1. ANTI-COAGULANTS DR.UZMA RIAZ

2. Thrombosis Venous thrombosis is associated with stasis of blood Venous thrombosis is associated with stasis of blood Has small platelet component and large component of fibrin Has small platelet component and large component of fibrin Arterial thrombosis is associated with atherosclerosis Arterial thrombosis is associated with atherosclerosis -initiated due to endothelial injury leads to atheromatous plaque formation Plaque rupture, platelet adhesion, activation, aggregation initiates thrombus growth Plaque rupture, platelet adhesion, activation, aggregation initiates thrombus growth Thrombus has large platelet component Thrombus has large platelet component Arterial thrombus may break away, emboli form leads to ischemia and infarction Arterial thrombus may break away, emboli form leads to ischemia and infarction

3. Hemostasis Spontaneous Arrest of Bleeding from a Damaged Blood Vessel; This occurs by the following steps Spontaneous Arrest of Bleeding from a Damaged Blood Vessel; This occurs by the following steps 1. Vasospasm 2. Platelet Adhesion 3. Platelet Aggregation 4. Platelet Plug 5. Fibrin Reinforcement of platelet plug

4. Coagulation This is the conversion of blood in the liquid form to a solid gel or clot. Normally there is a balance between Procoagulants (thromboxane, thrombin, activated platelets etc.) and Anti-coagulants (heparan sulfate, Antithrombin III, Nitric oxide and Prostacyclin) Whenever this balance is disturbed coagulation occurs: Procoagulants > Anticoagulants Procoagulants > Anticoagulants Injury to blood vessel Injury to blood vessel Blood stasis Blood stasis

5. Clotting Factors I - Fibrinogen I - Fibrinogen II - Prothrombin II - Prothrombin III - Tissue Thromboplastin III - Tissue Thromboplastin IV - Calcium IV - Calcium V - Proaccelerin V - Proaccelerin VII - Proconvertin VII - Proconvertin VIII- Antihemophilic globulin VIII- Antihemophilic globulin IX - Christmas Factor IX - Christmas Factor X - Stuart Power Factor X - Stuart Power Factor XI - Plasma Thromboplastin anticedent (PTA) XI - Plasma Thromboplastin anticedent (PTA) XII - Hageman Factor XII - Hageman Factor XIII -Fibrin-stabilizing factor XIII -Fibrin-stabilizing factor

6. INITIATION OF BLOOD COAGULATION Extrinsic Pathway Tissue trauma Tissue trauma Leakage of Tissue Factor Leakage of Tissue Factor XXa Prothrombin activator Ca +2, factor VII Ca +2 Prothrombin Thrombin (factor II) Ca +2 Intrinsic Pathway Blood trauma/ contact with collagen Activation of factor XII, IX, VIII XXa Ca +2 Prothrombin activator activator Prothrombin Thrombin (factor II) Activation of certain factors (VII, II, X and protein C and S) is essential for coagulation. This activation requires vit K (reduced form)

7. Classification A. Parenteral Anti-Coagulants 1. Indirect Thrombin Inhibitors a) Heparins i) High Molecular Weight Heparin i) High Molecular Weight Heparin Unfractionated Heparin (UFH) ii) Low Molecular Weight Heparins ii) Low Molecular Weight Heparins EnoxaparinDalteparin TinzaparinReviparin Danaparoid

8. 2. Direct Thrombin Inhibitors 2. Direct Thrombin Inhibitors HirudinLepirudin BivalirudinArgatroban B. Oral Anti-Coagulants B. Oral Anti-Coagulants 1. Coumarins WarfarinDicumarol 2. Indanediones Phenindione

9. Heparin,History McLean, a 2 nd year medical student attempting to extract coagulant substances from various tissues during a vacation project. But found instead a powerful anticoagulant. He discovered in 1916 that liver contains a powerful anticoagulant. McLean, a 2 nd year medical student attempting to extract coagulant substances from various tissues during a vacation project. But found instead a powerful anticoagulant. He discovered in 1916 that liver contains a powerful anticoagulant. Howell and Holt in 1918 named it heparin because it was obtained from liver Howell and Holt in 1918 named it heparin because it was obtained from liver Occurs in mast cells (richest source of mast cells are lungs, liver and intestinal mucosa) Occurs in mast cells (richest source of mast cells are lungs, liver and intestinal mucosa) Commercial heparin is extracted from porcine intestinal mucosa and bobine lung Commercial heparin is extracted from porcine intestinal mucosa and bobine lung It is a mixture of straight chain anionic (negative charge) glycosaminoglycan with a wide range of molecular weights It is a mixture of straight chain anionic (negative charge) glycosaminoglycan with a wide range of molecular weights It is strongly acidic because of presence of sulfate and carboxylic acid groups It is strongly acidic because of presence of sulfate and carboxylic acid groups

