Anticoagulants

1. 23 Anticoagulants

2. Multimedia Directory Slide 17 Mechanism of Action of Heparin Animation Slide 25 Mechanism of Action of Warfarin Animation

3. Hemostasis: Three Events After Injury • Vascular spasms: platelets release serotonin, which causes blood vessel to spasm and decrease blood loss until clotting occurs • Platelet plug: platelets become sticky and adhere to vessel lining and each other, forming platelet plug, which is invaded by clotting factors

4. Hemostasis: Three Events After Injury • Coagulation: clot forms through chemical reactions that create netlike structure of fibrin, sealing off opening in injured vessel

5. Figure 23-1 Hemostasis begins when a blood vessel is damaged and ends when the fibrin threads trap blood cells, forming a clot that seals the injured vessel.

6. Figure 23-2 Basic steps of hemostasis.

7. Mechanism of Action: Hemostasis • Involves 11 plasma proteins (clotting factors) • Most clotting proteins synthesized by liver • Prothrombin activator, prothrombin, thrombin, fibrinogen, fibrin

8. Figure 23-3 The steps in the coagulation cascade.

9. Anticoagulants • Medications that prolong bleeding time • Do not dissolve clots already formed, but may prevent clots from becoming larger • Used to treat MI, venous thrombosis, pulmonary emboli • Primarily used for thrombosis in veins

10. Table 23-1 Anticoagulants

11. Heparin: Uses • Works by increasing length of coagulation; inhibits thrombi from forming or growing larger • Treat emboli, thrombi, MI, and to prevent clotting during open-heart surgery, coronary artery bypass graft, and dialysis

12. Heparin: Adverse Effects • Hemorrhage in urinary or GI tracts, subdural hematomas, hemorrhagic pancreatitis, hemarthrosis, ecchymosis

13. Heparin: Contraindications • Contraindicated in serious and intracranial bleeding, severe liver or kidney disease, malignant hypertension • Interacts with aspirin, NSAIDs, anesthetics, valproic acid, thrombolytics, and other drugs

14. Heparin: Patient Information • Teach patients how to administer heparin subcutaneously. • Advise patients to protect themselves from injury (e.g., use electric shaver). • Warn patients to avoid aspirin and other OTC drugs. • Instruct patients to report signs of bleeding.

15. Heparin in Older Adults • Older adults are more susceptible to effects of anticoagulants. Signs of overdose include epistaxis, blood in stool or urine, excessive bruising, and prolonged bleeding. • Overdose can be treated by slow infusion of 1% protamine sulfate.

16. Figure 23-4 Mechanism of action of anticoagulants.

17. Mechanism of Action of Heparin Animation Click on the screenshot to view an animation showing the mechanism of action of heparin. Back to Directory

18. LMWH: Uses • Greater bioavailability and longer action than heparin • More effective in preventing and treating venous thromboembolism • Less bleeding and fewer episodes of heparin-induced thrombocytopenia

19. Table 23-2 Common Low-Molecular-Weight Heparins

20. Warfarin (Coumadin): Uses • Interferes with hepatic synthesis of vitamin K-dependent clotting factors (II, VII, IX, X) • Used on inpatient and outpatient basis for long-term anticoagulation

21. Warfarin: Adverse Effects • Hemorrhage • Diarrhea • Urticaria • Alopecia • Skin necrosis • Dermatitis

22. Warfarin: Contraindications • Contraindicated in active or previous ulceration, hepatic or renal disease, malignant hypertension, bacterial endocarditis, chronic alcoholism, pregnancy • Interacts with hepatic enzyme inhibitors, aspirin, NSAIDs, and thrombolytics

23. Warfarin: Patient Information • Instruct patients to report signs of bleeding; chest, abdominal, lumbar, or pelvic pain. • Advise patient to stop drug immediately if signs of hepatitis occur. • Advise female patients to avoid pregnancy with barrier contraceptive and to avoid breastfeeding.

24. Warfarin Tips for Patients • Advise patients that 5 days prior to dental procedures, warfarin should be stopped. • Supplemental intake of vitamin K can potentiate or inhibit oral anticoagulants.

25. Mechanism of Action of Warfarin Animation Click on the screenshot to view an animation showing the mechanism of action of warfarin. Back to Directory

26. Antiplatelets: Uses • Prevent platelets from binding together • Used to prevent clot formation in arteries, in MI and stroke, and in PCTA • Aspirin: low doses inhibit platelet aggregation and prolong bleeding time • Ticlopidine (Ticlid) and clopidogrel (Plavix) irreversibly inhibit platelet activation

27. Antiplatelets: Uses • Abciximab (ReoPro), eptifibatide (Integrilin) and tirofiban (Aggrastat) interrupt interaction of fibrinogen with clotting factors

28. Table 23-3 Antiplatelet Agents

29. Antiplatelets: Adverse Effects • Epigastric pain, heartburn, nausea, diarrhea, major or minor bleeding • Abciximab: cardiac arrhythmias, abnormal thoughts, dizziness

30. Antiplatelets: Contraindications • Contraindicated in patients with history of peptic ulcer, hypertension, asthma, allergies, nasal polyps • Interact with anticoagulants, thrombolytic agents, dextran, and other drugs

31. Antiplatelets: Patient Information • Instruct patients to report nausea, diarrhea, rash, sore throat, or infections; signs of bleeding; signs of hepatitis. • Advise patients to avoid aspirin and antacids.

32. Garlic as Anticoagulant • Garlic has been shown to decrease platelet aggregation. • Use of garlic with anticoagulants may increase risk of bleeding complications.

33. Thrombolytics: Uses • Used to prevent or treat excessive bleeding from surgical sites • Facilitate conversion of plasminogen to plasmin, which hydrolyzes fibrin to dissolve blood clots • Also called plasminogen activators

34. Table 23-4 Thrombolytics

35. Thrombolytics: Adverse Effects • Common: bleeding caused by fibrinogenolysis or fibrinolysis at site of injury • Serious: intracranial bleeding

36. Thrombolytics: Contraindications • Contraindicated in active bleeding, pregnancy, lactation, intracranial trauma, vascular disease, and cancer • Interact with anticoagulants, aspirin, and herbs such as feverfew, ginger, and ginkgo

37. Thrombolytics: Patient Information • Instruct patients to report signs of bleeding or changes in consciousness. • Advise women to avoid breastfeeding.

38. Thrombocytopenia • Platelet deficiency; most common cause of abnormal bleeding • Hemophilia applies to several hereditary bleeding disorders that result from lack of factors needed for clotting.