your medication properly and do not skip doses.
  • Watch for the signs and symptoms of DVT and PE and promptly tell your healthcare provider if symptoms worsen. 
  • Get medical attention immediately if you experience serious side effects of Arixtra. 
  • If you are recovering from surgery, be attentive to your wound care as directed.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. PubChem. Fondaparinux.

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  4. De Luca L, Uguccioni M, Natale E, et al. Effectiveness of fondaparinux vs unfractionated heparin following percutaneous coronary intervention in survivors of out-of-hospital cardiac arrest due to acute myocardial infarction. Eur J Clin Pharmacol. 2021;77:563–1567. doi:10.1007/s00228-021-03152-7

  5. Nilius H, Kaufmann J, Cuker A, Nagler M. Comparative effectiveness and safety of anticoagulants for the treatment of heparin-induced thrombocytopenia. Am J Hematol. 2021;96(7):805-815. doi:10.1002/ajh.26194

  6. Cardillo G, Viggiano GV, Russo V, et al. Antithrombotic and anti-inflammatory effects of eondaparinux and enoxaparin in hospitalized COVID-19 patients: the FONDENOXAVID study. J Blood Med. 2021;12:69-75. doi:10.2147/JBM.S285214

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By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.