Fondaparinux treats and prevents blood clots. Tell your doctor right away if you notice signs of excessive bleeding.

Fondaparinux Overview

Reviewed: August 29, 2012

Fondaparinux is a prescription medication used to treat and prevent blood clots. Fondaparinux, a "blood thinner", belongs to a group of drugs called factor Xa (ten A) inhibitor anticoagulants. These medications work by decreasing the ability of blood to form clots.

Fondaparinux comes in an injectable form and is given by injection under the skin once daily.  

Common side effects include skin reactions, dizziness, and bleeding. 

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  • Other
  • Postoperative Complications
  • Thromboembolism
  • Venous Thrombosis

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Fondaparinux Cautionary Labels


Uses of Fondaparinux

Fondaparinux is a prescription medicine that “thins your blood” (also known as an anticoagulant). Fondaparinux is used to:

  • help prevent blood clots from forming in patients who have had certain surgeries of the hip, knee, or the stomach area (abdominal surgery)
  • treat people who have blood clots in their legs or blood clots that travel to their lungs

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Fondaparinux Brand Names

Fondaparinux may be found in some form under the following brand names:

Fondaparinux Drug Class

Fondaparinux is part of the drug class:

Side Effects of Fondaparinux

Fondaparinux can cause serious side effects. See “Drug Precautions”.

  • Severe bleeding. Certain conditions can increase your risk for severe bleeding, including:
    • some bleeding problems
    • some gastrointestinal problems including ulcers
    • some types of strokes
    • uncontrolled high blood pressure
    • diabetic eye disease
    • spinal surgery
  • Certain kidney problems can also increase your risk of bleeding with fondaparinux. Your doctor may check your kidney function while you are taking fondaparinux.
  • People undergoing surgery who weigh less than 110 pounds should not use fondaparinux.
  • Low blood platelets. Low blood platelets can happen when you take fondaparinux. Platelets are blood cells that help your blood to clot normally. Your doctor may check your platelet counts while you take fondaparinux. You may bruise or bleed more easily while taking fondaparinux, and it may take longer than usual for bleeding to stop.
  • Tell your doctor if you have any of these signs or symptoms of bleeding while taking fondaparinux:
  • any bleeding
  • bruising
  • rash of dark red spots under the skin
  • Allergic reactions. If you experience swelling of the face or mouth or have difficulty in swallowing or breathing, contact your doctor right away. You should stop fondaparinux if this happens.

Other side effects include:

  • Injection site reactions. Bleeding, rash, and itching can happen at the place where you inject fondaparinux.
  • Low red blood cell counts (anemia). Your doctor may check your red blood cell counts while you are taking fondaparinux.
  • Increased liver enzyme test results. Your doctor may check your liver function while you are taking fondaparinux.
  • Sleep problems (insomnia).

These are not all the possible side effects of fondaparinux. Call your doctor if you have any side effects that bother you or don’t go away.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Fondaparinux Interactions

Tell your doctor about all the medicines you take including prescriptions and non-prescription medicines, vitamins, and herbal supplements. Some medicines can increase your risk of bleeding. Especially tell your doctor if you take:

  • aspirin
  • NSAIDS (such as ibuprofen or naproxen)
  • other blood thinner medicines, such as clopidogrel or warfarin

This is not a complete list of fondaparinux drug interactions. Ask your doctor or pharmacist for more information.

Fondaparinux Precautions

Certain medical procedures involving the spine, such as an epidural (pain medication given through the spine), spinal anesthesia, or spinal puncture, may be used during your hospital stay. If you need any of these procedures while receiving fondaparinux, heparins, heparinoids, or low-molecular weight heparins (anticoagulants), you may be at risk for having a blood clot (hematoma) in or around your spine. This type of clot is very serious, as it can cause long-term and possibly permanent paralysis (loss of the ability to move).

If you receive fondaparinux after an epidural or spinal anesthetic is used, as the anesthesia for your surgery, your doctor will watch you closely for problems with feeling (sensation) and being able to move. Tell your doctor right away if you have any of these signs and symptoms, especially in your legs and feet:

  • tingling
  • numbness
  • muscle weakness

Because the risk of bleeding may be higher, tell your doctor before taking fondaparinux if you:

  • are also taking certain other medicines that affect blood clotting such as aspirin, an NSAID (for example, ibuprofen or naproxen), clopidogrel, or warfarin sodium
  • have bleeding problems
  • had problems in the past with pain medication given through the spine
  • have had surgery to your spine
  • have a spinal deformity

Do not take fondaparinux if you have:

  • certain kidney problems
  • active bleeding problems
  • an infection of the heart
  • low platelet counts and if you test positive for a certain antibody while you are taking fondaparinux
  • have a history of a serious hypersensitivity/allergic reaction to fondaparinux or to any of its ingredients

People who weigh less than 110 pounds (50 kg) should not use fondaparinux to prevent blood clots from forming after surgery.

