10. Anti-platelets Agents

Question 1

What are the processes involved in homeostasis?

Answer 1

Vessel wall constriction
Platelet adhesion to sub-endothelial collagen, degranulation, aggregation, plug formation
Blood coagulation

Question 2

Define haemostasis

Answer 2

Arrest of haemorrhage

Question 3

Define thrombosis

Answer 3

Pathological formation of a “haemostatic” plug within the vasculature in the absence of bleeding

Question 4

What is virchows traid?

Answer 4

Three broad categories of factors that contribute to thrombosis

Stasis of blood flow
Endothelial injury
Hypercoagulbility

Question 5

What are the roles of anti platelet drugs?

Answer 5

Critical role for platelets in development of arterial thrombi
Damaged endothelium activates platelets which respond by adhering to endothelium and aggregating

Question 6

Examples of anti-platelet agents?

Answer 6

Cyclo-oxygenase inhibitors
ADP receptor pathway inhibitor
Phosphodiesterase inhibitors

Question 7

Mechanism of action of aspririn

Answer 7

XX0 check do we need to know this

Question 8

When is aspirin used for clinical indications?

Answer 8

Ischaemic stroke/ TIA 
Acute coronary syndrome 
Post Myocardial Infarcation
Following coronary bypass
Angina Pectoris 
Peripheral arterial disease/ claudication
Atrial fibrillation

Question 9

What are the adverse effects of aspirin?

Answer 9

Gastric irritation/bleeding
Hypersensitivity reactions
Reyes syndrome in children

Question 10

What are the drawbacks of aspirin?

Answer 10

Lack of response in some patients
-rare often related to poor drug adherence
Irreversible platelet
-continued bleeding risk for some time after stopping the drug

Question 11

What is the mechanism of action of clopidogrel?

Answer 11

XX

Question 12

What are the clinical indications of clopidogrel?

Answer 12

Secondary prevention in patients intolerant of aspririn
Used with aspirin for 3-12 months after acute coronary syndrome and after procedures to coronary arteries to prevent thrombosis

Question 13

What are the adverse effects of clopidogrel?

Answer 13

Gastro-intestinal irritation and bleeding
Dyspepsia
Hypersensitivity reactions

Question 14

What are the potential drawbacks of clopidogrel?

Answer 14

Pro-drug: delayed onset of action
Genetic variation of liver enzymes responsible for metabolism and activation so response varies between individuals
Drug-drug interactions
Irreversible inhibition of P2Y12 receptor

Question 15

What is prasugrel?

Answer 15

A prodrug but different chemical structure permits conversion to active metabolite in liver

An irreversible inhibitor of platelet P2Y12 receptor but greater absorption and higher metabolite bioavailibilty gives more predictable antiplatlet response than clopidogrel

Question 16

What is tricagrelor?

Answer 16

A pyrimidine that does not bind to ADP binding site but separate site on P2Y12 receptor to inhibit G-protein signalling
reversible inhibitor of platelet P2Y12 receptor with rapid onset and offset of action

Question 17

Dipyridamole-mechanism of action

Answer 17

XXX

Question 18

What are the clinical indications of Dipyridamole?

Answer 18

With oral anticaogulants for prevention of thromboembolism in patients with prosthetic heart valves

Given with aspirin for secondary prevention of ischaemic stroke (TIA)

Question 19

What are the adverse affects of dipyridamole?

Answer 19

Gastro-intestinal irritation/bleeding 
Dizziness, flushing and headache
Myalgia 
Chest pain 
Hypersensitivity reactions

Question 20

Abciximab –mechanism of action

Answer 20

XX

Question 21

What are the clinical indications of Abciximab?

Answer 21

Given with aspirin and heparin during coronary interventions in patients at high risk of MI

Question 22

What are the adverse effects of Abciximab?

Answer 22

Bleeding
Chest pain
Hypersensitivity