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Exam 4 Antiplatelets PHRM 844 > Antiplatelets > Flashcards

Antiplatelets Flashcards

1
Q

What is the role that platelets play in hemostasis?

A
  1. Adhere to regions of injured blood vessel and are activated (shape change)
  2. recruit to injured site
  3. form a hemostatic plug
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2
Q

What are the three phases of platelet activation?

A
  1. adhesion
  2. secretion
  3. aggregation
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3
Q

What is the role of GPIa/GPIb receptors in platelet activation?

A

GP1a –> binds to collagen
GP1b –> binds to von willebrand factor bridged to collagen

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4
Q

What three molecules are secreted by platelets?

A

ADP
5-HT
TXA2

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5
Q

what are the molecules secreted by platelets role in hemostasis?

A

ADP, 5HT, TXA2 –> activate and recruit other platelets
TXA2 & 5HT –> potent vasoconstrictors

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6
Q

Explain the role of fibrinogen and GP IIb/IIIa receptors in platelet function?

A
  • Factors activation induces conformation of G2b/3a receptors to bind fibrinogen
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7
Q

Explain the role of aspirin as an antiplatelet drug and why it has a preferential effect on platelets over the endothelium.

A
  1. inhibition of TXA2 synthesis in platelets due to cox-1 inhibition
  2. irreversible
  3. PGI2 production inhibited by higher doses
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8
Q

What are the indications for aspirin and its SEs?

A
  1. prophylaxis and tx of arterial thromboembolic disorders
    upper GI bleeding due to inhibition of COX-1
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9
Q

what is the mechanism of clopidogrel and its clinical properties?

A

P2Y12 ADP receptor on platelet surface
– thienopyridine class of ADP receptor inhibitors (pro-drug)
– irreversibly block ADP on platelet and subsequent activation of Gp2b/3A complex

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10
Q

what is the mechanism of prasugrel and its clinical properties?

A

P2Y12 ADP receptor on platelet surface
- prodrug that requires esterases + CYP 3A4/2B6
- high risk of bleeding, not recommended in elderly or before CABG

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11
Q

what is the mechanism of ticagrelor and its clinical properties?

A

P2Y12 ADP receptor on platelet surface
1. doesn’t require bioactivation by metabolic enzymes (CYP3A4 substrate)

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12
Q

what is the half-life for cangrelor

A

3-5 min

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13
Q

what structure is this?

A

Aspirin

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14
Q

What structure is this?

A

clopidogrel

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15
Q

What structure is this?

A

prasugrel

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16
Q

What structure is this?

A

ticagrelor

17
Q

what is the mechanism for abiciximab and its role in therapy?

A
  1. it is a MAB
  2. Long duration of action- increased risk of bleeding
18
Q

what is the mechanism of action for eptifibitide and its role in therapy?

A
  1. synthetic peptide
  2. inhibits fibrinogen binding to dec. platelet aggregation
  3. cyclic heptapeptide derived from rattlesnake venon
19
Q

what is this structure?

A

eptifibitide

20
Q

Explain the mechanism of action of dipyridamole and differentiate them based on their structures and clinical properties.

A
  1. Opposing P2Y12 action (cAMP PDE inhibition and inhibition of adenosine uptake)
  2. with warfarin –> prosthetic heart valves
  3. with ASA –> ischemia
21
Q

Explain the mechanism of action of cilostazol and differentiate them based on their structures and clinical properties.

A
  1. Opposing P2Y12 action (cAMP PDE inhibition and inhibition of adenosine uptake)
  2. intermittent claudication
22
Q

what is this structure?

A

dipyridamole

23
Q

what is this structure?

A

cilostazol

24
Q

Explain the mechanism of action of vorapaxar

A

reversible PAR-1 receptor antagonist
1. used with aspirin and plavix
2. HL 3-4days ; anti-platelet effect persists for days after d/c

25
Q

what is this structure?

A

varapaxar

26
Q

T/F platelets have a nucleus?

A

false

27
Q

what are the two ADP receptor inhibitors? What is their pathway?

A
  1. P2Y1
    –> couple to Gq-PLC-IP3-Ca2+
  2. P2Y12
    –> couple to Gi and ACP
28
Q

T/F Activation of both ADP receptors is required for platelet activation?

A

true

29
Q

what is TTP (thrombotic thrombocytopenic purpura)?

A
  1. spurious and excessive platelet aggregation
  2. can be fatal
30
Q

what two P2Y12 antagonists have no metabolism necesary?

A
  1. ticagrelor
  2. cangrelor
31
Q

what is tirofiban used for?

A

combined with heparin to treat acute coronary syndrome

32
Q

what are PAR Inhibitors & what is their mechanism?

A

Mechanism: proteolytic cleavage of PAR-1 on platelet surface
1. they are GPCRs to release CA2+
2. thrombin activates platelets at nanomolar conc.

33
Q

what are the uses of clopidogrel?

A
  1. recent MI
  2. stroke
  3. established peripheral vascular disease and coronary stent procedures
34
Q

what structure is this?

A

Cangrelor

Exam 4 Antiplatelets PHRM 844 (3 decks)

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