Infusion of a stable prostacyclin analogue, iloprost, to patients with peripheral vascular disease: lack of antiplatelet effect but risk of thromboembolism
Article Abstract:
Peripheral vascular disease is a condition that is characterized by a reduction in blood flow through blood vessels of the extremities. Reduced blood flow can be caused by a narrowing of the blood vessel or by the formation of blood clots that break free and travel through the circulatory system (thromboembolism). Blood clots are formed when blood cells called platelets become activated and stick together to form clumps. Prostacyclin, a compound produced in the body, is a potent inhibitor of platelet clot formation. However, prostacyclin is not a good treatment for vascular disease because it is chemically unstable and is rapidly broken down. Therefore, a substance similar to prostacyclin called iloprost was developed. The effectiveness of iloprost as an inhibitor of platelet clot formation was evaluated in 13 patients with peripheral vascular disease. The patients were treated with infusions of iloprost, eight hours a day, for three days. Blood samples were analyzed for platelet reactivity (the ability of platelets to form clots), coagulation (the ability of blood to turn from liquid to solid), and thrombolytic activity (ability to dissolve a clot). Blood samples taken one hour after infusion of iloprost showed no changes in thrombolytic activity, while blood coagulation was enhanced. Four out of 13 patients had hyperreactive platelets (increased clot formation). When blood samples were taken during infusion with iloprost, four out of five patients tested had enhanced clot formation and coagulation. Blood samples treated with iloprost in vitro (in a test tube), at the concentration required to produce a therapeutic effect, did not inhibit platelets from forming clots and coagulation was increased. It is concluded that the effectiveness of iloprost in treating vascular disease is not related to an inhibition of platelet function, and that iloprost may increase the risk of thromboembolism. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Medicine
Subject: Health care industry
ISSN: 0002-9343
Year: 1991
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Correlation between lupus anticoagulants and anticardiolipin antibodies in patients with prolonged activated partial thromboplastin times
Article Abstract:
Activated partial thromboplastin time (APTT) is the time required for a clot to form after the blood clotting factor thromboplastin, calcium and a phospholipid are added to a blood sample. Normal values range from 16 to 40 seconds, with prolonged times indicating blood clotting abnormalities. The incidence of thrombosis or blood clotting may be increased in patients with prolonged APTT due to a lupus anticoagulant (LA), an antiphospholipid antibody or specialized protein that specifically binds to and inactivates phosphate-containing compounds. The antiphospholipid antibodies can be measured using an immunological test called the enzyme-linked immunoabsorbent assay (ELISA) that uses cardiolipin as the phospholipid. However, studies have not consistently shown a correlation between direct measurements of LA and results from cardiolipin-dependent ELISA or an association between anticardiolipin antibodies (ACA) and thrombosis. The sensitivity and specificity of an LA assay for detecting ACA was evaluated in 70 patients with a prolonged APTT. The LA assay was shown to be 94 percent sensitive and 87 percent specific for detecting ACA. ACA were detected in 75 percent of 12 patients with thrombosis and 14 percent of 35 patients without thromboses. Patients with LA due to infection or medication had no thrombosis. The findings demonstrate that a test for LA in patients with prolonged APTT is sensitive and specific for measuring ACA levels, which may indicate the risk for thromboses in patients with LA unrelated to infection or medication. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Medicine
Subject: Health care industry
ISSN: 0002-9343
Year: 1990
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