Anticoagulant drugs

Question 1

Warfarin
1) Warfarin is a vitamin K antagonist - which 4 clotting factors is vitamin K important in the production of?
2) What is INR
3) What does an INR value of 1 mean?
4) What does an INR value of 2 mean?
5) Name 2 contraindications for warfarin
6) Name 2 drug interactions associated with warfarin that increases its effect
7) Name 2 drug interactions associated with warfarin that decreases its effect

Answer 1

1) Factor II, VII, IX, X
2) Measurement of how anticoagulated a patient is by warfarin. The INR is a calculation of how the prothrombin time of the patient compares with the prothrombin time of a healthy adult
3) INR of 1 = normal prothrombin time
4) INR of 2 indicates that the patient has a prothrombin time of twice a normal adult therefore it takes twice as long for blood to clot
5) Pregnancy, severe hypertension, bleeding disorders, peptic ulcers
6) Alcohol, broad spectrum antibiotics, aspirin, levothyroxine, simvastatin, NSAIDs
7) Barbiturates, carbamazepine, rifampicin

Question 2

Direct oral anticoagulants (DOACs)
1) Name a DOAC that works by inhibiting factor Xa
2) Name a DOAC that works by directly inhibiting thrombin
3) Name 2 contraindications for DOACs
4) What drug can reverse the effects of dabigatran?
5) What can be given to reverse the effects of apixapain and rivaroxaban?

Answer 2

1) Apixaban, edoxaban, fondaparinux and rivaroxaban
2) Dabigatran
3) Severe renal/liver impairment, lesions at risk of bleeding, active bleeding
4) Idarucizumab
5) Andexanet alfa

Question 3

Heparins
1) Give an example of a low molecular weight heparin
2) How do they work?
3) Name 2 side effects of both types of heparins
4) Name a contraindication for heparin
5) What can be given to reverse heparins?

Answer 3

1) Dalteparin, enoxaparin
2) Inactivates factor Xa by binding to antithrombin (endogenous inhibitor of coagulation) to increase its ability to inhibit thrombin, factor Xa and IXa
3) Bleeding, heparin induced thrombocytopenia, osteoporosis with long term use
4) Bleeding disorders, low platelets, peptic ulcers, cerebral haemorrhage, severe hypertension
5) Protamine sulphate