People using this medication may bleed near the spinal cord after certain spinal procedures. Bleeding in this area can cause paralysis that lasts a long time or could become permanent. Talk with your doctor about the benefits and risks before any spinal procedure. Your doctor may direct you to stop this medication for a certain amount of time before and after the procedure. Carefully follow your doctor's directions. The risk of bleeding may be higher if you have a deformed spine, or have had spinal procedures/surgery before (such as epidural catheter placement, difficult epidural/spinal puncture), or are taking other drugs that can cause bleeding/bruising (including antiplatelet drugs such as clopidogrel, "blood thinners" such as warfarin/rivaroxaban, nonsteroidal anti-inflammatory drugs-NSAIDs such as ibuprofen). Tell your doctor right away if you notice symptoms such as back pain, leg numbness/tingling/weakness, loss of control of the bowels or bladder (incontinence).

Pain, bruising, redness, and swelling at the injection site may occur. Headache, nausea, vomiting, swelling of the hands/feet, or fever may also occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor right away if you have any serious side effects, including: easy bleeding/bruising, dark urine, yellow eyes/skin. This medication may rarely cause serious bleeding. () Tell your doctor right away if you have any signs of serious bleeding, including: shortness of breath, coughing up blood, chest pain, cold/blue fingers or toes, unusual dizziness, fainting, fast/irregular heartbeat, joint/muscle pain, mental/mood changes (such as confusion), numbness/tingling, severe stomach/abdominal pain, bloody/black/tarry stools, red/pinkish urine, vomit that looks like coffee grounds. Get medical help right away if you have any very serious side effects, including: headache that is severe or doesn't go away, vision problems, weakness on one side of the body, trouble speaking, seizures, difficulty moving. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Some products that may interact with this drug include: mifepristone, other drugs that can cause bleeding/bruising (including antiplatelet drugs such as clopidogrel, NSAIDs such as ketorolac, "blood thinners" such as rivaroxaban). Check all prescription and nonprescription medicine labels carefully since many medications contain pain relievers/fever reducers (NSAIDs such as ibuprofen, naproxen, aspirin) which can increase the risk of bleeding when used with fondaparinux. However, if your doctor has told you to take low-dose aspirin to prevent heart attack or stroke (usually 81-162 milligrams a day), you should keep taking the aspirin unless your doctor tells you not to. Ask your doctor or pharmacist for more details.