Arixtra: Protection Against Post-surgical Blood Clots
In 2002, the Food and Drug Administration (FDA) approved ]]>Arixtra]]> (fondaparinux), a blood thinner to help prevent the dangerous blood clots that can occur after certain types of surgery.
When a blood clot forms in a vein in the legs, it is called ]]>deep vein thrombosis]]> (DVT). DVT can block blood flow through the vein. Symptoms include pain, swelling, warmth, and a change in skin color of the affected leg. However, sometimes there are no symptoms unless a clot breaks loose and travels through the bloodstream to the lungs. This is called ]]>pulmonary embolism]]> , and can be fatal.
People who undergo certain surgeries are at high risk of developing DVT. These include:
As a precautionary measure, these patients are often given blood-thinning drugs after surgery. The most commonly used drugs are ]]>heparin]]> and a group of drugs called low molecular-weight heparins. One example is ]]>Lovenox]]> .
Arixtra is the first synthetic drug created to prevent deep vein thrombosis. It is made from the portion of the heparin molecule that inhibits a key factor in blood clotting—activated Factor X. In studies done by the drug's manufacturer of more than 4000 patients, those given Arixtra were 50% less likely to develop a blood clot than those given Lovenox.
However, in this study, Arixtra was given six hours after surgery, while Lovenox was given 18 hours after surgery. The 18-hour mark is the standard time for administration of Lovenox. The FDA pointed out that if both drugs were given after six hours, they may have worked equally as well. Therefore, the FDA approval does not say that Arixtra is superior to standard therapy, but that it is an effective option.
All blood-thinning drugs can cause excessive, dangerous bleeding, and Arixtra is no exception. During clinical trials, the risk of bleeding was greater for certain groups of people, and therefore this drug should not be given to the following:
- Those with serious kidney failure
- Those who weigh less than 110 pounds
- Age >75 years old is listed by the manufacturer, but is not a contraindication
- Active major bleeding, ]]>bacterial endocarditis]]> , and patients with thrombocytopenia associated with a positive in vitro test for antiplatelet antibody in the presence of fondaparinux sodium are other contraindications listed by the manufacturer
Food and Drug Administration
Your Orthopedic Connection
Bauer, KA, Eriksson, BI, Lassen, MR, et al. Fondaparinux Compared With Enoxaparin for the Prevention of Venous Thromboembolism After Elective Major Knee Surgery. N Engl J Med. 2001; 345:1305.
Eriksson, BI, Bauer, KA, Lassen, MR, et al. Fondaparinux Compared With Enoxaparin for the Prevention of Venous Thromboembolism After Hip-Fracture Surgery. N Engl J Med. 2001; 345:1298.
Last reviewed July 2008 by ]]>Marcin Chwistek, MD]]>
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