Anticoagulant drugs

Question 1

How does plasma differ from serum?

Answer 1

Plasma contains clotting factors, serum does not

Question 2

What are the risk factors for a DVT?

Answer 2

Virchow's triad 
Long-haul flight
COCP
Post-op
Hospitalisation
Pregnancy
Cancer
Obesity
IV drug use

Question 3

What is Virchow’s triad?

Answer 3

Hypercoagulability
Haemodynamic changes
Endothelial injury

Question 4

What types of anticoagulants are there?

Answer 4

Warfarin
Heparin - unfractionated, LMW
DOAC
Anti-platelet drugs
Anti-fibrinolytics

Question 5

What are the pharmacodynamics of warfarin?

Answer 5

Vitamin K antagonist
Prevents gamma carboxylation of factors II, VII, IX, X
Prolongs extrinsic pathway

Question 6

What is the target INR on warfarin?

Answer 6

2. 5 for DVT, PE, AF

3. 5 for recurrent VTE or metal heart valves

Question 7

How long does warfarin take to achieve therapeutic levels?

Answer 7

At least 3 days

Question 8

What anticoagulants does warfarin inhibit?

Answer 8

Natural anti-coagulants protein C and protein S

Question 9

How do you prescribe warfarin?

Answer 9

Load with LMW heparin cover

Question 10

What drugs can potentiate warfarin?

Answer 10

Enzyme cytochrome P450 inhibitors

Carbamazepine, azathioprine, allopurinol

Question 11

What drugs can inhibit warfarin?

Answer 11

Enzyme cytochrome P450 inducers
Rifampicin
Amiodarone
Citalopram
Phenytoin

Question 12

What are the side effects of warfarin?

Answer 12

Teratogenic
Significant haemorrhage risk
Minor bleeding
Skin necrosis
Alopecia

Question 13

How can warfarin be reversed?

Answer 13

Octaplex - contains factors II, VII, IX, X
Vitamin K
Fresh frozen plasma

Question 14

How does heparin work?

Answer 14

Mucopolysaccharide that potentiates anti-thrombin

Irreversibly inactivates factors II and Xa

Question 15

Describe unfractionated heparin

Answer 15

Not often used due to inconvenience
Safe in renal failure
Safe in pregnancy

Question 16

How is unfractionated heparin prescribed?

Answer 16

Initial bolus 5000 units

Constant infusion of 1000U/hour

Question 17

How is unfractionated heparin monitored?

Answer 17

APTT

Target range of 1.5-2.5 X normal

Question 18

How can unfractionated heparin be reversed?

Answer 18

Protamine sulphate

Question 19

Describe LMW heparin

Answer 19

Convenient due to OD S.C. injections
Prescribe according to weight
Need creatinine clearance of >30ml/min

Question 20

What are the 2 classes of DOACs?

Answer 20

Direct thrombin inhibitor e.g. dabigatran

Direct factor Xa inhibitor e.g. rivaroxaban

Question 21

When can’t DOACs be used?

Answer 21

Renal failure

Mitral heart valves

Question 22

When are DOACs indicated?

Answer 22

VTE prophylaxis
Treatment of DVTs and PEs
Stroke prevention in AF

Question 23

What is the dosing of rivaroxaban?

Answer 23

15mg BD for 3 weeks then 20mg OD

Question 24

What is an alternative drug if rivaroxaban can’t be used due to renal failure?

Answer 24

Apixaban

Question 25

What is the dosing of dabigatran?

Answer 25

150mg BD | Prophylaxis dose is 110mg BD

Question 26

How can dabigatran be reversed?

Answer 26

Praxbind (Idarucizumab)

Question 27

Give examples of anti platelets

Answer 27

``` Aspirin Clopidogrel Dipyridamole Prostacyclin Glycoprotein IIb/IIIa inhibitors ```

Question 28

What type of drug is aspirin?

Answer 28

COX inhibitor

Question 29

What type of drug is clopidogrel?

Answer 29

ADP inhibitor

Question 30

How does dipyridamole work?

Answer 30

Inhibits phosphodiesterase

Question 31

How does prostacyclin work?

Answer 31

Stimulates adenylate cyclase

Question 32

Give examples of glycoprotein IIb/IIIa inhibitors?

Answer 32

Abciximab Eptifibatide Tirofiban

Question 33

What are fibrinolytic agents?

Answer 33

Thrombolytic agents used to lyse fresh thrombi by converting plasminogen to plasmin

Question 34

What genetic factors can predispose to clots?

Answer 34

Protein S deficiency Protein C deficiency Anti-thrombin deficiency Factor V leiden thrombophilia