Antiplatelet Drugs Flashcards

1
Q

How do platelets adhere to collagen?

A

GP1b receptors and vWF

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2
Q

What do platelets release upon initial activation and what receptors do they bind to?

A

ADP - P2Y12 receptor

Thromboxane A2 - TP receptor

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3
Q

Activation of what receptor on platelets results in platelet aggregation and thrombus formation?

A

GPIIb/IIIa

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4
Q

What is the mechanism of action of aspirin?

A

Acetylates serine –> inactivates cyclooxygenase (COX)

–> decreased prostglandin synthesis –> decreased thromboxane A2 –> less platelet aggregation

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5
Q

What are indications for aspirin?

A

Reduced mortality in acute MI and to prevent future MI
Reduced stroke risk
Maintain graft patency in CABG or stent placement

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6
Q

What are limitations of aspirin therapy?

A

Allergy
GI intolerance
Aspirin resistance

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7
Q

What are oral antiplatelet therapies?

A
Aspirin
Clopidogrel
Prasugrel
Ticagrelor
Cilostazol
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8
Q

What drugs are in the category of thienopyridines?

A

Ticlopidine (no longer used)
Clopidogrel
Prasugrel
Ticagrelor

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9
Q

What is the mechanism of action of dipyridamole?

A

Inhibits platelet cAMP phosphodiesterase –> increased cAMP –> inhibit platelet aggregation

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10
Q

What is the mechanism of action of thienopyridines?

A

Inhibit ADP receptor P2Y12 –> inhibit activation of GPIIb/IIa –> inhibit fibrinogen binding

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11
Q

Describe the metabolism of Clopidogrel and relative importance of CYP system in the metabolism

A

Clopidogrel is a prodrug
Undergoes CYP-dependent oxidation twice to be fulling activated (CYP2C19 and CYP3A4)
Any polymorphism is CYP enzymes can have significant effects active metabolism of drug –> excess clopidogrel

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12
Q

Describe the metabolism of Prasugrel and relative importance of CYP system in the metabolism

A

Prasugrel is a prodrug
Only undergoes CYP-dependent oxidation once
CYP2C19 plays a smaller role in the oxidation
CYP system not as important as in clopidogrel

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13
Q

Describe the metabolism of Ticagrelor and relative importance of CYP system in the metabolism

A

Ticagrelor is not a prodrug
Acts directly on P2Y12 ADP receptor as soon as its ingested
CYP system plays no role for ticagrelor

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14
Q

What are indications for clopidogrel?

A

Acute coronary syndrome (reduced MI, stroke death in patients with recent MI, stroke)
Reduced risk of in-stent thrombosis

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15
Q

Do PPIs cause diminished antiplatelet activity of clopidogrel?

A

No

Just increased risk of GI bleeds if on PPIs and not put on PPIs

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16
Q

How does Prasugrel compare to Clopidogrel?

A

Better anti-platelet effect with Prasugrel, decreased CV death/MI events
However, also have slight increase in major bleeding events

17
Q

Which groups of patients should not use Prasugrel?

A

Prior stroke
Age >75
Low body weight

18
Q

What are the GPIIb/IIIa receptor antagonists?

A

Abciximab, eptifibatide, tirofiban

19
Q

What is the mechanism of action of GPIIb/IIIa receptor antagonists?

A

Inhibit GPIIb/IIIa receptors –> prevent platelet aggregation

20
Q

Why are GPIIb/IIIa receptor antagonists not used often?

A

Must be given IV

Hence only really used in cath lab now, despite being most potent platelet inhibitors

21
Q

When is abciximab used?

A

Primary angioplasty in patients with STEMI

22
Q

When is eptifibatide used?

A

Used in unstable angina/NSTEMI

23
Q

When are GPIIb/IIIa receptor antagonists being used now?

A

Patients with unstable angina/NSTEMI undergoing PCI and already receiving antiplatelet, anticoagulant , antiischemic agents