Oral Anticoagulants Flashcards Preview

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Flashcards in Oral Anticoagulants Deck (21):
1

The most commonly used Vitamin K antagonist is?

Warfarin (Coumadin)

2

Warfarin
MOA

Suppress functional forms of factors 2, 7, 9, 10. Prevents carboxylation of glutamic acid in these proteins by blocking the epoxide reductase enzyme in the liver

3

Why is carboxylation of coagulation factors important? Which factors require gamma-carboxylation for activation?

Factors 2, 7, 9, 10

Carboxylation is essential for Ca2+ binding

4

Warfarin
Onset of Action

Very long onset of action. Typically heparin is given in emergency situations and warfarin is for long term use

5

Warfarin
Absorption

Very well absorbed orally

6

Warfarin
Does it have a short or long half life and why?

Long half life (36 hrs) due to high protein binding to plasma albumin

7

Warfarin
Metabolism

Activated by enzymes in the hepatic ER. Varies greatly from patient to patient

8

Which secondary hemostasis pathway does warfarin effect most? What test can be used to assess the effects of warfarin?

Extrinsic pathway (though decreasing functionality of 2, 7, 9, 10)

PT/INR (prothrombin time/international normalized ratio) used to assess anticoagulant effects of warfarin

9

Therapeutic Range of Warfarin

1.5x baseline PT/INR is considered therapeutic

10

Warfarin Drug Interactions
How do other drugs cause warfarin potentiation?

-Cause a vitamin K deficiency
-Decrease clotting factor synthesis
-Suppression or competition for microsomal enzymes

11

Warfarin Drug Interactions
How do other drugs inhibit the anticoagulant effects of warfarin?

Decrease warfarin absorption
Enhance warfarin metabolism

12

Warfarin
Toxicity

Hypoprothrombinemia
Ecchymoses, purpura, hematuria, hemorrhage

Coumadin induced necrosis due to warfarin causing impaired functionality of protein C

Fetal malformation

13

Who should never receive warfarin?

Pregnant women. All oral anticoagulants can cross the placental barrier and cause fetal malformation

14

What could you give a patient who has overdosed on warfarin?

-Fresh frozen plasma will replace factors 2, 7, 9, 10

-Vitamin K via IV will reverse warfarin's effects

15

Vitamin K
Function

Essential for attaching a Ca2+ binding functional group (y-carboxyglutamic acid) to prothrombin.

Required for synthesis of clotting factors 2, 7, 9, 10

16

Vitamin K Therapeutic Use

Drug induced hypoprothrombinemia
Used in hypoprothrombinemias of newborns

17

Vitamin K Toxicity

Pretty non-toxic. May cause hemolysis in some infants or individuals sensitive to primaquine

18

List the Anti Xa agents

Rivaroxaban
Apixiban
Edoxaban

19

List the Anti thrombin agents

Dabigatran

20

Features of the new oral anticoagulant drugs

You do not have to monitor these drugs! (Unfortunately, there are no tests to monitor their efficacy).

Often have fixed, once daily dosing

All cleared by the renal system

Have a shorter half life than warfarin

21

Who should never receive dabigatran?

Someone with severe renal impairment. Dabigatran has 100% renal clearance

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