Antiplatelets and Anticoagulants Flashcards
How is arterial thrombosis managed?
Anti-platelets
How is venous thrombosis managed?
Anti-coagulants
What is the mechanism of action of aspirin?
Inhibits cyclo-oxygenase which is necessary to produce thromboxane A2
What are some of the possible side effects of aspirin?
Bleeding
Bronchospasm
What is the mechanism of action of clopidogrel and prasugrel? (anti-platelets)
ADP receptor antagonists
What is the mechanism of action of dipyridamole? (anti-platelet)
Phosphodiesterase inhibitor which reduces the production of cAMP which is a second messenger in platelet activation
What is the mechanism of action of abciximab? (anti-platelet)
GP IIb/ IIIa inhibitor which inhibits aggregation
How long before surgery should anti-platelets be stopped?
7 days prior to surgery
This is because anti-platelets affect platelet function for their life span which is 7 days long
Which drug is first line for acute thrombosis?
Heparin
*Has an immediate effect
How long is heparin given for after an acute incident?
6 months
Then switch to oral anticoagulants to avoid lifelong injections
What are the two forms of heparin?
Unfractioned
LMWH
How are the different forms of heparin monitored?
APTT - unfractioned
Anti-Xa assay - LMWH
What are some of the possible complications of heparin?
Bleeding
Heparin induced thrombocytopenia (HITT)
Osteoporosis (when used long-term)
How is heparin reversal achieved?
Stop the heparin
Protamine sulphate (if bleeding is severe) - this binds to and turns off heparin
Give some examples of coumarin anticoagulants
Warfarin
Phenindione
Acenocoumarin
Phenprocoumon
What is the mechanism of action of the coumarin anticoagulants?
Inhibition of vitamin K
What is the mechanism of action of vitamin K?
Carboxylation of clotting factors
What factors are vitamin K dependent?
Factors II, VII, IX and X
Protein C and S
What is the mechanism of action of warfarin?
Blocks the ability of vitamin K to carboxylate clotting factors
How is warfarin therapy monitored?
INR
What are some of the possible complications of warfarin therapy?
BLEEDING:
Skin bruising
Epistaxis
GI bleeds
Intracerebral bleeds
How is warfarin reversal achieved?
Omit warfarin dose
Administer oral vitamin K
Administer clotting factors (FFP or factor concentrates)
What are the indications for use of the new anticoagulants?
Used instead of LMWH as prophylaxis in elective hip and knee replacement surgery
Used for selected patients for stroke prevention in AF
Used for treatment of DVT/ PE
What is the mechanism of action of dabigatran?
Directly inhibits thrombin
What is the mechanism of action of rivaroxaban and apixaban?
Xa inhibitors
Xaban = Xa inhibitors
