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Blood and Lymph Unit 3 > Pharmacology of Anticoagulation Therapy > Flashcards

Pharmacology of Anticoagulation Therapy Flashcards

1
Q

Name the anticoagulant drugs that interfere with the coagulation cascade and prevent formation of thrombin, which converts fibrinogen to fibrin.

A

Heparin and oral anticoagulants

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2
Q

What agent promotes lysis of clots by increasing formation of plasmin, a serine protease that degrades fibrin?

A

Fibrinolytic agents

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3
Q

What drug inhibits the formation of platelet products or blocks platelet adhesion thus preventing platelet aggregation and clot formation?

A

Anti-platelet agents

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4
Q

What are the three forms of Heparin?

A
  1. Unfractionated Heparin
  2. Low molecular weight heparins
  3. Fondaparinux
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5
Q

Describe unfractionated heparin.

A
  • Proteoglycans containing covalently linked sulfated polysaccharide chains
  • 12,000 Daltons
  • Highest negative charge density
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6
Q

Describe low molecular weight heparins like

  • lovenox
  • enoxaparin
  • dalteparin
  • nadroparin
A
  • produced by chemical or enzymatic depolymerization of heparin
  • 4,500 Daltons
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7
Q

Describe Fondaparinux (Arixtra)

A

Synthetic pentasacharide

Minimal sequence in heparin for binding antithrombin

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8
Q

What is the mechanism of action of heparin?

A

Heparins bind antithrombin III

Antithromin III is a natural protease inhibitor that inactivates coagulation factors

Heparin accelerates the rate of decay of IXa, Xa, and XIIa by antithrombin III

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9
Q

Which type of heparin is able to bind to the antithrombin/thrombin complex?

A

Unfractionated

LMWH and Fondaparinux can only bind AT-III

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10
Q

Which drug does not absorb well from the GI tract and can’t be given orally. This drug also has poor bioavailability and relatively short half-life?

Hint: Requires careful monitoring in hospital but can be given to pregnant women.

A

Unfractionated heparin

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11
Q

What drug is given SQ, has a long half life, requires less monitoring, and has a better bioabailability than unfractionated heparin?

A

Low molecular weight heparins and fondaparinux

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12
Q

What conditions would you use heparins to treat?

A

-Venous thrombosis and pumonary embolism
-management of unstable angina or acute myocardial infarction
-During and after coronary angioplasty or stent placement
During surgery requiring cardiopulmonary bypass
-Kidney dialysis

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13
Q

What drug can you use to reverse the toxic affects of heparin?

A

Protamine sulfate, a positively charged compound that neutralizes heparin

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14
Q

Name three toxic effects of heparin.

A
  1. Bleeding
  2. Heparin-induced thrombocytopenia syndrome (HIT)
  3. Allergic Events
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15
Q

Describe the onset of heparin-induced thrombocytopenia syndrome.

A

Platelet cound decreases 5-10 after heparin

Caused by development of antibodies that bind to and activate platelets resulting in a prothrombotic state

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16
Q

What is the treatment for patients who have heparin-induced thrombocytopenia syndrome?

A

TX with direct thrombin inhibitors:

  • Argatroban (Novastan): a small molecule inhibitor
  • Lepirudin (Refludan): recombinant form of hirudin, the antivoagulant from leeches
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17
Q

Allergic reactions are sometimes seen in patients on Heparin. What is the root cause of thos allergic reaction?

A

Contaminant over sulfated chondroitin sulfate

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18
Q

What drug is a derivative of dicumarol and is a vitamin K analogue?

A

Warfarin

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19
Q

What is the mechanism of action of warfarin?

A

Warfarin inhibits reductases that reduce vitamin K.

Reduced vitamin K is used as a cofactor for certain enzymes

These enzymes undergo vitamin K-dependent gamma carboxylation of N-terminal glutamate

20
Q

What are the pharmacokinetic characteristics of warfarin?

A

It is readily absorbed
Good bioavailability
Does not achieve affect until 2-3 days

21
Q

What are the clinical uses of warfarin?

A

Used to prevent:

  • Venous thromboembolism
  • Systemic embolism in patients with prosthetic heart valves or atrial fibrillation
  • Stroke, recurrent infarction, or death in patients with acute myocardial infarction
22
Q

What are some of the adverse effects of warfarin?

A

Hemorrhage
TX: Drug stopped, Vitamin K administered, Plasma can be transfused to replace coag. factors

Teratogenic

23
Q

What drugs can increase the action of warfarin?

A
  1. Drugs that inhibit platelet function (aspirin)
  2. Drugs that decrease vit. K synthesis by intestinal microbes (antibiotics)
  3. Drugs that replace warfarin from plasma proteins (clofibrate, phenytoin)
    - Drugs that reduce the metabolism and elimination of warfarin in the liver
24
Q

What drug decrease the effect of warfarin?

