11.2 Anticoagulants

Question 1

how is antithrombin 3 linked to clotting factors?

Answer 1

endogenous inactivator of CFs

Question 2

how are coagulation factors in the blood? benefit?

Answer 2

zymogens

activated locally for fine control

Question 3

function of purple blood tube

Answer 3

EDTA chelates calcium, prevents sample clotting

Question 4

function of blue blood tube

Answer 4

can add calcium back in to get a clotted sample if needed

Question 5

pharmacodynamics of UFH

Answer 5

fast onset,
half life 30mins-2 hours
unpredictable elimination

Question 6

how is UFH able to catalyse inhibition of 2a?

Answer 6

binds simultaneously to 10a and 2a

Question 7

example of LMWH, and a synthetic version

Answer 7

dalteparin

fodaparinux

Question 8

half life of LMWH

Answer 8

over 2 hours, more predictable

Question 9

why could heparins cause hyperkalameia

Answer 9

inhibit aldosterone secretion

Question 10

contraindications of heparins

Answer 10

clotting disorders
renal impairment

Question 11

DDIs for heparins

Answer 11

other antithrombotics
ACEi/ARB or K+ sparing, due to hyperkjalameia

Question 12

how is UFH titrated?

Answer 12

activated partial thromboplastin time

Question 13

vit K antagonist mechanism of action

Answer 13

competitive inhibition of VKOR

Question 14

vit k dependent clotting factors

which is most sensitive? usefulness?

Answer 14

2.7.9.10

7, used in prothrombin time

Question 15

why might there be a delayed onset of action for vit K antagonists?

Answer 15

circulating active clotting factors are present for several days, need to be cleared and replaced with inactive forms

Question 16

link warfarin and NSAIDs

Answer 16

NSAIDs decrease GI absorption of vit K, increase INR so more anticoagluated so high bleed risk

Question 17

INR target for DVT, PE, AF

Answer 17

2.5

Question 18

INR target is recurrent DVT or PE and on anticoagulants

Answer 18

3-3.5

Question 19

how do the 2 classes of DOACs work? give example drugs

Answer 19

direct Xa inhibition, inhibit both free Xa and that bound with antithrombin 3, not directly affecting 2a
e.g. apixaban, rivaroxaban

direct competitive 2a inhibitor, circulating and thrombus bound
e.g. dibigatran

Question 20

benefits of DOACs

Answer 20

oral, little direct monitoring, take at home

Question 21

DOAC ADRs

Answer 21

bleeding
skin reactions

Question 22

AF score for DOAC

Answer 22

ORBIT/HASBLED

Question 23

contraindications of DOAC

Answer 23

low creatinine clearance for dibigatran
pregancy

Question 24

DDIs for DOAC

Answer 24

CYP inhibitors/inducers