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PHRM844 > Anticoagulation / Antiplatelets > Flashcards

Anticoagulation / Antiplatelets Flashcards

1
Q

Hemostasis

A

Arrest of bleeding from a damaged blood vessel

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2
Q

Coagulation

A

Multi-step process to plug leaking vessel

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3
Q

Phases of hemostasis

A

Injury –> bleeding
Vasospasm
Platelet plug form –> adherence / aggregation
Fibrin clot form –> prothrombin -> thrombin
Fibrinolysis –> plasminogen -> plasmin

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4
Q

Deadly duo

A

Atherosclerosis plaque and thrombosis –>
coronary plaque rupture

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5
Q

Platelet composition

A

Presence of organelles and secretory granules, but no nucleus

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6
Q

Contact with ECM initiates platelet reactions

A

Adhesion and shape change
Secretion reaction
Aggregation

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7
Q

First step of platelet activation

A

Platelet adhesion and shape change

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8
Q

Platelet adhesion mediated by

A

GP Ia binding to collagen
GP Ib binding to von Willebrand factor

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9
Q

Shape changes facilitate receptor binding

A

Intact endothelial cells secret PGI2 to inhibit thrombogenesis

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10
Q

Second step of platelet activation

A

Platelet secretion

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11
Q

Secretion / release reaction

A

Degranulation ->
Platelet granules release ADP, TXA2, serotonin (5-HT) ->
ADP, 5-HT, TXA2 activate and recruit other platelets ->
TXA2 and 5-HT are potent vasoconstrictors

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12
Q

Third step of platelet activation

A

Platelet aggregation
Conformation of GP receptors to bind fibrinogen ->
Platelets are cross-linked ->
Form temporary hemostatic plug ->
Platelets contract ->
Form irreversibly fused mass ->
Fibrin stabilizes to anchor aggregated platelets ->
Forms surface clot

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13
Q

Antiplatelet drugs

A

COX-1 Inhibitors (aspirin)
ADP receptor inhibitors
BP IIb / IIIa receptor blockers
PDE-3 inhibitors
PAR inhibitors

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14
Q

COX-1 inhibitor (aspirin)

A

Inhibition of TXA2 synthesis -> anti-platelet activity
Irreversibly COX-1 inhibition by acetylation
Prolongs bleeding time

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15
Q

Aspirin indications

A

Prophylaxis and treatment of arterial thromboembolic disorders

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16
Q

Aspirin SEs

A

Upper GI bleeding
Acute aspirin overdose
Increased CVD risk

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17
Q

ADP receptors involved in activating platelets

A

P2Y1 and P2Y12
Activation of both is required for platelet activation by ADP

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18
Q

Direct acting P2Y12 antagonists

A

Cliostazol, ticagrelor, cangrelor

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19
Q

Pro-drug P2Y12 antagonists

A

Prasugrel, clopidogrel

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20
Q

ADP receptor inhibitor MOA

A

Irreversibly block ADP receptor on platelet and activates of GP IIb / IIIa complex

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21
Q

ADP receptor inhibitor administration

A

Taken orally
Clopidogrel has a lower toxicity profile
Action lasts for several days after dose

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22
Q

ADP receptor inhibitor uses

A

Recent MI, stroke, acute coronary syndrome

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23
Q

Thrombotic thrombocytopenic purpura

A

Spurious and excessive platelet aggregation
Can be fatal

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24
Q

Prasugrel

A

Used for: acute coronary syndrome
Taken orally
Prodrug: req esterases + CYP2A4 / 2B6
Irreversibly bind P2Y12 receptor
High bleeding risk

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25
Q

Ticagrelor

A

Used for: acute coronary syndrome, PCI
Taken orally
Binds to allosteric site, reversible
Faster onset of action
High bleeding risk

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26
Q

Cangrelor

A

Used adjunct for: PCI
Given IV
Binds reversibly
Fast onset of action

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27
Q

PDE-3 Inhibitors MOA

A

Platelet aggregation inhibitor
Action related to cAMP PDE inhibition and inhibiting adenosine uptake

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28
Q

Dipyridamole use

A

Adjunct with warfarin to prevent embolization from prosthetic heart valves
Adjunct with ASA to prevet cerebrovascular ischemia

29
Q

Cilostazol use

A

Intermittent claudication (muscle cramps)

30
Q

GP IIb / IIIa receptor inhibitors MOA

A

Inhibits fibrinogen crosslinking of platelets to decrease aggregation

31
Q

Eptifibatide

A

Given IV bolus followed by infusion up to 72 hours
Short duration of action
Used: prevent thromboembolism

32
Q

Tirofiban

A

Reversible inhibition
Given IV in dilute solution
Combined with heparin for acute coronary syndrome

33
Q

Abciximab

A

Given IV bolus followed by infusion
Long duration of action -> high bleeding risk
Adjunct with t-PA for early tx of acute MI

