Anticoagulants

Question 1

indications for anticoagulant drugs

Answer 1

arterial disease (anti-platelets & anticoagulants)

• coronary artery disease
• cerebrovascular disease
• peripheral vascular disease

thromboembolic disease (anticoagulants)

• AF
• VTE
• prosthetic heart valves

Question 2

mechanism of unfractionated heparin

Answer 2

• binds anti-thrombin 3 –> increases activity
  - inactivates thrombin (IIa), Xa
• requires APTT monitoring
• reversed with protamine

Question 3

pharmacokinetics of UH

Answer 3

• must be given parenterally (IV or SC) CANT be absorbed
• rapid onset and offset
• varied molecular weight

Question 4

adverse effects of UH

Answer 4

• bleeding = intracranial, injection sites, GI loss, epistaxis
• heparin-induced thrombocytopenia (autoimmune against platelets)
• osteoporosis (long-term)

Question 5

LMWH

Answer 5

• smaller chains than UH
• binds to anti-thrombin III, doesn’t inactivate thrombin, instead specifically Xa
• lower risk of bleeding, HIT and osteoporosis

Question 6

pharmacokinetics of LMWH (compared to UH)

Answer 6

• longer half-life
• more predictable dose-response relationship
• higher bioavailability

Question 7

disadvantages of LMWH

Answer 7

• cant be monitored by APTT
• not fully reversible by protamine
• cleared by kidneys

Question 8

indications for LMWH

Answer 8

• non-STEMI, STEMI

- initial treatment of VTE / PE

Question 9

mechanism of warfarin

Answer 9

vitamin K antagonist
- inhibits synthesis of vitamin K dependent coagulation factors e.g. VII, IX, X, II

• slow onset of anticoagulant action due to turnover of circulating factors

Question 10

indications for warfarin

Answer 10

tx of venous or arterial thrombosis
- VTE/PE

prevention of venous or arterial thromboembolism

• mechanical heart valves
• AF

Question 11

warfarin metabolism

Answer 11

• crosses placenta (dont use in pregnancy)
• metabolised by CYP
  - CYP450 inhibitors = higher INR
  - CYP450 inducers = lower INR

Question 12

adverse effects of warfarin

Answer 12

• haemorrhage (older people w/ previous bleeds)

- teratogenic

Question 13

monitoring of warfarin

Answer 13

• titrate dose with INR
• checked every month
• various therapeutic ranges depending on cause

Question 14

management of high INR

Answer 14

depends on the severity of the bleed

• IV vitamin K (slow onset, long duration)
• IV prothombinex

Question 15

describe dabigatran

Answer 15

• warfarin alternative
• direct thrombin inhibitor
• renal excretion
• often used in patients with AF and VTE
• not CYP450 dependent

Question 16

dabigatran antidote

Answer 16

idarucizumab