Clotting and Anti-Clotting Agents Flashcards
Ticagrelor is an anti-platelet drug used to treat STEMI. Explain its mechanism of action.
Ticagrelor is an allosteric antagonist of ADP receptors, therefore it reversibly inhibits platelet aggregation.
Aspirin is used to treat STEMI and stroke. Explain why.
Aspirin irreversibly inhibits the cyclooxygenase enzyme (COX), which is needed to synthesise thromboxanes. Aspirin thus inhibits thromboxane production, which reduces platelet aggregation.
Why is unfractionated heparin given to STEMI and DVT patients? What is an alternative form of heparin that is used for DVT?
UFH activates antithrombin III (AT), which is an enzyme inhibitor. The activated AT then inactivates thrombin, factor Xa and other coagulation factors, preventing clotting.
Dalteparin is a low-molecular weight heparin that is also used to treat DVT.
What is fondaparinux used to treat? What is its mechanism of action, and how does this differ from that of heparin?
Fondaparinux is given to STEMI patients to prevent clotting. The drug selectively inhibits Factor Xa, as opposed to heparin which inhibits a number of factors via activation of antithrombin.
Tissue plasminogen activator (tPA) is used to treat stroke patients. Explain why.
tPA converts plasminogen into plasmin, which is biologically active. Plasmin breaks down insoluble fibrin into soluble fibrin fragments, thus dissolving blood clots.
Why is dipyridamole given to some patients with a history of stroke?
Dipyridamole inhibits the phosphodiesterase enzymes that break down cAMP and inhibits cellular reuptake of adenosine. This reduces platelet aggregation via ADP. Dipyridamole also increases the release of tPA in the brain, making it useful for dissolving thrombi that cause strokes.
What is rivaroxaban used to treat and how does it work?
Rivaroxaban is a highly selective direct Factor Xa inhibitor. It therefore inhibits the activation of thrombin and the formation of thrombi.
Explain the use of warfarin and its mechanism of action.
Warfarin is an anticoagulant used to treat DVT. It works by inhibiting the vitamin K-dependent synthesis of the clotting factors II (prothrombin), VII, IX and X.
