Affect the Clotting Cascade

The clotting cascade. Circles denote vitamin K dependent clotting factors, ovals are clotting factors affected by endothelial cell factors (e.g., thrombomodulin). Starred factors are inhibited by the actions of heparin and antithrombin III. 

An anticoagulant is a drug that disrupts the clotting cascade, thus inhibiting clot formation. It does not affect platelets, nor does it have an appreciable effect on an established clot. 

An antithrombotic drug is one that affects platelets. These drugs decrease platelet aggregation, and affect the activation of platelets, thus decreasing the initiation of the clotting cascade. 

The conformational change in antithrombin III induced by heparin allows the molecule to bind to, and inactivate, factors involved in the clotting cascade. Primary factors affected are the activated forms of factor IX ( Christmas factor, or plasma thromboplastin component) and X ( Stuart-Prower factor ). 

Both drugs have an indirect action on the clotting cascade—heparin must form a complex with antithrombin III in order to produce an effect, and warfarin acts through depletion of vitamin K, which affects specific clotting factors. 

Heparin and warfarin are anticoagulants that affect activation or formation of proteins in the clotting cascade. Lepirudin is an inhibitor of thrombin, and aminocaproic acid is an inhibitor, not an activator, of fibrinolysis and the conversion of plasminogen to plasmin. Reteplase is the only thrombolytic drug listed. The answer is (D). 

Besides the changes in wettability, they found that the hemocompatibility was significantly affected by plasma treatment. Treatment of PDMS with both Ar and O2 induced a decrease in hemocompatibility, leading to shorter clotting times. The N2 and NH3 treatments had a significantly beneficial effect on the activation of the coagulation cascade. 

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