Pharmacology in Hematology

1. Pharmacology in Hematology Developed by: Dawn Johnson, RN, MSN, Ed

2. Hemostasis - Process of Stopping the Flow of Blood • Internally and externally • Prevent bleeding from wounds which could lead to shock or even death

3. Three Basic Steps to Hemostasis • Injured vessel constricts to slow blood flow • Platelets adhere to injured area and aggregate, plugging damaged vessel • Coagulation cascade occurs thus forming insoluble fibrin strands which slows blood flow more

4. Coagulation Cascade - Series of Complex Steps • Injured cells release prothrombin activator • Prothrombin activator changes prothrombin to thrombin • Thrombin changes fibrinogen to fibrin • Fibrin forms an insoluble web over injured area which stops blood flow

5. Coagulation-Modifier Drugs • Anticoagulants • Thrombolytics • Hemostatics

6. Anticoagulants - Prevent the Formation of Clots • Inhibiting specific clotting factors in the coagulation cascade • Diminishing the clotting action of platelets • Both ways increase the time to form clots

7. Thrombolytics • Dissolve life-threatening clots

8. Hemostatics • Promote formation of clots • Inhibit removal of fibrin

9. Anticoagulants Prevent the Formation and Enlargement of Clots • Examples - heparin (Heplock), warfarin (Coumadin) • Mechanism of action - inhibit specific clotting factors which interfere with coagulation cascade in order to prevent formation or enlargement of clot • Primary use - thromboembolic disease; prevent formation of clots in veins • Adverse effects - abnormal bleeding

10. Antiplatelet Agents Prolong Bleeding Time by Interfering with Platelet Aggregation • Example - ticlopidine (Ticlid) • Mechanism of actions • Aspirin: inhibits thromboxane2, which prevents aggregation of platelets • ADP receptor blockers: interfere with platelet plasma membrane, which prevents platelet aggregation • Glycoprotein IIb/IIIa inhibitors: glycoprotein IIb/IIIa enzyme inhibited which prevents platelet aggregation

11. Antiplatelet Agents Prolong Bleeding Time by Interfering with Platelet Aggregation (cont’d) • Primary uses - prevent clot formation in arteries • Adverse effects - abnormal bleeding; reduce number of neutrophils

12. Thrombolytics Are Used to Dissolve Existing Clots • Example - alteplase (Activase) • Mechanism of action - convert plasminogen to plasmin which causes fibrin to degrade, then preexisting clot dissolves • Primary uses - acute MI, pulmonary embolism, acute ischemic CVA, DVT, arterial thrombosis, coronary thrombosis, clear thrombi in arteriovenous cannulas and blocked IV catheters • Adverse effects - abnormal bleeding; contraindicated in patients with active bleeding or recent trauma

13. Hemostatics Are Used to Promote the Formation of Clot • Example - aminocaproic (Amicar) • Mechanism of action - prevent fibrin from dissolving, which enhances stability of the clot • Primary use - prevent and treat excessive bleeding from surgical sites • Adverse effects - none listed

14. Hematinic Drugs

15. Function of Hematinic drugs • Provide essential building blocks for RBC production. • They do so by increasing hemoglobin which is necessary for oxygen transportation

16. Types • Iron • Vitamin B12 • Folic Acid

17. Iron • Used to treat the most common form of anemia-iron defieciency. • One function of iron-production of hemoglobin. • Treatment is usually 6 months • Parenteral iron therapy is used for patients who can’t absorb oral preparations, aren’t compliant with oral treatment, or have bowel d/o

18. Drug Interactions • Iron is reduced by antacids as well as foods such as coffee, tea, eggs, and milk. • Other drug interactions are: Tetracycline or any of the cycline drugs, methlydopa, ciprofloxacin, oloxacin, chloramphenicol, and pencillamine may be reduced. • Cimetidine and other histamine2-receptor antagonists may decrease GI absorption of iron.