Because antithrombin inhibits thrombin and factors Xa, IXa, and XIa, deficiency of antithrombin predisposes to venous thrombosis.

Antithrombin is a protein that inhibits thrombin and factors Xa, IXa, and XIa. Heterozygous deficiency of plasma antithrombin has a prevalence of about 0.2 to 0.4%; about half of people affected develop venous thromboses. Homozygous deficiency is probably lethal to the fetus in utero. Acquired deficiencies occur in patients with DIC, liver disease, or nephrotic syndrome and during heparinSome Trade Names
HEPFLUSH-10
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or l-asparaginaseSome Trade Names
ELSPAR

therapy. (The inhibitory activity of antithrombin is greatly augmented by heparinSome Trade Names
HEPFLUSH-10
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.)

Laboratory testing involves quantification of plasma inhibition of thrombin in the presence of heparinSome Trade Names
HEPFLUSH-10
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.

Oral warfarinSome Trade Names
COUMADIN
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is used for prophylaxis against venous thromboembolism.

Last full review/revision January 2013 by Joel L. Moake, MD

Content last modified January 2013