DOAC

Question 1

DOAC - indication

Answer 1

Treatment and prevention of recurrence of VTE (secondary prevention)

Atrial Fibrillation (stroke prevention) 
based on a CHADS2-VASc score of: 

2 or greater in women
1 or greater in men

Question 2

DOAC - MOA

Answer 2

Normal mechanism of clot formation
Factor Xa converts prothrombin > thrombin
Thrombin converts fibrinogen > fibrin (clot formation)

Rivaro’Xa’ban directly inhibits factor Xa preventing conversion of
prothrombin > thrombin

Dabigatran ( direct thrombin inhibitor) prevents conversion of fibrinogen to fibrin

Question 3

DOAC - adverse effects

Answer 3

Common: Bleeding (especially epistaxis/nose bleeds, GI and genitourinary)

Other: anaemia, GI upset, dizziness, increased liver enzymes (ALT/ALP/AST/GGT)

REMEMBER BAD
Bleeding
Anaemia
Dizzy

Question 4

DOAC - interactions

Answer 4

Other antithrombotic agents (heparin, antiplatelets, NSAIDs)
Increases risk of bleeding if used with DOACs

CYP inducers/inhibitors
Affects the metabolism of DOACs

Macrolides, protease inhibitors, fluconazole
Drugs that increase the effect of DOACs but also therefore increase
adverse effects

Rifampicin and phenytoin
Drugs that decrease the effect of DOACs

Question 5

DOAC - contraindications

Answer 5

1. Active, clinically significant bleeding
   (trauma)
2. People with increased risk for major bleeding
   o Peptic ulcers
   o cancer
   o recent surgery
3. Pregnancy
4. Breastfeeding

Question 6

Warfarin vs DOAC

Answer 6

Risk of intracranial haemorrhage and major bleeding is less with DOACs compared to Warfarin - however risk of GI bleeding with DOAC is greater

Minor over use of Warfarin can increase the risk of bleeding from a minor trauma (e.g.- minor head injury) and in existing abnormalities (e.g.- peptic ulcers)

Warfarin has a low therapeutic index (the dose effective for therapy is close to the dose that causes bleeding). Therefore, small changes in hepatic warfarin metabolism by CYP enzymes can significantly change anticoagulation.

DOACs are more convenient to patient than Warfarin
Warfarin - INR measured every few days in outpatients upon starting warfarin and once a stable dosage of warfarin has been established, the INR measurement is less frequent
DOACs - do not require monitoring

Question 7

DOAC - warnings

Answer 7

Consider lowered dose or alternative medication if patient has:

Hepatic
or
Renal disease

Question 8

DOAC - examples

Answer 8

Rivaroxaban
Apixaban
Dagibatran

TAKE SAME TIME EACH DAY
Note: Rivaroxaban is the only DOAC that needs to be taken with food