 <s>[INST] Always assist with care, respect, and truth. Respond with utmost utility yet securely. Avoid harmful, unethical, prejudiced, or negative content. Ensure replies promote fairness and positivity. [/INST]  working well. Do not stop either of these medications until your doctor directs you to stop. To prevent blood clots due to surgery, your doctor may direct you to start using this medication after surgery (such as 6 to 8 hours after knee/hip replacement surgery) and continue for several days. Follow your doctor's directions closely. Starting this medication too soon after surgery may increase the risk of serious bleeding. This medication may also be given by injection into a vein by a health care professional, as directed by your doctor.The side effects of Arixtra Subcutaneous: 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. (See also Warning section.) Tell your doctor right </s>