Fondaparinux blocks the activity of certain clotting substances in the blood.

Fondaparinux is used to prevent a type of blood clot called deep vein thrombosis (DVT), which can lead to blood clots in the lungs (pulmonary embolism). A DVT can occur after certain types of surgery.

Fondaparinux is also used together with warfarin (Coumadin, Jantoven) to treat DVT, including pulmonary embolism.

Fondaparinux may also be used for purposes not listed in this medication guide.

You should not use fondaparinux if you have active bleeding, severe kidney disease, an infection in the lining of your heart, or low platelets in your blood after testing positive for a certain antibody. You should not use fondaparinux after surgery if you weigh less than 110 pounds (50 kilograms).

Fondaparinux can cause you to bleed more easily. Call your doctor at once if you have signs of bleeding such as: bleeding gums, nosebleeds, heavy menstrual periods or abnormal vaginal bleeding, blood in your urine, bloody or tarry stools, coughing up blood or vomit that looks like coffee grounds.

Many other drugs can increase your risk of bleeding when used with fondaparinux. Tell your doctor about all medicines you have recently used.

Fondaparinux can cause a very serious blood clot around your spinal cord if you undergo a spinal tap or receive spinal anesthesia (epidural). Tell any doctor who treats you that you are using fondaparinux.

Fondaparinux is usually given every day until your bleeding condition improves. Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Fondaparinux is injected under the skin. A healthcare provider may teach you how to properly use the medication by yourself.

Read and carefully follow any Instructions for Use provided with your medicine. Do not use fondaparinux if you don't understand all instructions for proper use. Ask your doctor or pharmacist if you have questions.

You should be sitting or lying down during the injection. Do not inject fondaparinux into a muscle or a vein.

Prepare your injection only when you are ready to give it. Do not use if the medicine has changed colors or has particles in it. Call your pharmacist for new medicine.

Your care provider will show you where on your body to inject fondaparinux. Use a different place each time you give an injection. Do not inject into the same place two times in a row.

Fondaparinux can make it easier for you to bleed, even from a minor injury. Seek medical attention if you have bleeding that will not stop.

If you need surgery, dental work, or a medical procedure, tell the doctor or dentist ahead of time that you are using this medication. If you need anesthesia, you may need to stop using fondaparinux for a short time.

While using fondaparinux, your blood and your stool (bowel movement) may need to be tested often. Your nerve and muscle function may also need to be tested.

Store at room temperature away from moisture and heat. Do not freeze.

Use a needle and syringe only once and then place them in a puncture-proof "sharps" container. Follow state or local laws about how to dispose of this container. Keep it out of the reach of children and pets.

You should not use this medicine if you have ever had a severe allergic reaction to fondaparinux, or if you have:

• active or uncontrolled bleeding;

• severe kidney disease;

• an infection in the lining of your heart (also called bacterial endocarditis); or

• a low level of platelets in your blood after testing positive for a certain antibody while using fondaparinux.

You should not use fondaparinux to prevent blood clots after surgery if you weigh less than 110 pounds (50 kilograms).

Fondaparinux can cause a very serious blood clot around your spinal cord if you undergo a spinal tap or receive spinal anesthesia (epidural). This type of blood clot could cause long-term paralysis, and may be more likely to occur if:

• you have a genetic spinal defect;

• you have had a spinal catheter;

• you have a history of spinal surgery or repeated spinal taps;

• you have recently had a spinal tap or epidural anesthesia;

• you are taking an NSAID--Advil, Aleve, Motrin, and others; or

• you are using other medicines to treat or prevent blood clots.

Tell your doctor if you have ever had:

• a bleeding disorder that is inherited or caused by disease;

• a stroke;

• eye problems caused by diabetes;

• uncontrolled high blood pressure;

• stomach or intestinal bleeding or ulcer;

• brain, spine, or eye surgery;

• an allergy to latex; or

• liver or kidney disease.

Using fondaparinux during pregnancy may cause bleeding in the mother or the unborn baby. Tell your doctor if you are pregnant or if you become pregnant.

It may not be safe to breast-feed while using this medicine. Ask your doctor about any risk.

Use the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not use two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. Overdose can cause excessive bleeding.

Avoid activities that may increase your risk of bleeding or injury. Use extra care to prevent bleeding while shaving or brushing your teeth.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Also seek emergency medical attention if you have symptoms of a spinal blood clot: back pain, numbness or muscle weakness in your lower body, or loss of bladder or bowel control.

Fondaparinux can cause you to bleed more easily. Call your doctor at once if you have signs of bleeding such as:

• easy bruising or bleeding (nosebleeds, bleeding gums, heavy menstrual bleeding);

• pain, swelling, or drainage from a wound or where a needle was injected in your skin;

• bleeding from wounds or needle injections, any bleeding that will not stop;

• headaches, dizziness, weakness, feeling like you might pass out;

• urine that looks red, pink, or brown; or

• bloody or tarry stools, coughing up blood or vomit that looks like coffee grounds.

Also call your doctor at once if you have:

• a light-headed feeling, like you might pass out;

• low potassium level--leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling;

• low red blood cells (anemia)--pale skin, unusual tiredness, feeling light-headed or short of breath, cold hands and feet;

• low potassium--leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling;

• low red blood cells (anemia)--pale skin, feeling light-headed or short of breath, rapid heart rate, trouble concentrating; or

Common side effects of fondaparinux may include:

• bleeding, bruising;

• sleep problems (insomnia);

• rash, blisters;

• dizziness, confusion; or

• minor bleeding, rash, itching, or oozing where the medicine was injected.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Tell your doctor about all your other medicines, especially:

• any other medications to treat or prevent blood clots;

• a blood thinner--heparin warfarin (Coumadin, Jantoven); or

• NSAIDs (nonsteroidal anti-inflammatory drugs)--aspirin, ibuprofen (Advil, Motrin), naproxen (Aleve), celecoxib, diclofenac, indomethacin, meloxicam, and others.

This list is not complete and many other drugs may affect fondaparinux. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.