Anticoagulants

Question 1

What are the main types of anticoagulants?

Answer 1

Heparin
Warfarin
DOACs

Question 2

What is the indication of heparin?

Answer 2

1. VTE - prophylaxis and rx

2. ACS

Question 3

What are the two types of heparin?

Answer 3

1. LMWH

2. Unfractionated heparin.

Question 4

What are examples of LMWH?

Answer 4

Dalteparin
Enoxaparin
Tinzaparin

Question 5

Give the mechanism of action of heparin

Answer 5

inhibit function of thrombin and factor Xa which are key to formation of fibrin clot

Question 6

How does unfractionated heparin work?

Answer 6

Binds antithrombin, increases ability to inhibit thrombin, factor Xa and IXa

Question 7

How does LMWH work?

Answer 7

similar to UFH but preferentially inhibit factor Xa

Question 8

Why is LMWH generally preferred to UFH?

Answer 8

• response is more predictable
• lab monitoring not required
• only needs to be given OD or BD

Question 9

what are SEs of heparin?

Answer 9

• ↑ bleeding
• heparin induced thrombocytopenia (mainly UFH)
• osteoporosis (long term)
• hyperkalaemia (beware)

Question 10

What are the CIs of heparin?

Answer 10

1. Bleeding disorders
2. Platelets <60
3. Previous HIT
4. Peptic ulcer
5. Cerebral haemorrhage
6. Severe HTN
7. Neurosurgery

Question 11

When should LMWH be used at a lower dose and why?

Answer 11

renal impairment
may accumulate
(can use UFH instead)

Question 12

What drug is similar to heparin and what does it act on?

Answer 12

fondaparinux

inhibits factor Xa only

Question 13

What is the indication of fondaparinux?

Answer 13

VTE prophylaxis
Rx of unstable angina and NSTEMI/STEMI - ACS
Rx of DVT + PE

Question 14

How is UFH administered

Answer 14

IV

Question 15

How is LMWH administered?

Answer 15

SC

Question 16

When is UFH more useful?

Answer 16

1. Situations where there is a high risk of bleeding as anticoagulation can be terminated rapidly
2. Renal failure

Question 17

What is an antidote for heparin?

Answer 17

protamine sulphate

Question 18

How does warfarin work?

Answer 18

Inhibits vitamin K epoxide reductase preventing reactivation of vitamin K and coagulation factor synthesis
Clotting factors II, VII, IX, X (1972) + protein C

Question 19

What are the indications of warfarin?

Answer 19

1. VTE - prevent clot extension + recurrence
2. AF
3. Prevent heart valve replacement complications

Question 20

What is warfarin NOT used for? Why?

Answer 20

to prevent arterial thrombosis e.g. MI, thrombotic stroke

This is driven by platelet aggregation so is prevented by anti platelets e.g. aspirin, clopidogrel

Question 21

When is the target INR 2.5-3?

Answer 21

VTE
AF
Cardioversion
Antiphospholipid syndrome

Question 22

When is target INR 3.5?

Answer 22

recurrent VTE whilst on anticoagulants

Question 23

What is INR?

Answer 23

Ratio of prothrombin time for the patient over the normal prothrombin time

Question 24

What factors make warfarin more active?

Answer 24

Liver disease
P450 enzyme inhibitors - amiodarone, ciprofloxacin
Cranberry juice

Question 25

What are SEs of warfarin?

Answer 25

``` Bleeding e.g. with peptic ulcers, minor trauma Skin necrosis (rare) ```

Question 26

What factors increase risk of bleeding in those on warfarin?

Answer 26

Those at increased risk of haemorrhage: - >65yrs - Prev. bleeding episode - Recent ischaemic stroke, HTN etc - Regular NSAIDs - XS alcohol, falls - Recent or imminent surgery, trauma

Question 27

How is warfarin administered?

Answer 27

orally

Question 28

What INR indicates increased bleeding risk?

Answer 28

increased INR

Question 29

What test measures how well the coagulation factors in the extrinsic pathway work?

Answer 29

PT

Question 30

What test measures the clotting factors of the intrinsic and common pathways?

Answer 30

PTT

Question 31

What is PT?

Answer 31

Prothrombin time | measures number of seconds it takes for a clot to form

Question 32

What is PTT

Answer 32

Partial thromboplastin time (aPTT), partial as absence of tissue factor

Question 33

What is INR?

Answer 33

calculation that adjusts for changes in the PT reagents and allows for results from different labs to be compared

Question 34

When should target INR be higher?

Answer 34

if there is a higher risk of a blood clot

Question 35

What is the management of major bleeding on warfarin?

Answer 35

1. Stop warfarin 2. Give IV vit K 5mg 3. Prothrombin complex concentrate

Question 36

What is the management of minor bleeding with an INR >8

Answer 36

stop warfarin IV vit K 1-3mg Restart warfarin when INR <5

Question 37

What is the management of INR >8 w no bleeding

Answer 37

Stop warfarin Vit K 1-5mg PO Restart warfarin when INR <5

Question 38

What is the management of INR 5-8 w minor bleeding?

Answer 38

same as >8 w minor bleeding

Question 39

What is the management of INR 5-8 w no bleeding?

Answer 39

withhold 1 or 2 doses of warfarin | reduce subsequent maintenance dose

Question 40

What things can lower INR (increase risk of clotting)

Answer 40

P450 inducers: - AEDs - barbiturates - rifampicin - chronic alcohol - St Johns Wort - Smoking

Question 41

What things can increase INR (increase risk of bleeding)

Answer 41

P450 inhibitors: (decrease W metabolism) - abx: ciprofloxacin, erythromycin (macrolide) - fluconazole - isoniazid - protease inhibitors - omeprazole

Question 42

What are rivaroxaban and apixaban examples of? how do they work?

Answer 42

Direct oral anticoagulants (DOAC) | factor Xa inhibitors, in the NAME lol

Question 43

How does dabigatran work? what is it an example of?

Answer 43

DOAC | direct thrombin inhibitor

Question 44

What is the administration route of DOAC?

Answer 44

oral

Question 45

What are DOACs used for?

Answer 45

Alternative to warfarin 1. prevention of VTE following hip/knee surgery 2. Rx of DVT/PE 3. prevention of stroke in non-valvular AF

Question 46

How should warfarin be given initially?

Answer 46

5-10mg given at 18:00 on days 1 and 2 Check INR on day 3 Adjust subsequent doses according to INR