Antiplatelet And Antifibrinolytics

Question 1

Use of antiplatelets in arterial or venous thrombosis?

Answer 1

Arterial.

Forms at site of atherosclerosis following plaque rupture
Lower fibrin content, high platelet content

Question 2

How long is a platelets lifespan?

Answer 2

8-10 days

Question 3

How does prostacyclin prevent platelet aggregation?

Answer 3

PGI2 prostacyclin produced and released by endothelial cells

PGI2 binds to platelet receptors
Increases camp
Increased camp Causes less calcium reflux
Prevents platelet aggregation

Question 4

Chemical changes leading to platelet aggregation

Answer 4

Release of platelet granules - ADP, thrombin
Initiates activation
Increase calcium efflux and decrease camp in platelets
Amplification

Question 5

Aspirin mechanism

Answer 5

Inihibits COX1 mediated production of TXA2 (thromboxane A2)

Reduces platelet aggregation
Irreversible

Question 6

Why does aspirin not completely inhibit all platelet aggregation?

Answer 6

Many other pathways to produce TXA2

Question 7

Aspirin ADRS

Answer 7

GI bleeding - causes PUD
Brain haemorrhage

Question 8

Aspirin contras and DDIs

Answer 8

Can cause Reye’s syndrome - avoid under 16yrs!!!
Hypersensitivity reactions
Do not give in 3rd trimester - premature closure ductus arteriosus

Do not give with other antiplatlet/anticoag

Question 9

Why does the antiplatelets effect of aspirin last the entire lifespan of a platelet?

Answer 9

Platelets are non nucleatedso can’t generate more TXA2 in their lifetime.

Question 10

Aspirin indications

Answer 10

AF
Secondary prevention of ACS, stroke, TIA
MI 300mg loading dose

Question 11

Clopidogrel, ticagrelor drug class and mechanism?

Answer 11

ADP receptor antagonists
Inhibit binding of ADP to P2Y12 receptor
Inhibits ADP platelet aggregation

Clop- irreversible
Ticagrelor-reversible

Question 12

Compare clopidogrel vs ticagrelor/prasugrel onset of action times

Answer 12

Clopidogrel has slow onset
Ticagrelor and prasugrel have more rapid onset

Question 13

ADP receptor antagonist ADRS

Answer 13

Bleeding
GI upset
Rarely thrombocytopenia

Question 14

ADP receptor antagonist contras and DDIs

Answer 14

Caution in high bleed risk patients/renal hepatic impairment

Do not give with CYP inhibitors (increase plasma conc) - omeprazole!! Use other PPIs with Clopidogrel

Needs to be stopped 7 days before surgery - bleeding risk

Question 15

ADP receptor antagonist indications

Answer 15

Ischaemic stroke
NSTEMI

Clopidogrel long term mono therapy when aspirin is contraindicated

Question 16

Dipyridamole (phosphodiesterase inhibitor) mechanism

Answer 16

Dipyridamole inhibits cellular reuptake of adenosine
Increased conc of adenosine
Inhibits platelet aggregation
Via A2 receptors

Question 17

Dipyridamole indications

Answer 17

Secondary prevention of ischameic stroke/TIA

Question 18

Dipyridamole ADRS and DDIs

Answer 18

Vomiting and diarrhoea
Dizziness

Do not give with other antiplatelet/anticoag agents
Do not give with adenosine!! (Antiarrythmic, for SVT)

Question 19

Abciximab class

Answer 19

Glycoprotein 2b/3a inhibitor

Question 20

Abciximab mechanism

Answer 20

Antibody
Blocks 2b/3a receptors

Blocks binding of fibrinogen and VWF
Targets final common pathway!! Complete platelet aggregation inhibition