Drugs for Coagulation Disorders 20 Drugs for Coagulation Disorders

Learning Outcomes Explain the importance of hemostasis. Construct a flow chart diagramming the important steps of hemostasis and fibrinolysis. Describe the types of disorders for which coagulation modifier drugs are prescribed. Identify the primary mechanisms by which coagulation modifier drugs act.

Learning Outcomes For each of the classes in the Drug Snapshot, identify representative drugs, explain their mechanisms of action, primary actions, and important adverse effects. Categorize coagulation modifier drugs based on their classifications and mechanisms of action.

Core Concept 20.1 Hemostasis is a complex process involving multiple steps and many clotting factors. Hemostasis is the balance between clot formation and clot breakdown

Coagulation Everyone is familiar with simple cuts and scraps and we all take for granted that they will stop bleeding in a few minutes.

Basic steps in hemostasis

Major steps in the coagulation cascade

Coagulation Cascade This process normally takes about 6 minutes Vitamin K is required for the liver to produce these clotting factors Liver disease can greatly effect coagulation

Removing a blood clot is essential to restoring normal circulation. Core Concept 20.2 Removing a blood clot is essential to restoring normal circulation.

Primary steps in fibrinolysis

Fibrinolysis

Clots Once a stationary clot forms (thrombus), it often grows larger as more fibrin is added. Pieces of the clot may break off and travel in the blood stream to possibly lodge elsewhere. A traveling clot is know as an embolus When clots or emboli form, drug therapy becomes necessary.

Deep Vein Thrombosis/Embolus

Drugs are used to modify the coagulation process. Core Concept 20.3 Drugs are used to modify the coagulation process.

Drugs Anticoagulants used to prevent the formation of clots Inhibit specific clotting factors in the coagulation cascade or diminish the clotting action of platelets Increase the normal time the body takes to form clots

“Blood Thinners” This is an incorrect term; However, it is commonly used. The drugs do not change the thickness of the blood, just inhibits the clotting cascade

Drugs Thrombolytics used to dissolve such life-threatening clots. Hemostatics used to speed clot formation, or to limit bleeding from a surgical site.

Anticoagulants prevent the formation and enlargement of clots. Core Concept 20.4 Anticoagulants prevent the formation and enlargement of clots.

Anticoagulants Actions Adverse effect is bleeding. Inhibit certain clotting factors Lengthen clotting time Prevent thrombi from forming or growing larger Adverse effect is bleeding. Specific blockers administered to reverse the anticoagulant effects

Primary Anticoagulants heparin (Hep-Lock warfarin (Coumadin) Coumadin therapy can overlap heparin therapy Do not give ASA with these drugs RANDI Precautions

Antidotes: Anticoagulants Protamine sulfate is used for heparin Vitamin K is administered for warfarin.

Vitamin K Foods high in Vitamin K can reverse the action of warfarin (Coumadin) Green leafy vegetables Milk and milk products Some cereals Orange juice Cauliflower Cucumbers

Laboratory Tests Oral Anticoagulants Prothrombin time (PT) Normal range for PT is 12 to 15 seconds Prolonged with anticoagulant treatment. International Normalized Ratio (INR) Method of performing PT tests varies from laboratory to laboratory

Laboratory Tests Oral Anticoagulants This is PT multiplied by a correction factor. Recommended post-treatment INR values range from 2 to 4.5.

Mechanism of action of anticoagulants

Adverse Effects Most common and potentially serious adverse effect is bleeding. Signs: Bruising Bleeding gums Nosebleed Blood in urine or stool

Signs of Bleeding

Core Concept 20.5 Antiplatelet agents prolong bleeding time by interfering with platelet aggregation.

Antiplatelet Agents Used to prevent clot formation in arteries. Three primary subclasses of antiplatelet agents Aspirin Adenosine diphosphate (ADP) receptor blockers Glycoprotein IIb/IIIa receptor blockers.

Thrombolytics are used to dissolve existing clots. Core Concept 20.6 Thrombolytics are used to dissolve existing clots.

Thrombolytics Prescribed for disorders in which a clot has already formed, including the following: Acute MI Pulmonary embolism Cerebrovascular accident (CVA) DVT

Thrombolytics Prescribed for disorders in which a clot has already formed, including the following: Arterial thrombosis Coronary thrombosis To clear thrombi in arteriovenous cannulas and blocked IV catheters

Hemostatics are used to promote the formation of clots. Core Concept 20.7 Hemostatics are used to promote the formation of clots.