Inform MD

Tell your doctor about all of your medical conditions, including if you:

  • have had any bleeding problems (such as stomach ulcers)
  • have had a stroke
  • have had recent surgeries, including eye surgery
  • have diabetic eye disease
  • have kidney problems
  • have uncontrolled high blood pressure
  • have a latex allergy
  • are pregnant or breastfeeding

Tell your doctor about all the medicines you take including prescriptions and non-prescription medicines, vitamins, and herbal supplements.

Fondaparinux and Pregnancy

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Fondaparinux falls into category B. There are no well-done studies that have been done in humans with fondaparinux. But in animal studies, pregnant animals were given this medication, and the babies did not show any medical issues related to this medication.


Fondaparinux and Lactation

It is not known if fondaparinux crosses into human milk. Because many medications can cross into human milk and because of the possibility for serious adverse reactions in nursing infants with use of this medication, a choice should be made whether to stop nursing or stop the use of this medication. Your doctor and you will decide if the benefits outweigh the risk of using fondaparinux.


Fondaparinux Usage

  • Take fondaparinux exactly as prescribed by your doctor.
  • Fondaparinux is given by injection under the skin (subcutaneous injection). 
  • If your doctor tells you that you may give yourself injections of fondaparinux at home, you will be shown how to give the injections first before you do them on your own.
  • Tell your doctor if you have any bleeding or bruising while taking fondaparinux.
  • If you miss a dose of fondaparinux, take your dose as soon as you remember. Do not take 2 doses at the same time.
  • If you take too much fondaparinux, call your doctor right away.
  • Do not use fondaparinux if:
    • the solution appears discolored (the solution should normally appear clear),
    • you see any particles in the solution, or
    • the syringe is damaged.

How to give an injection of fondaparinux:

Fondaparinux is injected into a skin fold of the lower stomach area (abdomen). Do not inject fondaparinux into muscle. Usually a doctor or nurse will give this injection to you. In some cases you may be taught how to do this yourself. Be sure that you read, understand, and follow the step-by-step instructions in this leaflet, on how to give yourself an injection of fondaparinux.

1. Wash your hands thoroughly with soap and water. Towel dry.

2. Sit or lie down in a comfortable position. Choose a spot on the lower stomach area (abdomen), at least 2 inches below your belly button. Change (alternate) between using the left and right side of the lower abdomen for each injection. If you have any questions talk to your nurse or doctor.

3. Clean the injection area with an alcohol swab.

4. Remove the needle guard, by first twisting it and then pulling it in a straight line away from the body of the syringe. Discard the needle guard. To prevent infection, do not touch the needle or let it come in contact with any surface before the injection. A small air bubble in the syringe is normal. To be sure that you do not lose any medicine from the syringe, do not try to remove air bubbles from the syringe before giving the injection.

5. Gently pinch the skin that has been cleaned to make a fold. Hold the fold between the thumb and the forefinger of one hand during the entire injection.

6. Hold the syringe firmly in your other hand using the finger grip. Insert the full length of the needle directly up and down (at an angle of 90°) into the skin fold.

7. Inject all of the medicine in the syringe by pressing down on the plunger as far as it goes. This will activate the automatic needle protection system.

8. Release the plunger. The needle will withdraw automatically from the skin, and pull back (retract) into the security sleeve where it will be locked.

Follow the instructions given to you by your nurse or doctor about the right way to throw away used syringes and needles. There may be state laws about the right way to dispose of used syringes, needles, and disposal containers.

Fondaparinux Dosage

The recommended daily fondaparinux dose ranges from 2.5 mg to 10 mg. Your doctor will determine the best dosage for you based on the medical condition being treated as well as several other factors. 


Fondaparinux Overdose

If you take too much fondaparinux, call your doctor or local Poison Control Center right away.

Other Requirements

  • Store fondaparinux at room temperature 59°F to 86°F (15°C to 30°C). Do not freeze.
  • Safely, throw away fondaparinux that is out of date or no longer needed.
  • Keep fondaparinux and all medicines out of the reach of children.

Fondaparinux FDA Warning


Epidural or spinal hematomas may occur in patients who are anticoagulated with low molecular weight heparins (LMWH), heparinoids, or fondaparinux sodium and are receiving neuraxial anesthesia or undergoing spinal puncture. These hematomas may result in long-term or permanent paralysis. Consider these risks when scheduling patients for spinal procedures. Factors that can increase the risk of developing epidural or spinal hematomas in these patients include:

  • use of indwelling epidural catheters
  • concomitant use of other drugs that affect hemostasis, such as non-steroidal anti-inflammatory drugs (NSAIDs), platelet inhibitors, or other anticoagulants
  • a history of traumatic or repeated epidural or spinal puncture
  • a history of spinal deformity or spinal surgery

Monitor patients frequently for signs and symptoms of neurologic impairment. If neurologic compromise is noted, urgent treatment is necessary.

Consider the benefit and risks before neuraxial intervention in patients anticoagulated or to be anticoagulated for thromboprophylaxis.