10. Heparin-Kinetics Heparin is highly charged, thus crosses cell membranes very poorly, hence given Parenterally Heparin is highly charged, thus crosses cell membranes very poorly, hence given Parenterally Low dose: Subcutaneous Low dose: Subcutaneous High Dose: Subcutaneous or IV Injection High Dose: Subcutaneous or IV Injection Metabolized by liver, half life depends on dose Metabolized by liver, half life depends on dose

11. Heparin-Mechanism of Action Once the coagulation pathways are activated, factors IXa, Xa, XIa, XIIa and IIa (especially IIa,IXa,Xa), need to be neutralized by Anti-thrombin III (AT III). Once the coagulation pathways are activated, factors IXa, Xa, XIa, XIIa and IIa (especially IIa,IXa,Xa), need to be neutralized by Anti-thrombin III (AT III). Heparin accelerates the interaction of the active clotting factors with AT III. Heparin accelerates the interaction of the active clotting factors with AT III. The negatively charged heparin molecule binds to the positively charged lysine sites on AT III The negatively charged heparin molecule binds to the positively charged lysine sites on AT III This causes a conformational change in AT III and exposing its active arginine site This causes a conformational change in AT III and exposing its active arginine site The serine active sites of the active clotting factors bind to the reactive arginine site of AT III The serine active sites of the active clotting factors bind to the reactive arginine site of AT III The resulting complex is removed by the reticuloendothelial system The resulting complex is removed by the reticuloendothelial system This process is accelerated 1000-3000 times by heparin This process is accelerated 1000-3000 times by heparin The active heparin molecules bind tightly to antihormbin and cause a conformational change in this inhibitor. The conformational change of antithrombin exposes its active site for more rapid interaction with the proteases (the activated clotting factors) Heparin functions as a cofactor for the antithrombin protease reactio without being consumed. Once the antithrombin protease complex is formed, heparin is released intact for renewed binding to more antithrombin. The active heparin molecules bind tightly to antihormbin and cause a conformational change in this inhibitor. The conformational change of antithrombin exposes its active site for more rapid interaction with the proteases (the activated clotting factors) Heparin functions as a cofactor for the antithrombin protease reactio without being consumed. Once the antithrombin protease complex is formed, heparin is released intact for renewed binding to more antithrombin.

12. Heparin catalyzes the reaction without being consumed Heparin catalyzes the reaction without being consumed Once antithrombin-clotting factor complex is formed, heparin is released for renewed binding to more antithrombin Once antithrombin-clotting factor complex is formed, heparin is released for renewed binding to more antithrombin High molecular weight Heparins accelerates the inactivation of clotting factors IIa and Xa. High molecular weight Heparins accelerates the inactivation of clotting factors IIa and Xa. Low molecular weight heparins accelerate the inactivation of only Factor Xa Low molecular weight heparins accelerate the inactivation of only Factor Xa

13. Mechanism No heparin Active clotting factors Slow Antithrombin III Inactive clotting factors Heparin Active clotting factors Fast Antithrombin III + Heparin Heparin Inactive clotting factors

17. Character HMW Heparins LMW Heparins Molecular Weight High (30000 Daltons) Low (5000 Daltons) BiotransformationLow High (90%) Half Life Shorter-depends on dose Longer-independent of dose Mechanism of Action Inactivate both factor IIa and factor Xa Inactivate both factor IIa and factor Xa Inactivate only factor Xa Anti-coagulant effect More effective less effective

18. Monitoring By aPTT Can be given once or twice daily without monitoring, but requires special assay if necessary AdverseEffects Less chance of thrombocytopenia and long term osteoporosis Excretion Cleared by the Reticuloendothelial system Cleared unchanged by kidneys Reversal By protamine Not fully reversed by protamine Expense Not expensive Expensive

19. DoseResponse Less predictable dose response because of binding to plasma proteins, macrophages and endothelial cells Has a more predictable dose-response because it does not bind to plasma proteins, macrophages, or endothelial cells. Use More effective for a) Orthopaedic procedures on lower limb b) Pulmonary Embolism c) Unstable Angina

