Patient on anti-coagulant therapy

Question 1

what are the 2 main types of oral anticoagulants?

Answer 1

1. Vitamin K antagonists
2. Direct oral anticoagulants (DOACs)

Question 2

what is the purpose of anticoagulation?

Answer 2

to prevent thrombus formation in the veins where blood flow is slow

• thrombus consists of a fibrin web, platelets and RBCs

Question 3

what is an example of a vitamin K antagonist?

Answer 3

warfarin

• inhibits vitamin K dependent clotting factors eg X, IX, VII and II and protein C and S

Question 4

what are examples of DOACS?

Answer 4

• apixaban
• dabigatran
• edoxaban
• rivaroxaban

Question 5

what is the mechanism of action of apixaban, edoxaban and rivaroxaban?

Answer 5

reversible inhibition of factor Xa

• prevents thrombin generation and thrombus formation

Question 6

what is the mechanism of action of dabigatran?

Answer 6

reversible inhibition of free thrombin, fibrin-bound thrombin and thrombin-induced platelet aggregation

Question 7

what should be measured prior to starting warfarin?

Answer 7

baseline prothrombin

Question 8

what is warfarin licensed for?

Answer 8

1. Prophylaxis of embolism in rheumatic fever and AF
2. Prophylaxis in prosthetic heart valves
3. prophylaxis and treatment of DVT, PEs and TIAs

Question 9

when are DOACs preferred over warfarin?

Answer 9

1. non-valvular AF

AND

2. HF, HTN, previous stroke/TIA, >75yrs or DM

Question 10

which DOACS can be used for PE and DVT?

Answer 10

ALL

• apixaban
• dabigatran
• edoxaban
• rivaroxaban

Question 11

which DOACs can be used for VTE after hip/knee replacement?

Answer 11

• apixaban
• dabigatran
• rivaroxaban

Question 12

which DOACs can be used for prophylaxis after ACS or PAD?

Answer 12

rivaroxaban

Question 13

what are the contraindications of warfarin?

Answer 13

• haemorrhagic stroke
• significant bleeding
• severe hepatic impairment
• <72hrs post major surgery
• <48hrs postpartum
• drugs that interact with warfarin

Question 14

what can increase action of warfarin and therefore require dose decrease?

Answer 14

• weight loss
• acute illness
• smoking cessation

Question 15

what can decrease action of warfarin and therefore require dose increase?

Answer 15

• weight gain
• diarrhoea
• vomiting

Question 16

what is the main adverse effect of all anticoagulants?

Answer 16

BLEEDING!!!

Question 17

what are the side effects of warfarin?

Answer 17

• bleeding
• teratogenic (Teratogens are substances that cause congenital disorders in a developing embryo or fetus.)
• skin necrosis (decreased protein C > procoagulant state)

Question 18

what is important to inform patients taking rivaroxaban?

Answer 18

must be taken with food

Question 19

what are the contraindications of rivaroxaban?

Answer 19

• severe renal impairment
• active/risk of bleeding
• anti-phospholipid syndrome
• prosthetic valves
• liver disease affecting coagulopathy
• previous stroke/TIA

Question 20

what are the side effects of rivaroxaban?

Answer 20

• bleeding
• GI effects

Question 21

what is the reversal agent for warfarin?

Answer 21

• IV vit K 5mg
• prothrombin complex concentrate

Question 22

what is the reversal agent for rivaroxaban?

Answer 22

andexanet alfa

• recombinant form of human factor Xa protein

Question 23

how is warfarin monitored?

Answer 23

INR

• therapeutic range between 2-3
• variations within 0.5 units of target are ok