Anti-platelet drugs Flashcards
(21 cards)
What happens in primary clotting?
- Platelet aggregation
- Thromboxane and ADP release by platelets
- Aggregation together and damaged part of endothelium
What occurs in secondary clotting?
- Coagulation
- Thrombin stimulates platelet aggregation and forms fibrin polymer
- Fibrin mesh forms around clot
What substances activate aggregation?
- Von-Willebrand factor and collagen (sub endothelial proteins)
- Thrombin
- ADP from activated platelet
- Thromboxane made by COX-1
What substances aggregation inhibited by?
- Nitric oxide
- Prostacyclin
What different anti-platelet drugs are there?
- Aspirin
- Clopidogrel
- Abeiximab
- Tirofiban
What does aspirin do?
- Inhibits COX-1 so no thromboxane
What does clopidogrel do?
- Blocks P2Y12 receptor also slows down chain reaction
What do abeiximab and tirofiban do?
- Target glycoprotein gpIIb/ IIIa
What does COX-1 do?
- Constitutive functions
- Inhibited- gastric bleeding
What does COX-2 do?
- Inflammation and pain
- Inhibited- analgesia, anti-inflammatory effect
How does aspirin work?
- High doses of aspirin and NSAIDs inhibit COX-1 and COX-2
- Therefore prostanoid synthesis
Describe aspirin prescription in anti-platelet function
- Low dose
- Irreversibly acetylates COX-1 in platelets and endothelium
- Only endothelium can regenerate COX-1 enzyme due to nucleus to presence
What are the clinical uses of low-dose aspirin?
- COX-1 inhibitor
- Low-dose front-line anti-platelet
- Prevention of MI
- Prophylaxis
- Thrombolysis after MI
Describe the function of clopidogrel
- Pro-drug converted to active metabolite CP450 in liver
- Non-competitive, irreversible antagonist of platelet ADP receptors
- Reduces gpIIb/IIa reduceing aggregation
What are the clinical uses of clopidogrel?
- Prevention of MI/ stroke
- Patients intolerant to low-dose aspirin
- After MI or intracoronary stent
What are the side effects of clopidogrel?
- Severe neutropenia
- GI bleeds
What are abciximab and tirofiban?
- gp IIb/IIIa antagonists
- Relatively new drugs
- IV
- SE includes haemorrhage
Describe the mechanism of thrombolysis
- Plasmin enzyme targets fibrin and breaks it down into soluble degradation products
Give examples of plasminogen activators
- Streptokinase
- Anistreplase
- Urokinase
- Rt-PA
How do you manage acute MI?
- Reduction in anginal pain (oxygen, GTN)
- Initiate reperfusion (anti-platelet, thrombolytic, heparin)
- Protect myocardium ( β blocker, ACE inhibitor)
- Secondary prevention (aspirin, lipid-lowering lifestyle)
What are additional approaches to clots?
- Delivery of thrombolytics by arterial catheter (faster response)
- Drug eluting stents
