Anticoagulation

Question 1

What tends to drive clot formation in:

a) venous and intracardiac systems
b) arterial system

Answer 1

a) coagulation cascade

b) platelet activation

Question 2

what is used as primary prevention for venous thromboembolism (DVTs and PEs)?

Answer 2

Heparin (usually LMWH)

Question 3

Name two examples of heparins

Answer 3

enoxaparin

dalteparin

Question 4

how are heparins administered and what is used to work out the dose?

Answer 4

subcutaenously

use weight to work out dose (200 units/kg)

Question 5

what is the mechanism of action of heparins?

Answer 5

increase activity of antithrombin which inactivates clotting factors.

Question 6

what can be used for primary prevention of DVT and PE other than heparins?

Answer 6

fondaparinux or DOACs

Question 7

in what patients might you use unfractionated heparin to treat DVT or PE?

Answer 7

renal impairment

patients with an increased risk of bleeding

Question 8

after starting warfarin, why do you have to continue giving a LMWH for 5 days?

Answer 8

warfarin only has effects on coagulation factors that are being newly synthesised so it takes a few days for it to reach a therapeutic level of anticoagulation

Question 9

what drugs can be used as alternatives to warfarin?

Answer 9

DOACs

Question 10

what is the main side effect of warfarin?

Answer 10

increased risk of bleeding

Question 11

why should warfarin be avioded in patients with liver disease?

Answer 11

less able to metabolise it so they risk having too much warfarin in their system

Question 12

warfarin has a low therapeutic index, what does this mean?

Answer 12

there is a fine line between the dose needed to prevent clotting and the dose that will cause bleeding

Question 13

name some drugs that interact with warfarin and by doing so will reduce its effect making the person more susceptible to clotting

Answer 13

Rifampicin,carbamazepine (anti-epileptic),phenytoin (anti-epileptic),primidone (barbiturate anti-epileptic)

Question 14

name some CYP inhibitors that reduce the metabolism of warfarin thus increase bleeding risk

Answer 14

fluconazole, metronidazole, amiodarone, gemfibrozil and sulfamethoxazole

Question 15

how do some antibiotics cause an increase in the effects of warfarin due to their effects on gut flora?

Answer 15

some kill gut flora that synthesise vitamin K meaning there are even less clotting factors available.
especially cotrimoxazole, metronidazole, macrolides and fluoroquinolones

Question 16

name the one DOAC that doesn’t have ‘xa’ in its name

Answer 16

dabigatran

Question 17

when would you use a DOAC?

Answer 17

for secondary prevention of a VTE or as primary prevention in patients undergoing elective hip or knee replacement surgery.

Question 18

what should you check before starting warfarin?

Answer 18

electrolytes and renal function

Question 19

how are DOACs metabolised and excreted? what effect does this have on who you should avoid prescribing it to?

Answer 19

cytochorme P450 and eliminated in faeces and urine.

avoid in hepatic or renal disease.

Question 20

what is the antidote for warfarin?

Answer 20

phytomenadione (vitamin K1), prothrombin complex concentrate, fresh frozen plasma

Question 21

what is the antidote to dabigatran overdose?

Answer 21

idarucizumab