20. Advantages of LMWH over UFH Better subcutaneous bioavailability(70-90%) compared to UFH(20- 30%) Better subcutaneous bioavailability(70-90%) compared to UFH(20- 30%) Longer and more consistent half life: once daily subcutaneous administration Longer and more consistent half life: once daily subcutaneous administration Since aPTT/clotting times are not prolonged, lab. monitoring is not needed Since aPTT/clotting times are not prolonged, lab. monitoring is not needed Lower incidence of haemorrhagic complications Lower incidence of haemorrhagic complications Appear to have lesser antiplatelet action so less interference with haemostasiss Appear to have lesser antiplatelet action so less interference with haemostasiss

21. Uses of Heparin (Anti-coagulants in General) 1.Treatment & Prevention of Deep Venous Thrombosis in Bedridden (Immobilized patients) Bedridden (Immobilized patients) Old people Old people Post-operative Post-operative Post-stroke patients Post-stroke patients Leg fractures Leg fractures Elective Surgery Elective Surgery

22. 2. Ischemic Heart Disease Unstable angina After MI After angioplasty CABG, stent replacement; Prevent recurrence 3. Rheumatic Heart Disease/ Atrial Fibrillation Warfarin, heparin, low dose aspirin, Decrease stroke due to emboli

23. 4. Cerebrovascular Diseases Cerebral Emboli (Prevention of recurrence) 5. Vascular Surgery, Prosthetic heart valves, Hemodialysis To prevent thromboembolism 6. DIC Abruptio placenta, malignancies, infections; increased consumption of clotting factors

24. Adverse Effects 1.Bleeding(most common) 2. Allergy and Anaphylaxis 3. Increased hair loss, alopecia 4. Long term-Osteoporosis, spontaneous fractures 5. Thrombocytopenia

25. Heparin-induced Thrombocytopenia HIT) 2 nd most common side effect after bleeding 2 nd most common side effect after bleeding Occurs in 3-5% of patients 5 to 10 days after initiation of therapy of standard heparin Occurs in 3-5% of patients 5 to 10 days after initiation of therapy of standard heparin Lower incidence in low molecular wt heparin. Lower incidence in low molecular wt heparin. In 1/3 of pts is preceded by thrombosis In 1/3 of pts is preceded by thrombosis Can be life-threatening. Can be life-threatening. Due to production of IgG against complexes of heparin with platelet (platelet factor 4) Due to production of IgG against complexes of heparin with platelet (platelet factor 4) The complexes activate more platelets with the release of more platelet factor 4 or other cytokines. The complexes activate more platelets with the release of more platelet factor 4 or other cytokines. This stimulates the formation of more IgG. This stimulates the formation of more IgG. This snow-ball effect uses up platelets and also leads to thrombosis. Systemic bleeding and localized infarction (due to thrombosis) occur. This snow-ball effect uses up platelets and also leads to thrombosis. Systemic bleeding and localized infarction (due to thrombosis) occur.

26. Once thrombocytopenia is determined, heparin must be stopped. Direct thrombin inhibitor should be given Once thrombocytopenia is determined, heparin must be stopped. Direct thrombin inhibitor should be given Platelets must NOT be given because they will react with antibody already being produced against them, causing greater chance of thrombosis. Platelets must NOT be given because they will react with antibody already being produced against them, causing greater chance of thrombosis. 3

27. Heparin and Pregnancy Heparin does not cross the placenta, therefore it must be used instead of warfarin in cases of requiring anticoagulant therapy in pregnancy. Heparin does not cross the placenta, therefore it must be used instead of warfarin in cases of requiring anticoagulant therapy in pregnancy. Warfarin crosses the placenta and induces changed in the fetus to produce the fetal warfarin syndrome – not good. Warfarin crosses the placenta and induces changed in the fetus to produce the fetal warfarin syndrome – not good.

28. Contraindications 1. Hypersensitivity 2. Bleeding Disorders like Hemophilia 3. Thrombocytopenia 4-. Intracranial Hemorrhage 5. GIT Ulcerations 6. Threatened abortion 7. Advanced renal or hepatic disease

29. Antidote –Protamine Sulfate Protamine is a highly basic peptide that combines with heparin as an ion pair to form a stable complex devoid of anticoagulant activity Protamine is a highly basic peptide that combines with heparin as an ion pair to form a stable complex devoid of anticoagulant activity Hemorrhage – can be reversed by protamine sulfate titrated so that 1 mg of protamine sulfate is administered for every 100 U of heparin remaining in the patient. Hemorrhage – can be reversed by protamine sulfate titrated so that 1 mg of protamine sulfate is administered for every 100 U of heparin remaining in the patient. Protamine sulfate is also an anticoagulant because it interacts with platelets, fibrinogen, and other clotting factors – so it can make hemorrhage worse if more is given than necessary. Protamine sulfate is also an anticoagulant because it interacts with platelets, fibrinogen, and other clotting factors – so it can make hemorrhage worse if more is given than necessary.

