Anticoagulants

Question 1

what are the 2 drugs that decrease INR in patients who are on warfarin (drug drug interactions)

Answer 1

Rifampicin and St John’s wort

Question 2

what clotting factors does warfarin block the production of?

Answer 2

2,7,9,10 protein C and protein S

Question 3

Describe anti-platelet drugs. Give examples of anti-platelet drugs

Answer 3

Antiplatelet drugs decrease platelet aggregation and inhibit thrombus formation predominantly in the arterial circulation.
• Aspirin
• Phenopuridines (clopidogrel)
Glycoprotein 2b and 3a inhibitors

Question 4

what CHADS2 score is needed for a patient to be put on anticoagulants?

Answer 4

CHADS2 score > 1

Question 5

what are some side effects of heparin?

Answer 5

thrombocytopenia, osteoporosis, allergy and HIT (an autoimmune reaction)

Question 6

in the acute setting of warfarin overdose and very high INR level, what do we administer?

Answer 6

Fresh frozen plasma, vitamin K and prothrombinex

Question 7

what drug would you NOT co-prescribe with warfarin?

Answer 7

NSAIDS. These medications cannot only inhibit platelet function, they also can cause GI ulceration, and some also interfere with warfarin clearance

Question 8

When is dabigatran contraindicated?

Answer 8

Dabigatran is contraindicated in patients with creatinine clearance less than 30mL/min

Question 9

other than for AF patients, when would warfarin be commonly prescribed?

Answer 9

Clots elsewhere in the body- e.g. venous sinus thrombosis, PE etc.

Question 10

what fruit juice can’t you use warfarin?

Answer 10

cranberry

Question 11

how does rifampicin interfere with anticoagulants like warfarin?

Answer 11

induces hepatic cytochromes that metabolise warfarin

Question 12

how is clexane (LMWH) cleared by the body?

Answer 12

renally cleared. so need to watch creatinine

Question 13

how to reverse unfractionated heparin?

Answer 13

protamine sulfate

Question 14

Mr Jones presents for an elective total hip replacement operation. He is an otherwise well 77-year-old man. What would you prescribe for VTE prophylaxis?

Answer 14

Apixaban/ rivaroxaban/ dabigatran

and LMWH

Question 15

Mr Jung presents for an elective hip replacement operation. He is an otherwise well 77-year-old man but has a creatinine clearance of 20 mL/min due to a history of polycystic kidneys. What would you prescribe for VTE prophylaxis?

Answer 15

Reduced dose of rivaroxaban
+
20 mg enoxaparin daily