34
Q

PAR inhibitors

A

Thrombin activates platelets
GPCRs coupled to release Ca

35
Q

PAR inhibitors MOA

A

Proteolytic cleavage of PAR-1 receptors

36
Q

Vorapaxar

A

Oral administration
Used with aspirin or clopidogrel
Effects continue for days
Contra: history of stroke, TIAs, hemorrhage

37
Q

Vorapaxar use

A

Prevent thrombosis if previous MI or peripheral artery disease

38
Q

Clotting factors

A

Serine proteases:
- Factors XII, XI, X, IX, VII, II -> cleave and activate down-stream factors
- Protein C -> cleave factors Va, VIIIa to inactivate them

Glycoproteins:
- Factors VIII, V, III, Protein S -> cofactors for protease activation
- Anti-thrombin III -> binds and inhibits thrombin

39
Q

Fibrinogen/fibrin

A

Substrate protein for F IIa (thrombin)
Polymerizes to form clot

40
Q

Hemophilia A

A

Deficiency in factor VIII

41
Q

Hemophilia B

A

Deficiency in factor IX

42
Q

Clotting factor production

A

All produced in liver
Except von Willebrand factor is produced in endothelium
Liver disease can have unpredictable effects on coagulation

43
Q

Coagulation via extrinsic pathway

A

Requires tissue facto
Used when vessel is damaged and blood leaks out (thromboplastin)
Rapid clot formation ~15 seconds

44
Q

Thrombin in clotting pathways

A

Convergence point of intrinsic and extrinsic pathways at thrombin activation
Converts fibrinogen -> fibrin

45
Q

Coagulation via intrinsic pathway

A

Triggered when neg charged collagen is exposed on the wall of the blood vessel
Ex. blood in test tubes clotting

46
Q

Feedback mechs increase coagulation

A

Thrombin
- Activates factor V, VIII
- Enhances platelet activation
Platelet activation
- Increases factor VII, X activation
- Cleaves prothrombin

47
Q

Feedback mechs decrease coagulation

A

Antithrombin
- Neutralizes thrombin, factor Xa, IXa
- Accelerated by heparin
Protein C system
- Inactivates factor Va, VIIIa
Factor Xa
- Blocks initial activation of factor VII

48
Q

Platelet Count test

A

Too high: thrombocytopenia -> bone marrow malfunctions or nutritional deficiencies

49
Q

Prothrombin time (PT/INR) test

A

Plasma + thromboplastin + Ca
Clots in 12-14 seconds

50
Q

aPTT test

A

Plasma + phospholipid + activating agent
Clots in 26-33 seconds
Used to monitor heparin therapy

51
Q

Fibrinogen test

A

Less common
200-400 mg/dL

52
Q

D-dimer test

A

Product of fibrin breakdown

53
Q

INR ranges

A

Normal: 0.8-1.2
Therapeutic: 2-3
Risk of hemorrhage: >3

54
Q

Uses for anticoagulants

A

Prevent excessive clotting -> causes other issues if untreated
- Stroke
- Post-MI
- DVT
- PE

55
Q

Oral anticoagulant drugs

A

Coumarin anticoags
- All derivatives are water soluble lactones
- Warfarin is most common

56
Q

Warfarin MOA

A

Inhibits Vit K-epoxide reductase -> blocks reduction of Vit K epoxide back to active form
Inhibits synthesis of clotting factor II, VII, IX, X

57
Q

Warfarin OD

A

Discontinue warfarin
Administer Vit K
If serious can admin plasma instead

58
Q

Warfarin necrosis

A

Deficiency in protein C
Warfarin further decreases protein C levels so can cause initial incr in blood coag at start of therapy
Often common to start pts on heparin w warfarin in parallel

59
Q

Drug’s decr warfarin’s effects

A

Rifampin
Vitamin K
Pregnancy

60
Q

Drugs incr warfarin’s effects

A

SSRI’s
Broad spectrum antibiotics
Anabolic steroids

61
Q

Indirect factor IIa, Xa inhibitors

A

Heparin
- UFH
- LMWH (enoxaparin, daltaparin)
Non-heparinoids
- Fondaparinux

62
Q

Heparin MOA

A

Accelerated AT reactions -> inactivates thrombin and factor Xa

63
Q

Heparin clinical use

A

Admin IV -> immediate effect
Adjust dosing based on coag tests
Effects stop within hours of ending therapy

64
Q

Heparin AEs

A

Latrogenic hemorrhage
- Tx: protamino sulfate
HIT
- Type 1 and 2
Osteoporosis
- Associated with extended therapy

65
Q

HIT risk ranking

A

UFH > LMWH > fondaparinux

66
Q

Fondaparinux MOA

A

Indirectly inhibits factor Xa by selectively binding AT

67
Q

DOACs

A

Direct Xa inhibitors
- Rivoroxaban
- Apixaban
- Edoxaban
- Betrixaban
Direct thrombin inhibitors (DTI)
- Dabigatran

68
Q

Factor Xa inhibitor antidote

A

Andexanet - approved with apixaban and rivoroxaban

69
Q

DTI actions

A

Non-heparinoid parenteral agents
Inhibit free and fibrin-bound thrombin

PHRM844 (16 decks)

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