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Blood Vessel Injury IX IXa XI XIa X Xa XII XIIa Tissue Injury Tissue Factor Thromboplastin VIIa VII X Prothrombin Thrombin Fibrinogen Fribrin monomer Fibrin polymer XIII Intrinsic PathwayExtrinsic Pathway Factors affected By Heparin Vit. K dependent Factors Affected by Oral Anticoagulants
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Prevent coagulation Dissolve clots Prevent bleeding and hemorrhage - Hemostatic Overcome clotting deficiencies (replacement therapies)
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A. Reduce the formation of fibrin clots. 1. INDIRECT THROMBIN INHIBITORS UFH: Heparin LMWH: Enoxaparin, dalteparin, tinzaparin SYNTHETIC: Fondaparinux 2. DIRECT THROMBIN INHIBITORS Parenteral: Hirudin, lepirudin Oral: Ximelagatran, dabigatran 3. ORAL ANTICOAGULANT DRUGS Coumarin anticoagulants warfarin – dicumarol
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B. Lyse thrombi already formed Streptokinase, Urokinase, Anistreplase Tissue Plasminogen Activator: Alteplase, Reteplase, Tenecteplase C. Antiplatelet drugs Aspirin, clopidogrel, ticlopidine Platelet glycoprotein IIa/IIIb Receptor blockers Others: dipyridamole, cilostazol
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INR Ratio of PT of patient PT of normal person plasma INR = (patient PT/mean normal PT) ISI ISI= International sensitivity Index Relate measured prothrombin time to WHO reference standard thromboplastin ISI = 1
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Life saving drugs Enhance degradation of clots Activation of endogenous protease Plasminogen (inactive form) is converted to Plasmin (active form) Plasmin breaks down fibrin clots Recently formed thrombus is easily lysed by these drugs. Aged thrombi (72 hrs) are usually resistant.
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Exogenously administered drugs Streptokinase - synthesized by streptococci convert plasminogen to plasmin Urokinase - human enzyme synthesized by kidney convert plasminogen to plasmin no immune response Plasmin is formed inside a thrombus, is protected from plasma antiplasmins, which allow it lyse the thrombus from within
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Alteplase : Tissue plasminogen activator (tPA) - genetically cloned no immune reaction EXPENSIVE Activate plasminogen bound to fibrin Tenectreplase mutant form of t PA has longer half life Anistreplase (APSAC) Purified human plasminogen and bacterial streptokinase
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Pulmonary embolism with hemodynamic instability Severe deep venous thrombosis Ascending thromboplebitis Acute myocardial infarction (streptokinase loading dose 250,000 units) Acute ischemic stroke (Recombinant t PA)
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Bleeding: Fibrinolytic drugs may lyse both normal and pathologic thrombi. Less effect is seen with t-PA (selectively activates plasminogen that is bound to fibrin) than streptokinase. Bleeding can be controlled by Aminocaproic acid (inhibits plasminogen activation) Hypersensitivity reaction: streptokinase Arrhythmias: Bradycardia, tachycardia Free radicals generated after fibrinolysis.
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Absolute Prior intracranial hemorrhage Known structural cerebral vascular lesion Known malignant intracranial neoplasm Ischemic stroke within 3 months Suspected aortic dissection Active bleeding or bleeding diathesis
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Relative Uncontrolled hypertension Major surgery within 3 weeks Recent internal bleeding For streptokinase prior allergic reaction Pregnancy Active peptic ulcer Current use of warfarin
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Drugs which inhibit plasminogen activation and dissolution of clot 1- Epsilon amino-caproic acid (EACA) 2- Tranexaemic acid Indications Overdose of streptokinase To prevent recurrence of subarachnoid and G.I hemorhage Abruptio placentae, PPH and menorhagia
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THROMBOXANE A 2 INHIBITORS Aspirin ADP RECEPTOR INHIBITORS Ticlopidine Clopidogrel Prasugrel GLYCOPROTEIN IIB/IIA INHIBITORS Abciximab Eptifibatide PHOSPHODIESTERASE INHIBITORS Cilostazol
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GP Ia GP IIb/IIIa Fibrinogen GP IIb/IIIa Platelet.. …......... … … … … … … Granules TXA 2 ADP 5-HT Aspirin Clopidogrel Ticlopidine Abciximab GP Ib Collagen Vascular Endothelium vWF
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Mechanism & Pharmacological effects Aspirin and most other NSAIDs inhibit the synthesis of prostaglandins: Decrease endothelial synthesis of PGI 2 (prostacyclin) Decrease thromoboxane A 2 production in platelets by inhibiting cyclooxygenase type I and type 2 Irreversible inhibition of cyclooxygenase and platelet aggregation for the life of the platelet It may cause bleeding, especially in the GI, and hypoprothrombinemic effect (high doses)
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Dose of aspirin 75-325 mg Prophylactic for transient cerebral ischemia Reduce the incidence of recurrent MI Decrease mortality in postmyocardial infarction patients
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Mechanisms and Pharmacological effects: Inhibits adenosine diphosphate (ADP)- induced expression of platelet glycoprotein receptors & reduces fibrinogen binding and platelet aggregation. Can be used in patients who are unresponsive to aspirin to prevent thrombotic stroke.
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Prevent thrombosis in patients undergoing placement of a coronary stent Ticlopidine Prevention of stroke in patients with a history of transient ischemic attack (TIA) or thrombotic stroke Adverse effects: Nausea, dyspepsia and diarrhea, thrombotic thrombocytopenic purpura
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Unstable angina or non-ST elevation acute myocardial infarction in combination with aspirin Neutropenia- Less with clopidogrel Clopidogrel is preferred over ticlopidine
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Chimeric (human-murine) monoclonal antibody binds to platelet glycoprotein IIb/IIIa receptors and prevents binding by fibrinogen used solely for the prevention of thrombosis in patients undergoing coronary angioplasty Parenteral administration
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Inhibits platelets adhesion to damaged blood vessels dosage increase in platelets cAMP formation and platelet Ca ++ which inhibits platelets aggregation Used in combination with aspirin to prevent cerebrovascular ischemia
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Vitamin K (oral and parenteral forms) K 1 and K 2 newborns, vit k deficiency in patients with poor diet, parenteral nutrition, recent surgery Plasma factors: factor VII, VIII, IX Desmopressin acetate (increase the factor VIII activity) Autoplex (factor VIII) Cryoprecipitate (plasma protein fraction) Used in DIC
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Fibrinolytic Inhibitors Aminocaproic acid Tranexamic acid
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Adjunctive therapy in hemophilia Control bleeding from fibrinolytic therapy Prophylaxis for bleeding from intracranial aneurysms Post-surgical GI bleeding Bladder hemorrhage secondary to radiation & drug-induced cystitis Gynecological bleeding – fibroids, PPH
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Calcium complexing agents sodium oxalate sodium edetate
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