Antithrombin is a 58kD, 432 amino-acid glycoprotein belonging to the serpin superfamily and is one of the most important natural inhibitors of blood coagulation.
Antithrombin exerts its effect principally on thrombin and Factor Xa. Its activity is greatly enhanced by heparin and the anticoagulant effects of heparin are dependent upon the presence of antithrombin.
The safety and efficacy of antithrombin alfa (rhAT) was assessed in a multicentre study1 involving 13 patients with a personal or family history of deep vein thrombosis (DVT) and previously documented AT activity <60 per cent of normal undergoing elective surgery, delivery or Caesarean section. All patients received intravenous rhAT by continuous infusion to maintain activity between 80 and 120 per cent of normal.
Treatment was initiated prior to the high-risk situation and continued during the high-risk situation, for a minimum of three days. Duplex ultrasound scans to monitor for DVT were performed prior to treatment, then at fixed time points and when clinically indicated. Scans were evaluated both locally and centrally.
None of the patients showed clinical symptoms of DVT or other thromboembolic events during treatment or during the 30-day follow-up period. One patient had documented acute DVT at seven-day follow-up by central but not local evaluation but was asymptomatic throughout and no action was taken. No allergic or anaphylactic reactions and no evidence of antibodies to rhAT were observed during up to 90 days of follow-up.
1. von Depka M, Shaffer D, Baudo F et al. Safety and efficacy of prophylactic intravenous administration of recombinant human antithrombin (rhAT) to hereditary AT deficient patients in high-risk situations. Abstract. Presented at the American Society of Hematology 46th Annual Meeting and Exposition (San Diego), December 2004
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