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Anticoagulants_Classroom_Presentation.pptx

This is the presentation prepared to explain anticoagulants in easy and simple language.

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ANTICOAGULANTS Drugs that prevent harmful blood-clot formation Pharmacology • Third Year B.Pharm Focus of the session Mechanism • Classification • Uses • Adverse effects • Monitoring • Antidotes 1
Start with a clinical problem Why do we need anticoagulants? Pharmacology • Anticoagulants CLINICAL CASE A patient develops pain, swelling and warmth in one leg after prolonged immobilisation. What could happen if the clot breaks and reaches the lungs? DVT Pulmonary → embolism Learning outcomes • Define anticoagulants and state their role • Identify the main drug classes • Explain heparin and warfarin mechanisms • Compare monitoring and antidotes • Select the appropriate drug in common situations 2
What are anticoagulants? Core definition Pharmacology • Anticoagulants Anticoagulants are drugs that: • Prevent formation of new blood clots • Prevent an existing clot from becoming larger • Reduce the risk of clot-related complications They do not directly dissolve an already formed clot. Simple picture Without treatment Anticoagulation reduces further clotting 3
Do not confuse these three groups A common examination point Pharmacology • Anticoagulants Antiplatelets Act mainly on platelets Useful mainly in arterial thrombosis Examples: aspirin, clopidogrel Anticoagulants Act mainly on coagulation factors Prevent formation or extension of clots Examples: heparin, warfarin Fibrinolytics Activate clot breakdown Can dissolve a recently formed clot Examples: alteplase, streptokinase 4
The clotting pathway in one minute Only the essential steps Pharmacology • Anticoagulants Factor Xa Key enzyme Prothrombin Factor II Thrombin Factor IIa Fibrinogen Soluble protein Fibrin clot Stable mesh converts converts converts forms Most important drug targets Factor Xa and Thrombin (IIa) Blocking either step decreases fibrin formation and reduces clotting. 5
Classification of anticoagulants Organised by route and mechanism Pharmacology • Anticoagulants ANTICOAGULANTS Parenteral • Unfractionated heparin • LMWH • Fondaparinux • Argatroban / bivalirudin Oral • Warfarin • Dabigatran • Rivaroxaban • Apixaban / edoxaban In vitro • Sodium citrate • Oxalate • EDTA • Heparin in sample tubes 6
Heparin: mechanism of action Rapid parenteral anticoagulant Pharmacology • Anticoagulants 1 Heparin enters blood Given intravenously or subcutaneously. 2 Binds Antithrombin III Heparin makes the natural inhibitor much more active. 3 Clotting factors are inhibited Mainly thrombin (IIa) and Factor Xa. HEPARIN Antithrombin III blocks Factor Xa + Thrombin IIa Result: less thrombin, less fibrin and less clot extension 7
Heparin: clinical profile Uses, monitoring, adverse effects and antidote Pharmacology • Anticoagulants Uses • DVT and pulmonary embolism • Acute coronary syndromes • Haemodialysis and cardiac procedures Monitoring • Unfractionated heparin: aPTT • Platelet count is monitored • LMWH usually needs no routine aPTT Adverse effects • Bleeding • Heparin-induced thrombocytopenia • Osteoporosis with prolonged use Antidote • Protamine sulfate • Neutralises heparin • Dose is based on amount of heparin given 8
Low-molecular-weight heparins (LMWH) Smaller heparin fragments with predictable action Pharmacology • Anticoagulants EXAMPLES Enoxaparin Dalteparin Nadroparin Usually administered by subcutaneous injection Mechanism LMWH activates Antithrombin III and inhibits Factor Xa more strongly than thrombin. Main target: Factor Xa Why is LMWH convenient? • Better subcutaneous absorption • Longer duration of action • More predictable response • Less laboratory monitoring 9