A
  • Drugs that increase the metabolism by inducing metabolic enzymes in the liver (barbiturates, rifampin)
  • Drugs that decrease warfarin absorption from the GI tract (cholestyramine)
25
Q

There are new oral anticoagulants that are direct thrombin or Factor Xa inhibitors. Name some advantages of these drugs.

A
  • Rapid onset of action
  • Absence of food interactions
  • Do not require monitoring
26
Q

There are new oral anticoagulants that are direct thrombin or Factor Xa inhibitors. Name some disadvantages of these drugs.

A
  • Contraindicated with kidney disease
  • Greater GI bleeding than with warfarin
  • Short half-life
  • Cost
  • No antidote available to reverse effects
27
Q

There are new oral anticoagulants that are direct thrombin or Factor Xa inhibitors. Name three of these new drugs.

A
  • Dabigatran etexilate: Prodrug, lowers rate of stroke and systemic embolism, less intracranial hemorrhage. More myocardial infarctions
  • Apixaban
  • Rivaroxaban- Synthetic, lower rates of strokes and emboli for the TX or atrial fibrillation

All three have been approved for the treatment of atrial fibrillation

28
Q

What is the mechanism of action for fibrinolytic agents?

A

Convert plasminogen to plasmin, a protease that degrades fibrin clots.

29
Q

What is tissue plasminogen activator and what is its mechanism of action?

A
  • Serine protease

- Fibrinolytic drug that binds to fibrin, which increases cleavage of plasminogen to plasmin.

30
Q

What is urokinase (u-PA)?

A

Enzyme obtained from renal cells in culture that converts plasminogen to plasmin

DOES NOT BIND FIBRIN

31
Q

What is streptokinase?

A

Non-enzymatic protein obtained from beta-hemolytic streptococci.

-forms a complex with plasminogen which becomes activated and converts plasmin

32
Q

What are fibrinolytic agents used in the the treatment for?

A

-Acute myocardial infarction
-Ischemic stroke
-Deep vein thrombosis
Pulmonary embolism

33
Q

What are some adverse effects of fibinolytic agents?

A

Hemorrhage
Induced systemic lytic state
Allergic reaction due to antibodies against Streptokinase

34
Q

What are antiplatelet drugs used to treat?

A

Acute coronary syndrome

35
Q

What are the three classes of anti-platelet drugs?

A
  • Those that inhibit formatio of platelet products (Aspirin)
  • Those that prevent activation/aggregation (ADP receptor antagonist)
  • Those that block adhesion proteins (Glycoprotein IIb/IIIa Inhibitors)
36
Q

What is the mechanism of action of aspirin?

A

Irreversibly inactivates cyclooxygenase preventing thromboxane A2 formation by platelets

Permanent- for the lifespan of the platelet 7-10 days

Used in prevention of AMI of patients with artherosclerosis

37
Q

What are two ADP receptor antagonist?

A

Thienophyridines

  • Clopidogrel (Plavix)-used in pts. w/ aspirin intol.
  • Ticlopidine
  • Prasugrel- most potent
38
Q

What is the mechanism of action of ADP receptor antagonists?

A

They block platelet activation by ADP which inhibits secretion of alpha granules and blocks expression of adhesion proteins GPIIb/IIa

39
Q

What is the pharmacokinetics of ADP receptor antagonists?

A

slow onset of action because they are prodrugs that have to be metabolized by the liver

40
Q

Is the action of ADP receptor antagonists permanent?

A

Yes so for the lifespan of that platelet

41
Q

What is ADP receptor antagonist used to treat?

A

Preventing cardiac events in patients with atherosclerosis

42
Q

Describe Ticagrelor.

A

Oral ATP analogue that binds reversibly to ADP receptor
Rapid action
Greater platelet inhibition
Reduced rate of death from MI without increasing major bleeding

43
Q

What are glycoprotein IIb/IIIa inhibitors?

A

Adhesion protein on the surface of platelets that is a receptor for fibrinogen

Inhibitors block the receptor and prevent platelet aggregation

44
Q

Name three glycoprotein IIb/IIIc inhibitors.

A

Abciximab-Monoclonal antibody agains the glycoprotein receptor. Used in coronary angioplasty. Prevents restenosis, recurrent AMI
Eptifibatide- Cyclic peptide inhibitor used for unstable angina
Tirofiban- small molecule inhibitor used or treatment of unstable angina

45
Q

What are the adverse affects of glycoprotein IIb/IIIc inhibitors?

A

Bleeding and thrombocytopenia

Reverse by platelet infusion

Blood and Lymph Unit 3 (12 decks)

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