Anticoagulation

Question 1

Tranexamic acid – what is it?

Answer 1

Anti-fibrinolytic drug
Oral/IV
Inhibits activation of plasminogen to plasmin (less degradation of fibrin clots)
Uses in trauma/GI bleeding/post op or delivery
CRASH 2 trail shows effective only if given in first 3-4 hours, no increase in thrombolytic events

Question 2

How does warfarin act and how is it measure?

Answer 2

Inhibits production of vit K in reduced form

Effect measured by prothrombin time (INR) – venous or capillary sample

Question 3

Drug interactions of warfarin

Answer 3

Increase effect – amox (reduce gut vit K), erythro, statins, acute alcholol intake (enz inhibition), aspirin/clop/NSAIDs (increase bleeding risk – platelet function and GI mucosal damage)

Decrease effect – rifampicin, carbamazepine, phenytoin, chronic alcohol intake (enz induction)

Question 4

What tests are useful in determining whether warfarin is indicated in AF?

Answer 4

Risk of thrombosis – CHA2DS2-VASc

Risk of bleeding – HAS-BLED

Question 5

How do DOACs work?

Answer 5

Xa inhibitors – apixaban, edoxaban, rivaroxaban

Direct thrombin inhibitors – dabigataran

Question 6

How does heparin work?

Answer 6

LMWH (longer HL of 12h) binds to and activates anti-thrombin so reducing Xa and thrombin generation
Monitored by APPT testing and dose adjustment

Question 7

Adverse effects of heparin?

Answer 7

Pain at injection site
Increased bleeding risk
Osteoporosis with prolonged use
Heparin induced thrombocytopenia – antibody mediated, 5-10 days into treatment

Question 8

How does aspirin work?

Answer 8

Causes irreversible inhibition of COX1 so less TXA2 production – less aggregation of platelets
Typically used after TIA/MI
Same effect in stroke prevention in AF but not as effective as ant-coag

Question 9

How does clopidogrel work?

Answer 9

Clopidogrel – inhibit ADP induced platelet aggregation, used with aspirin to prevent recurrent MI, used in ischaemic stroke and TIAs, increased risk of dyspepsia and GI bleeding
Effect for anti-platelets will last 5-10 days (duration of platelet lifespan)

Question 10

How do thrombolytic drugs work?

Answer 10

Increase activation of plasminogen to plasmin
tPA e.g. alteplase used for thrombolysis brain/heart/occluded venous catheters
Cause breakdown of fibrin and fibrinogen
Increase bleeding risk in hours after dose
Stenting and clot removal are alternative treatments