Anticoagulants, Antiplatelets & Thrombolytics Flashcards Preview

Anticoagulants, antiplatelets & Thrombolytics > Anticoagulants, Antiplatelets & Thrombolytics > Flashcards

Flashcards in Anticoagulants, Antiplatelets & Thrombolytics Deck (74)
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1

Haemostasis

to stop bleeding in haemorrhage
Involves: local vasoconstriction, platelet aggregation and coagulation

2

Thrombosis

pathological, coagulation in the absence of bleeding
Involves: Virchow's triad

3

Virchow's triad

increase coagulation, vessel damage and abnormal blood flow

4

Arterial thrombus

white, platelet aggregation, embolus tends to cause stroke

5

Venous thrombus

red, white head, red-jelly tail, fibrin rich, embolus tends to lodge in lung: PE

6

Platelets in coagulation cascade

endothelial damage --> platelet aggregation--> mediator (pre-existing (ADP) and newly formed (TXA2)) release, further platelet aggregation

7

Fibrin in coagulation cascade

endothelial damage --> clotting factor release --> X activated (Xa) --> prothrombin --> thrombin (converts fibrinogen to fibrin (forms a fibrin mesh)

8

Fibrin clot formation

Platelet aggregation + blood coagulation

9

Thrombin

fibrinogen to fibrin

10

Platelet function

brings clotting factors closer together for activation

11

Activation of clotting factors

gamma-carboxylation

12

gamma carboxylation enzyme

carboxylase

13

Essential requirement of carboxylase?

vitamin K - therefore is required for coagulation

14

Warfarin target?

blocks vitamin K reductase - stopping vitamin K from binding to it (preventing gamma carboxylation and coagulation)

15

Anticoagulant function?

prevention/ treatment of venous thrombosis/ embolism

16

Caution with anticoagulants?

risk of haemorrhage

17

Which clotting factors does warfarin block?

II, VII, IX & X

18

How is warfarin standardly taken?

orally

19

Fast or slow action?

slow (2-3 days)

20

Half life?

long (40 hrs)

21

Warfarin warnings?

difficulty of balancing anticoagulance with haemorrhage risk - low therapeutic index

22

Factors that increase haemorrhage risk when on warfarin?

liver disease (less clotting factors)
fast metabolism (fast clotting factor clearance)
drug interaction: agents that inhibit hepatic metabolism of warfarin
drugs that inhibit platelet function (aspirin and NSAIDS)
drugs that inhibit reduction or availability of vitamin K

23

Factors that inhibit warfarin action (increase thrombosis risk)?

physiological state: pregnancy (higher clotting factor synthesis), hypothyroidism (less degradation of clotting factors), vitamin K consumption, drugs that increase the metabolism of warfarin

24

warfarin overdose treatment?

vitamin K or concentrate of clotting factors

25

Antithrombin III main function?

important inhibitor of coagulation

26

Action of antithrombin III?

neutralises serine protease factors (II, VII, IX, X) in coagulation cascade

27

Heparin mechanism?

binds to antithrombin III, increasing its affinity for serine protease factors, increasing the rate of clotting factor inactivation

28

What does heparin need to bind to to inhibit IIa (thrombin)?

Antithrombin III and IIa

29

What does heparin need to bind to to inhibit Xa

Antithrombin III

30

Examples of LMWHs?

enoxaparin, dalteparin

31

What do LMWHs inhibit?

factor Xa but not IIa (thrombin)

32

Heparin administration?

IV - immediate action
Subcutaneous - 1hr delay

33

How are LMWHs excreted?

Renal excretion

34

Adverse affects of heparin and LMWHs?

haemorrhage
osteoperosis (long term treatment)
hypoaldosteronism
hypersensetivity reactions

35

How to reverse heparin effects?

protamine sulphate

36

Orally active inhibitor action?

directly inhibits thrombin or Xa, to prevent venous thrombosis

37

Example of orally active inhibitor?

dabigatran etexillate

38

Advantages of orally active inhibitors?

administration convenience
predictable degree of anticoagulation

39

Disadvantages of orally active inhibitors?

No agent to reverse haemorrhage in overdose

40

Anti platelets act on which type of thrombosis?

arterial thrombosis

41

Anti coagulants act on which type of thrombosis?

Venous thrombosis

42

How to platelets attach to damaged vessels?

via surface glycoproteins and von williebrand factor (acts as a bridge)

43

Aggregation occurs due to which molecules?

ADP
5-hydrotrytamine (5-HT)
Thromboxane A2 (TXA2) via COX enzyme

These all cause cell surface receptors of platelets to express glycoprotein IIb/ IIIa

44

How do glycoproteins cross link platelets in platelet aggregation?

via fibrinogen

45

Acidic phospholipid exposure on platelet surface promotes the formation of?

Thrombin IIa - which stimulates further platelet aggregation

46

how is the mass of platelets stabilised?

Through the conversion of fibrinogen to fibrin

47

What is the role of ADP in platelet aggregation?

attracts more platelets

48

Role of TXA2 in platelet aggregation?

promotes platelet aggregation, degranulation and vasoconstriction

49

What is released when platelets degranulate due to TXA2?

more ADP and TXA2

50

Platelet aggregation mainly occurs in which form of clot formation?

haemostasis

51

What is the main anti platelet drug in use?

aspirin

52

how does aspirin work as an anti platelet?

blocks COX and prevents TXA2 synthesis
inhibits prostaglandin I2 production (TXA2 precursor)

53

side effects of aspirin?

GI bleeding and ulceration

54

Clopidogrel function?

links to P2Y12 receptor - irreversible inhibition

55

When is clopidogrel normally used?

when a patient is intolerant of aspirin

56

Aspirin administration?

normally oral

57

Clopidogrel administration?

oral

58

Tirofiban used when?

MI prophylaxis in high risk CV patients with unstable angina

59

Tirofiban short or long term drug?

short term

60

Tirofiban administration?

IV

61

plasminogen and fibrinolytic drugs act against what?

the coagulation cascade

62

What is the role of plasmin?

dissolves fibrin converting it into fibrin filaments

63

Plasminogen and fibrinolytic drugs act to do what?

reopen occluded arteries in acute MI or stroke

64

Administration of plasminogen and fibrinolytic drugs?

IV asap

65

What is preferred to the use of plasminogen and fibrinolytic drugs?

PCI if prompt

66

What does PCI entail?

non-surgical widening of coronary artery with stent placement after dilatation

67

What drug should be administered alongside PCI?

aspirin

68

Adverse effects of streptokinase?

Antibodies block action after 4 days
can cause allergies

69

When is streptokinase contraindicated?

In recent strep infection patients

70

What is alteplase (and duteplase)?

recombinant tissue plasminogen activator (rt-PA)

71

Benefits of alte/ duteplase?

no allergies

72

Administration of Alte/ duteplase?

short half life so IV infusion

73

MAJOR fibrinolytic adverse side effect?

haemorrhage

74

Control of haemorrhage due to fibrinolytic?

tranexamic acid - inhibits plasminogen activation