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Medical Pharmacology Exam 3 > Anticoagulants, antithrombotics and thrombolytics > Flashcards

Anticoagulants, antithrombotics and thrombolytics Flashcards

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USMLE® Step 1 flashcards
1
Q

What are the 2 major components of the hemostatic process?

A

Platelets (cellular)

Humoral (soluble) factors

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2
Q

What is the last step of the clotting cascade?

A

Fibrinogen to fibrin

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3
Q

Why is EDTA able to act as an anticoagulant?

A

Because calcium is a critical component of the clotting cascade and EDTA chelates it

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4
Q

What degrades fibrin? What is its precursor? What is the product of fibrin degradation?

A

Plasmin
Plasminogen
Fibrin degradation products

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5
Q

What are the three ways by which clotting pathway integrity can be assessed?

A 
Prothrombin time (PT)
Activated partial thromboplastin time (PTT)
Thrombin time (TT)
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6
Q

What factors are synthesized in the liver? (5)

A

2, 5, 7, 9, 10

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7
Q

What factors require vit K for gamma carboxylation? (5)

A

2, prothrombin, 7, 9, 10

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8
Q

What is unfractionated heparin? What is low molecular weight heparin?

A

Heparin in natural form - MW from 60K -100K daltons

Heparin with MW lower than 7K

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9
Q

How are low molecular weight heparins obtained? What is the source of heparin? (2)

A

Products of the degradation of heparin

Porcine and bovine sources

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10
Q

What are the 3 main factors within the clotting cascade that are inhibited by heparin?

A

Thrombin
Xa
IXa

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11
Q

What are 2 ways to test for heparin activity?

A

Prolongation of thrombin time

PTT

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12
Q

What are 2 ways heparin can be administered? Which is faster?

A

IV and SubQ

IV faster - immediate

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13
Q

Which has a longer half life, unfractionated or low molecular weight heparin?

A

Low molecular weight heparin

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14
Q

What are 2 major side effects of heparin therapy?

A

Bleeding

Thrombocytopenia

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15
Q

What are 2 possible effects of long term heparin use?

A

Osteoporosis

Hyperkalemia

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16
Q

What is an antagonist to heparin?

A

Protamine sulfate

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17
Q

What are the three examples of low molecular weight heparins provided?

A

Enoxaparin
Dalteparin
Fondaparinux

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18
Q

What are the 4 examples of direct thrombin inhibitors provided?

A

Lepirudin
Bivalrudin
Argatroban
Dabigatran etexilate

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19
Q

What is the prototype oral anticoagulant discussed?

A

Warfarin

20
Q

What is the mechanism of action of warfarin?

A

Blocks vit K gamma carboxylation of factors 2, 7, 9 and 10

Blocks vit K gamma carboxylation of proteins C and S

21
Q

What is a standard way to monitor warfarin activity?

A

INR - International normalized ratio

22
Q

Where is warfarin metabolized (2)? Failure of which organ system impacts whether warfarin should be used at all?

A

Kidney and liver

Liver failure

23
Q

What can decrease warfarin absorption from the GI tract? What is the effects of barbiturates, phenytoin and alcohol on warfarin? What is the effect of vit K on Warfarin?

A
  • Cholestyramine
  • Induce CYPs, increased metabolic clearance of warfarin
  • vit K antagonizes warfarin
24
Q

What is the major toxicity for warfarin? What class of drugs can worsen this toxicity?

A

Bleeding

NSAIDs

25
Q

How can frozen plasma be used to treat warfarin overdose? How is this different from treating heparin overdose?

A

infusion of fresh plasma and vit K can counteract warfarin overdose. Not possible for heparin

26
Q

Why can’t warfarin be used in pregnant women? What is a potential effect of high initial dosages of warfarin?

A

It is a teratogen

Can cause coumadin-induced skin necrosis

27
Q

What are 2 examples of antihemolytic products that are available as concentrates?

A

Factor VIII and Factor IX

28
Q

How is streptokinase activated? Why must a large loading dose be used during treatment? Why is streptokinase use limited to a short period of time?

A

Forms 1:1 complest with plasminogen
Large dose needed to overcome neutralizing antibodies
Because antibodies will form to streptokinase

29
Q

Unlike other thrombolytics, why is Streptokinase likely to cause anaphylaxis and fever?

A

Most people will already have antibodies (or will develop) to the strep product

30
Q

What is the source of urokinase? How is the half life compared to streptokinase? Where is it metabolized?

A

Human cells
Only 15 mins (half of streptokinase)
Metabolized in liver

31
Q

What is the source of tissue plasminogen activator (tPA)? What is its half life? What is the ramification?

A

Recombinant DNA technology
Only 3 mins
Must be admin. as continuous infusion

32
Q

How do “CPR within 10 days” and “previous cerebrovascular accident” relate to thrombolytics?

A

These are contraindications for the use of thrombolytics

33
Q

What do aspirin, ticlodipine and clopidogrel have in common?

A

They are all inhibitors of platelet aggregation

34
Q

What is the mechanism by which ticlopidine and clopidogrel block platelet aggregation?

A

Bind purinergic receptor and prevent ADP binding. ADP binding necessary for platelet shape change and aggregation

35
Q

What is a severe toxicity noted with ticlopidine? With clopidogrel?

A

ticlopidine - neutropenia in 1% of patients

Clopidogrel - thrombotic thrombocytopenia purpura

36
Q

What is abciximab? What is its mechanism?

A

Human-mouse monoclonal Ab

- Binds platelet GPIIb/IIIa, blocks fibrinogen binding to platelets and platelet aggregation

37
Q

What is tirofiban? What is its mechanism? What is an advantage over abciximab?

A

Small molecule inhibitor of GPIIb/IIIa

  • Binds GPIIb/IIIa, blocks fibrinogen binding to platelets and platelet aggregation
  • Short duration of action, easier to reverse
38
Q

What factor converts fibrinogen to fibrin?

A

Factor 2a

39
Q

What factor activates factor 2? What are 3 necessary cofactors?

A

Factor 10a

- Factor 5a, Calcium, Platelets

40
Q

What factor activates factor 9? What are 3 necessary cofactors?

A

Factor 9a

- Factor 8a, Calcium, Platelets

41
Q

How is factor 9 activated?

A

Contact system, previously activated factor 9a

42
Q

In addition of factor 9, what else can activate factor 10? What are 2 required cofactors?

A

Factor 7a

tissue factor, calcium

43
Q

What other factor (beyond 9a) can activate factor 9? What are necessary cofactors (2)?

A

Factor 7a

Tissue factor and Calcium

44
Q

What molecule must heparin be bound to for it to inhibit thrombin, 10a and 9a?

A

ATIII

45
Q

What are the 3 direct thrombin inhibitors that must be administered IV? What is 1 direct thrombin inhibitor that can be administered orally?

A 
IV
lepirudin (renal clearance)
bivalirudin
argatroban (hepatic clearance)
Oral 
dabigatran etexilate

Medical Pharmacology Exam 3 (13 decks)

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