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Therapeutics 2 - Exam 4 > antiplatelets > Flashcards

antiplatelets Flashcards

hockerman

1
Q

what are the steps of homeostasis?

A

vasospasm (bleeding)
platelet plug formation
fibrin clot formation
fibrinolysis

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2
Q

what is the first phase of platelet activation?

A

platelet adhesion and shape change

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3
Q

what happens during platelet adhesion and shape change?

A

injury exposes collage (which binds to GP Ia)
vWF bridges collagen and GP Ib (thus allowing the platelet to attach to injury site)
shape change allows for a structure that enhance interaction with other platelets

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4
Q

what is the second phase of platelet activation?

A

platelet secretion

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5
Q

what happens in platelet secretion?

A

platelets degranulate to release granules containing ADP, TXA2, and 5-HT
signaling molecules recruit and activate nearby platelets

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6
Q

what is the third step of platelet activation?

A

platelet aggregation

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7
Q

what happens in platelet aggregation?

A

ADP, TXA2, and 5-HT activation of nearby platelets induce conformation of GPIIb/IIIAa receptors to bind fibrinogen
fibrinogen cross-links the platelet to form temporary plug
contract of platelets form irreversible fused mass
fibrinogen is converted into fibrin which stabilizes and anchors platelet together
surface for clot formation is formed

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8
Q

what does GP Ia bind to?

A

collagen

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9
Q

what does GP Ib bind to?

A

vWF (which is bridged to collagen)

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10
Q

what is ADP’s role?

A

activate and recruit other platelets after being activated by P2Y1 and P2Y12

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11
Q

what does P2Y1 do?

A

coupled to Gq and calcium pathways

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12
Q

what does P2Y12 do?

A

coupled to Gi pathway and inhibition of adenylyl cyclase

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13
Q

what does thromboxane a2 and serotonin do?

A

TXA2 and 5-H
activate and recruit other platelets
potent vasoconstrictors

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14
Q

what is the role of fibrinogen?

A

cross-links platelets together to form plug
once completed, it is converted into fibrin in the coag cascade to form clot

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15
Q

what does GPIIb/IIIa do?

A

binds fibrinogen
activated by the active forms of ADP, 5-HT, and TXA2

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16
Q

what is the MOA of aspirin?

A

irreversible inhibition of COX1 through acetylation to prevent the synthesis of TXA2 (which plays a key role in platelet aggregation)

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17
Q

why is a small dose of aspirin every day preferred?

A

it reduces the amount of TXA2 without interfering with prostacyclin production in tissues

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18
Q

what is the indication for aspirin?

A

prophylaxis and treatment of arterial thromboembolic disorders

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19
Q

what is the MOA of P2Y12 receptor antagonists?

A

irreversible block ADP receptors on platelet and subsequent activation of GP IIb/IIIa complex

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20
Q

what are the indications for P2Y12 drugs?

A

acute coronary syndrome
recent MI
stroke
established peripheral vascular disease
coronary stent procedures

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21
Q

what drugs are P2Y12 receptor antagonists?

A

clopidogrel
prasugrel
ticagrelor
ticlopidine
cangrelor

22
Q

what makes clopidogrel unique?

A

pro-drug, addition of SH group
activated by CYP2C19
lower toxicity profile

23
Q

what is TTP?

A

thrombotic thrombocytopenic purpura
decreases proteolytic activity (which cleaves vWF) causing spurious and excessive platelet aggregation
may be fatal

23
Q

what makes ticlopidine unique?

A

may induce TTP

24
Q

what makes prasugrel unique?

A

pro-drug, addition of SH group
also indicated for percutaneous coronary intervention
requires esterases and CYP3A4/2B6 to be come active
high risk of bleeding

25
Q

when is prasugrel not recommended?

A

in elderly
before CABG
due to high risk of bleeding

26
Q

what makes ticagrelor unique?

A

direct acting so does not require bioactivation by enzymes
CYP3A4 substrate
fast onset of action (7 to 9 hr half life)
risk of bleeding

27
Q

when should ticagrelor not be used?

A

immediately before CABG

28
Q

what makes cangrelor unique?

A

direct acting
reversible
short half life –> 3 to 5 minutes

29
Q

what is the MOA of GPIIb/IIa receptor inhibitors?

A

inhibits fibrinogen crosslinking of platelets

30
Q

what drugs are GP IIb/IIIa receptor antagonists?

A

abciximab
eptifibatide
tirofiban

31
Q

what is the indication for Abiciximab?

A

prevent thromboembolism in coronary angioplasty
combined with t-PA for early treatment of acute MI

32
Q

what is unique about abciximab?

A

monoclonal antibody directed against human GPIIb/IIIa
admin by IV bolus followed by infusion

33
Q

what is the duration of action for abciximab?

A

long
increases bleeding risk

34
Q

what is the indication for eptifibatide?

A

to prevent thromboembolism in unstable angina and angioplasty coronary procedures

35
Q

what is the duration of action of eptifibatide?

A

6 to 12 hours

36
Q

what is unique about eptifibatide?

A

synthetic peptide reversibly and selectively blocking GPIIb/IIIa
derives from snake venom
admin via IV bolus then infusion for 72 hours

37
Q

what is the indication for tirofiban?

A

combination therapy with heparin to treat acute coronary syndrome

38
Q

what is unique about tirofiban?

A

nonpeptide tyrosine analogous selective for GPIIb/IIIa and inhibits fibrinogen binding
IV admin in dilute solution
reversible

39
Q

what is the duration of action for tirofiban?

A

2 hour half life

40
Q

what is the MOA of PDE inhibitor?

A

inhibition of phosphodiesterase to inhibit platelet aggregation

41
Q

what is the indication of dipyridamole?

A

combined with warfarin to prevent embolization from prosthetic heart valves
combined with aspirin to prevent cerebrovascular ischemia

42
Q

what does the structure of dipyridamole look like?

A

two middle 6-membered N rings with 4 outward rings attached

43
Q

what is the indication for cilostazol?

A

intermittent claudication (leg pain)

44
Q

what does the structure of cilostazol look like?

A

far left has N 5-member ring structure

45
Q

what is the MOA of vorapaxar

A

reversible proteolytic cleavage of PAR-1 receptors on platelet surface

46
Q

what class of drug is vorapaxar?

A

protease activated receptor (PAR) inhibitor

47
Q

what is PAR-1 receptors coupled with?

A

GPCRs coupled to calcium which is used for thrombin

48
Q

what is the indication of vorapaxar?

A

combo therapy with aspirin or clopidogren in prophylactic prevention of thrombosis in patients with previous MI or peripheral arterial disease

49
Q

what is vorapaxar’s duration of action?

A

3 to 4 days with effect persisting after d/c

50
Q

what is unique about vorapaxar?

A

it should be avoided combination with strong CYP3A4 inhibitors (mycins, virs) or inducers (rifampin)

Therapeutics 2 - Exam 4 (9 decks)

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