(THER) Heparin Anticoagulants II [Warfarin]

Question 1

The structure of warfarin is very similar to the structure of…

Answer 1

Vitamin K (that is how it is able to block its functioning).

Question 2

When would we use heparin vs warfarin?

Answer 2

Heparin = ER or places where we need more rapid onset

Warfarin = chronic care usage

Also, heparin can be used in pregnancies. warfarin CANNOT!

Question 3

What is the route of administration for Warfarin?

Answer 3

PO

Question 4

What accounts for the long half-life of warfarin?

Answer 4

It is due to binding to plasma albumin (warfarin is about 97% bound)

Question 5

Where is warfarin metabolized?

Answer 5

Liver (CYP3A4)

Question 6

What is one way that diet can affect oral anticoagulant function?

Answer 6

If a patient eats dark leafy greens, they’ll get exogneous vitamin K. Warfarins function is predicated on blocking the body’s endogenous vitamin K formation so this diet will render warfarin near useless.

Question 7

How can antibiotics interact with warfarin function?

Answer 7

Antibiotics kill gut flora which is used by the body for vitamin K formation. A drop in vitamin K by antibiotics + the drop in vitamin K from warfarin may cause issues of bleeding.

Question 8

Describe the teratogenicity of warfarin

Answer 8

It can cross the placental barrier and cause fetal bone malformation.

Question 9

Coumadin induced necrosis

Answer 9

Among other effects, warfarin can also impair the functionality of protein C. This can paradoxically, cause a drop in anti-coagulation causing thrombosis.

Question 10

Treatments for oral anticoagulant overdose (3)

Answer 10

1. Replacement of 4 factors. Infusion of whole fresh blood or frozen plasma
2. Recombinant factor VIIa
3. Vitamin K

Question 11

What is the function of vitamin K ? (2)

Answer 11

1. It is essential to the attachment of a calcium binding functional group to prothrombin protein.
2. Co-factor for the functional synthesis of clottable coagulation factors II, VII, IX and X

Question 12

Name the new oral anticoagulants (3) and their general mechanism of action (2)

Answer 12

• Anti-Xa agents
  
  • Rivaroxaban (Xarelto)
  • Apixiban
• Antithrombin Agents
  
  • Dabigatran

Question 13

Rivaroxaban Target

Answer 13

Factor Xa

Question 14

Rivaroxaban renal clearance percentage

Answer 14

65%

Question 15

Rivaroxaban interactions

Answer 15

potent CYP3A4 inhibitors

Question 16

Apixiban target

Answer 16

Factor Xa

Question 17

Apixiban renal clearance percentage

Answer 17

25%

Question 18

Apixiban interactions

Answer 18

potent CYP3A4 inhibitors

Question 19

Dabigatran target

Answer 19

Factor IIa (thrombin)

Question 20

Dabigatran renal clearance percentage

Answer 20

100%

Question 21

Dabigatran interactions

Answer 21

proton pump inhibitors

Question 22

What is the half-life of rivaroxaban/apixiban/dabigatran compared to warfarin (general terms)?

Compare their coagulation monitering

Answer 22

Signficantly shorter

No need (or ability) to moniter anything but warfarin

Question 23

Warfarin MOA

Answer 23

Competitive antagonist of vitamin K. Suppresses the synthesis of functional forms of factors II, VII, IX and X

Question 24

Warfarin monitoring

Answer 24

prothrombin time/ INR

Question 25

Warfarin indications (2)

Answer 25

Prolonged treatment of DVT and Atrial Fibrillation

Question 26

Warfarin side effects/toxicity (3)

Answer 26

Bleeding, coumadin induced necrosis

Has interaction with several medications which results in bleeding due to potentiating the effect of warfarin

Question 27

Vitamin K indications (3)

Answer 27

1. Hypoprothrombinemia
2. intestinal disorders and gastrectomy
3. reverses the effects of warfarin

Question 28

Side effects/toxicity of vitamin K

Answer 28

hemolysis

Question 29

Oral Anti-Xa: Rivaroxaban/Apixaban indications (2)

Answer 29

1. Stroke prevention in patients with AF
2. Rivaroxaban also approved for prophylaxis and treatment of DVT

Question 30

Oral Anti-Xa: Rivaroxaban/Apixaban toxicity (2)

Answer 30

Bleeding; liver toxicity

Question 31

Oral Antithrombin: Dabigatran indications

Answer 31

Stroke prevention in patients with AF

Question 32

Oral Antithrombin: Dabigatran toxicity (2)

Answer 32

Bleeding; liver toxicity