30. Direct Thrombin Inhibitors (DTIs) The DTIs bind thrombin without additional binding proteins, such as anti-thrombin, and they do not bind to other plasma proteins such as platelet factor 4. The DTIs bind thrombin without additional binding proteins, such as anti-thrombin, and they do not bind to other plasma proteins such as platelet factor 4. Hirudin and Bivalirudin bind at both the catalytic or active site of thrombin as well as at a substrate recognition site Hirudin and Bivalirudin bind at both the catalytic or active site of thrombin as well as at a substrate recognition site Argatroban bind only at the thrombin active site Argatroban bind only at the thrombin active site

31. Lepirudin Monitored by aPTT Monitored by aPTT Action independent of antithrombin Action independent of antithrombin Use in thrombosis related to heparin induced thrombocytopenia Use in thrombosis related to heparin induced thrombocytopenia No antidote No antidote Adverse effect: Antibody formation against thrombin-lepirudin complex Adverse effect: Antibody formation against thrombin-lepirudin complex

32. Bivalirudin: Inhibits platelet activation also Use in percutaneous coronary angiography Argatroban: Used in heparin induced thrombocytopenia with or without thrombosis Monitored by aPTT Dose reduction in liver disease

33. Oral Anti-Coagulants,History Following the report of a hemorrhagic disorder in cattle that resulted from the ingestion of spoiled sweet clover silage, Campbell and Link, in 1939, identified the hemorrhagic agent as bishydroxycoumarin (dicoumarol). Following the report of a hemorrhagic disorder in cattle that resulted from the ingestion of spoiled sweet clover silage, Campbell and Link, in 1939, identified the hemorrhagic agent as bishydroxycoumarin (dicoumarol). In 1948, a more potent synthetic congener was introduced as an extremely effective rodenticide; the compound was named warfarin as an acronym derived from the name of the patent holder, Wisconsin Alumni Research Foundation. In 1948, a more potent synthetic congener was introduced as an extremely effective rodenticide; the compound was named warfarin as an acronym derived from the name of the patent holder, Wisconsin Alumni Research Foundation. Warfarin's potential as a therapeutic anticoagulant was recognized but not widely accepted, partly due to fear of unacceptable toxicity. Warfarin's potential as a therapeutic anticoagulant was recognized but not widely accepted, partly due to fear of unacceptable toxicity. However, in 1951, an Army inductee uneventfully survived an attempted suicide with massive doses of a preparation of warfarin intended for rodent control. However, in 1951, an Army inductee uneventfully survived an attempted suicide with massive doses of a preparation of warfarin intended for rodent control. Since then, these anticoagulants have become a mainstay for prevention of thromboembolic disease Since then, these anticoagulants have become a mainstay for prevention of thromboembolic disease

34. Wisconsin Alumni Research Foundation Coumarin--Warfarin Warfarin-Pharmacokinetics 1. Rapidly and completely absorbed after oral administration 2. 100% Bioavailability 3. Highly plasma protein bound (99%) 4. Crosses the placenta (teratogenic) 5. Appears in milk; infants given Vitamin K 6. Variable but slow clearance;depends on hepatic P450s 7. Biotransformation by the liver: Oxidation, Glucuronidation 8. Takes 12-16 hours before effect is observed

35. Vitamin K Synthesis of Functional Coagulation Factors VII IX X II Vitamin K-Dependent Clotting Factors

36. Warfarin No Synthesis of Functional Coagulation Factors Antagonism of Vitamin K Warfarin Mechanism of Action Vitamin K VII IX X II

37. Mechanism of Action Coumarins block the Gamma Carboxylation of glutamic acid residues of Clotting factors II,VII, IX, X as well as the endogenous anti- coagulants C & S. Coumarins block the Gamma Carboxylation of glutamic acid residues of Clotting factors II,VII, IX, X as well as the endogenous anti- coagulants C & S. This is coupled with oxidative deactivation of Vitamin K This is coupled with oxidative deactivation of Vitamin K Coumarins and Indanediones inhibit the enzyme Vitamin K epoxide reductase that converts Vitamin K epoxide back into the active hydroquinone (reduced form) Coumarins and Indanediones inhibit the enzyme Vitamin K epoxide reductase that converts Vitamin K epoxide back into the active hydroquinone (reduced form) Thus they prevent the activation of Vitamin K and hence along with it carboxylations of clotting factor residues Thus they prevent the activation of Vitamin K and hence along with it carboxylations of clotting factor residues

