Antiplatelets and Anticoagulants

Question 1

How is arterial thrombosis managed?

Answer 1

Anti-platelets

Question 2

How is venous thrombosis managed?

Answer 2

Anti-coagulants

Question 3

What is the mechanism of action of aspirin?

Answer 3

Inhibits cyclo-oxygenase which is necessary to produce thromboxane A2

Question 4

What are some of the possible side effects of aspirin?

Answer 4

Bleeding

Bronchospasm

Question 5

What is the mechanism of action of clopidogrel and prasugrel? (anti-platelets)

Answer 5

ADP receptor antagonists

Question 6

What is the mechanism of action of dipyridamole? (anti-platelet)

Answer 6

Phosphodiesterase inhibitor which reduces the production of cAMP which is a second messenger in platelet activation

Question 7

What is the mechanism of action of abciximab? (anti-platelet)

Answer 7

GP IIb/ IIIa inhibitor which inhibits aggregation

Question 8

How long before surgery should anti-platelets be stopped?

Answer 8

7 days prior to surgery

This is because anti-platelets affect platelet function for their life span which is 7 days long

Question 9

Which drug is first line for acute thrombosis?

Answer 9

Heparin

*Has an immediate effect

Question 10

How long is heparin given for after an acute incident?

Answer 10

6 months

Then switch to oral anticoagulants to avoid lifelong injections

Question 11

What are the two forms of heparin?

Answer 11

Unfractioned

LMWH

Question 12

How are the different forms of heparin monitored?

Answer 12

APTT - unfractioned

Anti-Xa assay - LMWH

Question 13

What are some of the possible complications of heparin?

Answer 13

Bleeding

Heparin induced thrombocytopenia (HITT)

Osteoporosis (when used long-term)

Question 14

How is heparin reversal achieved?

Answer 14

Stop the heparin

Protamine sulphate (if bleeding is severe) 
- this binds to and turns off heparin

Question 15

Give some examples of coumarin anticoagulants

Answer 15

Warfarin

Phenindione

Acenocoumarin

Phenprocoumon

Question 16

What is the mechanism of action of the coumarin anticoagulants?

Answer 16

Inhibition of vitamin K

Question 17

What is the mechanism of action of vitamin K?

Answer 17

Carboxylation of clotting factors

Question 18

What factors are vitamin K dependent?

Answer 18

Factors II, VII, IX and X

Protein C and S

Question 19

What is the mechanism of action of warfarin?

Answer 19

Blocks the ability of vitamin K to carboxylate clotting factors

Question 20

How is warfarin therapy monitored?

Answer 20

INR

Question 21

What are some of the possible complications of warfarin therapy?

Answer 21

BLEEDING:

Skin bruising

Epistaxis

GI bleeds

Intracerebral bleeds

Question 22

How is warfarin reversal achieved?

Answer 22

Omit warfarin dose

Administer oral vitamin K

Administer clotting factors (FFP or factor concentrates)

Question 23

What are the indications for use of the new anticoagulants?

Answer 23

Used instead of LMWH as prophylaxis in elective hip and knee replacement surgery

Used for selected patients for stroke prevention in AF

Used for treatment of DVT/ PE

Question 24

What is the mechanism of action of dabigatran?

Answer 24

Directly inhibits thrombin

Question 25

What is the mechanism of action of rivaroxaban and apixaban?

Answer 25

Xa inhibitors

Xaban = Xa inhibitors