Other parenteral anticoagulants Fondaparinux and direct thrombin inhibitors Pharmacology • Anticoagulants FONDAPARINUX Synthetic drug 1 Antithrombin III Binds and activates AT-III. 2 Selective Factor Xa inhibition Reduces thrombin formation. Useful in prevention and treatment of venous thromboembolism DIRECT THROMBIN INHIBITORS Examples Argatroban • Bivalirudin • Lepirudin Thrombin IIa Directly block thrombin less → fibrin formation May be used when heparin cannot be used, such as selected patients with HIT. 10
Warfarin: mechanism of action Oral vitamin K antagonist Pharmacology • Anticoagulants Vitamin K VKOR recycles vitamin K Liver makes functional clotting factors II • VII • IX • X WARFARIN blocks VKOR Result: reduced synthesis of vitamin K-dependent factors Memory: 1972 = X, IX, VII, II 11
Warfarin: practical points Slow onset, careful monitoring Pharmacology • Anticoagulants Route & onset Oral drug Slow onset of action Used mainly for long-term therapy Monitoring Prothrombin time (PT) Reported as INR Dose is individualised Antidote Vitamin K Severe bleeding may need additional reversal measures Important adverse effects and precautions • Bleeding is the major adverse effect • May cause skin necrosis early in therapy • Many drug and food interactions • Generally avoided during pregnancy 12
Direct oral anticoagulants (DOACs) Fast, predictable oral anticoagulation Pharmacology • Anticoagulants DIRECT THROMBIN INHIBITOR DABIGATRAN Thrombin IIa ↓ Fibrin formation Specific reversal agent: idarucizumab DIRECT FACTOR Xa INHIBITORS RIVAROXABAN APIXABAN EDOXABAN “XABAN” drugs block Factor Xa Specific reversal agent may be used for selected Xa inhibitors where available. 13
Heparin versus warfarin High-yield comparison Pharmacology • Anticoagulants Feature Heparin Warfarin Route IV / SC Oral Onset Rapid Slow Mechanism Activates Antithrombin III Blocks vitamin K recycling Main effect Inhibits Xa and IIa Reduces II, VII, IX and X Monitoring aPTT PT / INR Antidote Protamine sulfate Vitamin K Pregnancy Commonly preferred when needed Generally avoided Feature Heparin Warfarin 14
Monitoring and reversal: remember the pairs Rapid recall Pharmacology • Anticoagulants Unfractionated heparin MONITOR aPTT REVERSAL Protamine sulfate Warfarin MONITOR PT / INR REVERSAL Vitamin K Dabigatran MONITOR No routine test REVERSAL Idarucizumab 15
Clinical application: choose the drug Think before answering Pharmacology • Anticoagulants CASE A patient with acute pulmonary embolism requires immediate anticoagulation. Which characteristic is most important? Reasoning 1 Need rapid action An emergency requires an anticoagulant with immediate or rapid onset. 2 Choose a parenteral drug Heparin or an appropriate LMWH may be selected depending on the patient. 3 Plan continuation Long-term oral therapy may follow after clinical assessment. Key answer: rapid onset is the deciding feature. 16
One-slide memory map Revise the whole topic Pharmacology • Anticoagulants Heparin AT-III Xa + IIa → LMWH AT-III mainly Xa → Fondaparinux AT-III selective Xa → Direct thrombin inhibitors Directly block IIa Warfarin ↓ Vitamin K factors 1972 Dabigatran Direct thrombin inhibitor Xabans Direct Factor Xa inhibitors Heparin aPTT Protamine → → Warfarin PT/INR Vitamin K → → 17
Summary and quick viva End-of-session check Pharmacology • Anticoagulants Take-home points • Anticoagulants prevent new clot formation and clot extension • Factor Xa and thrombin are the main targets • Heparin acts rapidly through Antithrombin III • Warfarin reduces vitamin K-dependent factors • Bleeding is the major adverse effect of all anticoagulants Quick viva questions 1 What is the antidote of heparin? 2 Which test monitors warfarin? 3 Name one LMWH. 4 Which factors depend on vitamin K? 5 What does a “xaban” drug inhibit? THANK YOU 18