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Factor VII
See also Coagulation proteins
General information
Factor VII is the most sensitive of the vitamin K-dependent clotting factors. The mode of action is tissue factor-dependent activation of factors Xa and IXa on the surfaces of activated platelets [ ]. Factor Xa leads to thrombin generation and hemostasis, by converting fibrinogen to fibrin. This process is limited to the site of injury, since exposure of tissue factor from the subendothelial matrix has a role in the action of recombinant factor VIIa, thereby reducing the risk of thromboembolic events [ ].
Recombinant activated factor VII (factor VIIa) is indicated for patients with inhibitors of clotting factors VIII and IX [ ]. It has also been used to good effect preoperatively, in patients with severe thrombocytopenia, and in the treatment of life-threatening bleeding, including bleeding related to anticoagulant therapy or liver failure [ ]. The usefulness of recombinant factor VIIa for correcting the prothrombin time has been demonstrated in three neonates with liver failure undergoing liver biopsy and central venous catheter placement [ ].
A disadvantage of recombinant factor VIIa is the need for frequent administration, because of its short half-life, about 2.7 hours with a clearance of 0.5 ml/kg/minute. The clearance is even faster in patients aged under 15 years. In one child the half-life was no more than 1 hour [ ].
In general factor VII is well tolerated, with an incidence of non-serious adverse events of 3.6% [ ]. The most frequently reported adverse events are hypertension, skin reactions, fever, headache, epistaxis, reduced plasma fibrinogen, and prolonged prothrombin time [ , ].
Animal studies and case reports have suggested that recombinant factor VIIa should reduce the INR in patients taking oral anticoagulants and also has a hemostatic effect [ ].
Organs and systems
Cardiovascular
Thrombophlebitis at the infusion site is a common complication of continuous infusion of various clotting factor concentrates and has been noted after infusion of factor VIIa [ , ]. Thrombophlebitis occurred in one of eight hemophiliacs with inhibitors who received continuous infusion of recombinant factor VIIa to allow elective surgery [ ]. In 25 hemophilia patients with inhibitors, who received recombinant factor VIIa for surgical procedures or spontaneous bleeding, there was one case of thrombophlebitis in 35 continuous infusion courses [ ]. In most instances, thrombophlebitis can be prevented by parallel infusion of saline or heparin.
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A 38-year-old patient with hemophilia A with factor VIII inhibitors was treated with recombinant factor VIIa for about 1 month and 18 days after the last infusion developed a distal deep venous thrombosis. An effect of the factor VIIa could not be ruled out, but long-term immobilization and severe infection could have contributed [ ].
Angina pectoris and tachycardia have been reported after the use of recombinant factor VIIa [ ]. Among patients who had more than 2400 treatment episodes with recombinant factor VIIa, there were two cases of acute myocardial infarction [ ]. One of these patients had a history of cardiovascular disease and the other was very overweight and received massive transfusions, human factor VIII, activated prothrombin complex, and finally recombinant factor VIIa to treat severe intra-abdominal bleeding and shock.
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