38. Why Carboxylation is necessary? Carboxylation is necessary for ability of clotting factors to bind Ca and to get bound to phospholipid surfaces which is necessary Carboxylation is necessary for ability of clotting factors to bind Ca and to get bound to phospholipid surfaces which is necessary for coagulation for coagulation Factor VII affected first, then IX, X, and finally Factor II (depends upon half lives of circulating factors) Factor VII affected first, then IX, X, and finally Factor II (depends upon half lives of circulating factors)

41. Uses Same as Heparin and other Anticoagulants Same as Heparin and other Anticoagulants Monitoring necessary because of its low therapeutic index Monitoring necessary because of its low therapeutic index PT (Prothrombin time is noted; time taken for blood to clot) PT (Prothrombin time is noted; time taken for blood to clot) Patients on Heparin are shifted to oral warfarin after 3-5 days Patients on Heparin are shifted to oral warfarin after 3-5 days

42. Adverse Effects 1. Bleeding Most common and most serious adverse effect; Epistaxis, hematuria, GIT Bleeding, internal hemorrhages Epistaxis, hematuria, GIT Bleeding, internal hemorrhages 2. Cutaneous Necrosis This is due to decreased activity of Protein C This is due to decreased activity of Protein C Protein C and Protein S found in bone & other tissues also require Gamma carboxylations Protein C and Protein S found in bone & other tissues also require Gamma carboxylations 3. Infarction of breast, fatty tissues, intestine and extremities due to venous thrombosis caused by again decreased activity of Protein C

44. Antidote of Warfarin Stop Warfarin Stop Warfarin Give Vitamin K (Antidote) Give Vitamin K (Antidote) Also Fresh frozen plasma, Prothrombin complex concentrates and Recombinant factor VIIa can be administered Also Fresh frozen plasma, Prothrombin complex concentrates and Recombinant factor VIIa can be administered

45. Contraindications 1. Pregnancy Fetal protein in bone and blood affected Fetal protein in bone and blood affected -Causes birth defects including abnormal bone formation, bone hyperplasia -CNS Defects, fetal hemorrhage, fetal hypoprothrombinemia and fetal death may occur 2. Other contraindications same as heparin

46. Drug Interactions of Warfarin A.Pharmacokinetic Interactions 1. Agents that inhibit metabolism of warfarin Cimetidine Cimetidine Imipramine Imipramine Cotrimoxazole Cotrimoxazole Chloramphenicol Chloramphenicol Ciprofloxacin Ciprofloxacin Metronidazole Metronidazole Amiodarone Amiodarone

47. 2. Drugs that increase metabolism of Warfarin Barbiturates Barbiturates Rifampin Rifampin 3. Drugs that displace warfarin from binding sites on plasma albumin Chloral hydrate Chloral hydrate NSAIDs NSAIDs 4. Drugs that decrease GIT absorption of warfarin Cholestyramine Cholestyramine

48. B. Pharmacodynamic Interactions 1. Synergistic effect Heparin Heparin Aspirin Aspirin Antibiotics: Decrease bacterial flora—decrease Vitamin K synthesis— increased warfarin effect Antibiotics: Decrease bacterial flora—decrease Vitamin K synthesis— increased warfarin effect

49. Physiological/Pathological Factors affecting Warfarin Action 1. Increased warfarin action Malnutrition, debility (Decreased Vit. K) Malnutrition, debility (Decreased Vit. K) Liver disease, chronic alcoholism (Decreased clotting factors) Liver disease, chronic alcoholism (Decreased clotting factors) Hyperthyroidism (Increased degradation of Clotting factors) Hyperthyroidism (Increased degradation of Clotting factors) Newborns (Decreased vitamin K) Newborns (Decreased vitamin K)

50. 2. Decreased Warfarin Action Pregnancy (Increased clotting factors) Pregnancy (Increased clotting factors) Nephrotic syndrome Nephrotic syndrome Warfarin resistance (Genetic) Warfarin resistance (Genetic)

51. CharacterHEPARINWARFARIN Route of Administration ParenteralOral Polarity Polar charged molecule Uncharged Onset of Action Rapid 12-16 Hours Mechanism of Action Accelerates inactivation of clotting factors by Antithrombin III Inhibits gamma Carboxylation of glutamic acid residues of clotting factors

52. Therapeutic Index Not low; safe Low; not safe MonitoringaPTTPT Adverse Effect Differences Thrombocytopenia,,Oste oporosis, alopecia, anaphylaxis Cutaneous Necrosis, Infarction of breast, fatty and other tissues Management of Patient Start with Heparin Switch over to warfarin in 3-5 days Antidote Protamine Sulfate Vitamin K ContraindicationNotPregnancy Interactions Not significant Significant