Anticoagulants

Question 1

List the following anticoagulants in order of quickest to longest onset of action

• warfarin
• rivaroxaban/
  dabigatran
• subcut heparin
• enoxaparin
• apixaban

Answer 1

1. SC heparin (immediate onset)
2. Dabigatran, rivaroxaban AND apixaban (all within 30 mins)
3. Enoxaparin (within 3 hours)
4. Warfarin (36-72 hours)

Question 2

What is the appropriate antidote for

1. Warfarin
2. LMWH eg enoxaparin
3. Dabigatran
4. Heparin

Answer 2

1. Vitamin K
2. No complete antidote - protamine partially effective
3. Idarucizumab
4. Protamine (usually ceasing tx is sufficient though)

Question 3

List 5 risk factors associated with thromboembolism

Answer 3

• temporary immobility
• paralysis
• thrombotic disorders
• obesity
• age >40
  (Also malignancy, previous thromboembolism)

Question 4

What is the primary indicator of heparin induced thrombocytopenia, and at what stage should heparin/LMWH be withheld?
How often after starting treatment does HIT occur (usually)?

Answer 4

Low platelet count, tx usually withheld if platelet count drops 30-50% below baseline (and substitute anticoagulant)
HIT usually presents between days 5-10 of treatment (but can occur up to weeks after ceasing heparin)