Antiplatelets, Anticoagulants and Thrombolytics Flashcards
List five common thromboembolic diseases. (5)
DVT, PE, TIA, MI, stroke.
Explain the differences between a thrombus and an embolus. (2)
Thrombus: a clot adhered to a vessel wall.
Embolus: intraluminal clot that is distal to the site of origin.
Describe a venous thrombosis.
Causes (2)
Clot features. (3)
Treatments (2)
Associated with stasis of blood or abnormalities of the vessel wall.
Low platelet content, high fibrin content, called “red”.
Prescribe anticoagulants to prevent (warfarin or heparin).
Describe an arterial thrombosis.
Causes (1)
Clot features (3)
Treatments. (2)
Associated with atherosclerotic plaque rupture.
Platelet rich, but low fibrin, called “white”
Prescribe antiplatelet or fibrinolytic drugs.
Describe the effects of aspirin in low doses. (3)
Anticoagulent - irreversible COX-1 inhibition to inhibit thromboxane.
Explain why aspirin must be given in low doses to be an anticoagulent. (4)
Because at high doses, it inhibits COX-1 and COX-2, which blocks prostacyclin production, meaning it acts as an antipyretic and analgesic but can be pro-thrombotic.
Describe the pharmacokinetics of aspirin. (3)
t1/2 is 20 mins unless hydrolysed in the liver to salicylic acid which has a t1/2 of 3-12 hours.
Describe the ADRs of aspirin. (3)
Bleeding time is prolonged, increased risk of haemorrhagic stroke, peptic ulcer bleeding.
Explain why aspirin has to be stopped about a week before a surgery. (3)
Because aspirin inhibition of COX-1 is irreversible, so you have to wait until all of the platelets that have been inhibited have been destroyed. The lifespan of a platelet is about 7 days.
Describe 4 indications for aspirin therapy. (4)
Secondary prevention of stroke or TIA if other agents contraindicated.
Secondary prevention of acute conronary syndrome.
Post primary percutaneous coronary intervention or stent
Secondary prevention of MI in stable angina or peripheral vascular disease.
Describe the mechanism of action of P2Y_12 receptor antagonists (2)
Inhibit binding of ADP to P2Y_12 receptors. This inhibits the activation of GP IIb / IIIa receptors.
Name three P2Y_12 receptor antagonists. (3)
Give the common feature of the names of these drugs. (2)
Clopidogrel, prasugrel, ticagrelor.
Have -grel- in them, normally at the end but not always.
Describe the pharmacokinetics of clopidogrel. (3)
A prodrug with hepatic metabolism and a t1/2 of 7-8 hours.
Needs a loading dose for predictability of effect.
Describe the common indications for clopidogrel prescription. (4)
Reduces morbidity and mortality following an embolus stroke.
Reduces secondary events post MI (only prescribed for one year with aspirin)
Useful for prophylaxis in patients intolerant to aspirin.
Describe the pharmacokinetics of prasugrel. (3)
A prodrug with hepatic metabolism and a t1/2 of about 8 days.
Describe the pharmacokinetics of ticagrelor and explain why it is not commonly used. (3)
Given in active form and has active metabolites.
Very expensive.
Describe the MoA and effectiveness of GP IIb / IIIa inhibitors. (2)
Targets the final common pathway of complete aggregation. Results in an 80% reduction in aggregation.
Name three GP IIb / IIIa inhibitors and describe their mechanisms of action. (6)
Abciximab - monoclonal antibody irreversibly blocks GP IIb / IIIa to prevent fibrinogen binding.
Eptifibatide - synthetic peptide that binds irreversibly.
Tirofiban - reversible antagonist.
Describe the main ADR of GP IIb / IIIa inhibitors. (1)
Thrombocytopenia.
Name one phosphodiesterase inhibitor. (1)
Dipyridamole