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Drugs affecting
blood coagulation
Learning objectives
Upon completion of this chapter, you should be able to:
1.
Outline the mechanisms by which blood clots dissolve in the body, correlating this information with the
actions of drugs used to affect blood clotting.
2.
Describe the therapeutic actions, indications, pharmacokinetics, contraindications, most common adverse
reactions and important drug–drug interactions associated with drugs affecting blood coagulation.
3.
Discuss the use of drugs that affect blood coagulation across the lifespan.
4.
Compare and contrast the prototype drugs aspirin, heparin and antihaemophilic factor with other agents
used to affect blood coagulation.
5.
Outline the care considerations, including important teaching points, for people receiving drugs used to
affect blood coagulation.
Glossary of key terms
anticoagulants:
drugs that block or inhibit any step of the coagulation process, preventing or slowing clot formation
antiplatelet agents:
drugs that interfere with the aggregation or clumping of platelets to form the platelet plug
clotting factors:
substances formed in the liver—many requiring vitamin K—that react in a cascading sequence to cause the
formation of thrombin from prothrombin; thrombin then breaks down fibrin threads from fibrinogen to form a clot
coagulation:
the process of blood changing from a fluid state to a solid state to plug injuries to the vascular system
extrinsic pathway:
cascade of clotting factors in blood that has escaped the vascular system to form a clot on the outside of the
injured vessel
haemorrhagic disorders:
disorders characterised by a lack of clot-forming substances, leading to states of excessive bleeding
haemostatic agents:
drugs that stop blood loss, usually by blocking the plasminogen mechanism and preventing clot dissolution
Hageman factor:
first factor activated when a blood vessel or cell is injured; starts the cascading reaction of the clotting factors,
activates the conversion of plasminogen to plasmin to dissolve clots and activates the kinin system responsible for the activation
of the inflammatory response
intrinsic pathway:
cascade of clotting factors leading to the formation of a clot within an injured vessel
plasminogen:
natural clot-dissolving system; converted to plasmin (also called fibrinolysin) by many substances to dissolve clots that
have formed and to maintain the patency of injured vessels
platelet aggregation:
property of platelets to adhere to an injured surface and then attract other platelets, which clump together or
aggregate at the area, plugging up an injury to the vascular system
thromboembolic disorders:
disorders characterised by the formation of clots or thrombi on injured blood vessels with potential
breaking of the clot to form emboli that can travel to smaller vessels, where they become lodged and occlude the vessel
thrombolytic agents:
drugs that lyse, or break down, a clot that has formed; these drugs activate the plasminogen mechanism to
dissolve fibrin threads
Test your current knowledge of drugs affecting blood coagulation with a PrepU Practice Quiz!
Simulation-based learning
On completion of the chapter, consider the scenario of Carl Shapiro (Part 1) who arrives in the emergency department.
Consider the medication management of Carl’s condition, as it relates to your learning in this chapter.
Then, work through the second scenario of Vernon Watkins (Part 2) who underwent a hemicolectomy 5 days ago and
now has abdominal and leg pain. Consider how the concepts learnt in this chapter relating to medication management
apply to his case.
