Pharmacology of Anticoagulants + Antiplatelets Flashcards
What are the 3 drugs?
Anticoagulants
Antiplatelets
Fibrinolytic agents
What are examples of anticoagulants?
Factor Xa inhibitors
Antithrombins
Heparin + Vit K antagonists
What do anticoagulants do?
Modify clotting mechanisms
What is an example of an antiplatelet?
Aspirin
What do antiplatelets do?
Inhibit Cox-1 activity
= inhibit platelet aggregation
What is an example of a fibrinolytic agent?
Alteplase
What do fibrinolytic agents do?
Break down fibrin
What are the classes of anticoagulants?
Factor Xa inhibitors
Direct thrombin inhibitors
Heparin + LMW heparins
Vitamin K antagonists
What is an example of a factor Xa inhibitor?
Apixaban
What a direct thrombin inhibitor?
Dabigatran
What is an example of a vitamin K antagonist?
Warfarin
What is the 1st choice treatment for DVT or PE?
Apixaban
Rivaroxaban
What can be used to treat DVT if apixaban + rivaroxaban are contraindicated?
1st
LWMH
Followed by dabigatran etexilate or edoxaban
What can be used to treat DVT if apixaban + rivaroxaban are contraindicated?
2nd
LMWH with vitamin K antagonist for 5 days
Followed by vitamin K antagonist on its own
What does a DVT look like?
Swollen red inflamed leg
How does DVT happen?
Big blood clot prevents venous drainage from leg
BUT still get arteriole flow = oedema
What are the DOACs?
Apixaban
Rivaroxaban
Dabigatran
Edoxaban
What is the mechanism of action for dabigatran?
Reversible inhibitor of free thrombin
What is the mechanism of action for apixaban, edoxaban + rivaroxaban?
Reversible inhibitor of factor Xa
What is the indication of ALL DOACs?
Prevention of stroke + systemic embolism in patients with non-vascular AF
Secondary prevention DVT
What is the indication for ALL DOACs except for edoxaban?
Prevention of venous thromboembolism following elective hip or knee replacement surgery
What is the indication for rivaroxaban?
Prevention of atherothrombotic events
What are the contra-indications of apixaban?
Risk of significant bleeding
Which conditions can cause a risk of significant bleeding with apixaban?
GI ulceration
Malignant neoplasms
Oesophageal varices
What is the STOPP criteria for apixaban?
Elderly
= risk of bleeding
eg. severe hypertension
What are the side effects of apixaban?
Anaemia
Haemorrhage
How does heparin inhibit coagulation?
Activating antithrombin III (AT III)
What are examples of LMWH?
Dalteparin sodium
Enoxaparin sodium
Tinzaparin sodium
What do LMWH do?
Inactivate factor Xa + thrombin
What do both heparin + LMWH have?
Immediate onset of action
What is the problem with LMWH + heparin?
Inactive if given orally
= must be administered IV or SC (for LMWH)
What is the half life of heparin + what does this mean?
SHORT
= must be given frequently, continuously
What is good about LMWH compared to heparin?
Longer duration of action
= allows once daily dosing
How are heparins + LMWH eliminated?
Renally
= need to be careful with patients with low kidney function
How are heparins + LMWH eliminated?
Renally
= need to be careful with patients with low kidney function
What are the side effects of heparin + LMWH?
Bleeding
Hypersensitivity
How is the overdose of heparin + LMWH treated?
IV protamine
What is an example of a vitamin K antagonist?
Warfarin
How does Warfarin work?
Inhibitors Vitamin K1 dependent clotting factors
= II, VII, IX + X
What is problem with Warfarin?
At least 2-3 days for anticoagulant effects to develop
What are the side effects of Warfarin?
Haemorrhage
Skin necrosis
What is the advantage of Warfarin?
Can be given orally
What does Warfarin block?
Vitamin K reductase
How does aspirin work?
Inhibits COX-1
= inhibits the synthesis of TXA2
Aspirin further explained
Platelets do not contain DNA or RNA
= cannot synthesise new COX-1
= inhibition irreversible
What is the clinical use of aspirin?
Use prophylactically to prevent arteriole thrombosis which lead to…
TIA
Stroke
MI
What is Ticlopidine + Clopidogrel?
Antiplatelets
What is Ticlopidine + Clopidogrel given for?
MI
= blocks effect of ADP