Antithrombin III

1. Health Canada Product Monograph — Antithrombin III

• Antithrombin III is used to prevent and treat abnormal blood clotting in people with an inherited deficiency of antithrombin III, including during surgery, pregnancy, and delivery.

• Antithrombin III has not been evaluated in controlled trials in pregnancy, but published clinical experience supports its use, and because pregnancy itself raises clotting risk it is generally given to pregnant women with antithrombin III deficiency when clearly needed.

• Antithrombin III has not been formally studied in breastfeeding women, so it should be used during breastfeeding only if clearly needed.

• There is no specific information on the use of antithrombin III in older adults; dosing is individualized based on antithrombin activity level and clinical response regardless of age.

• Antithrombin III has not been established as safe and effective in children through controlled clinical trials, so it should be used in children only under close specialist supervision.

• Antithrombin III is generally well tolerated; reported reactions have included dizziness, tremor, and a sensation of warmth or flushing.

Serious side effects require immediate discussion with the prescriber or emergency care.

• Antithrombin III can rarely cause allergic or anaphylactic-type reactions, including fever, hives, nausea, and difficulty breathing, and because it is made from pooled human plasma there is a small residual risk of transmitting infectious agents such as viruses.

• Antithrombin III should be used with caution and with close laboratory monitoring in patients receiving heparin at the same time, since antithrombin III strengthens heparin's blood-thinning effect and increases the risk of bleeding.

• Antithrombin III should not be used in patients with a known hypersensitivity to the product or any of its ingredients, or in patients with a history of heparin-induced thrombocytopenia.

• Antithrombin III significantly enhances the anticoagulant effect of heparin, so heparin doses usually need to be reduced and clotting status monitored closely when the two are used together; antithrombin III should not be mixed with other medicines in the same solution.

• No interactions between antithrombin III and food have been identified.

• Antithrombin III is given by slow intravenous injection or infusion, reconstituted immediately before use, with dosing and frequency individualized based on antithrombin activity blood tests.

• Antithrombin III is stored refrigerated between 2°C and 8°C, protected from light, and must not be frozen; once reconstituted it should be used right away and not returned to the refrigerator.

• Antithrombin III replaces a natural clot-preventing protein in people whose bodies don't make enough of it, lowering the risk of dangerous blood clots during high-risk periods such as surgery, pregnancy, or delivery; it is given by injection or infusion in a medical setting with regular blood testing to guide dosing, and any signs of allergic reaction should be reported right away.