Anticoagulants

Question 1

How do inducers and inhibitors of the P450 system affect INR due to warfarin metabolism?

Answer 1

Inducers: INR decreases
Inhibitors: INR increases

Question 2

Mneumonic for CYP450 inducers

Answer 2

CRAP GP’S
Carbamezapine
Rifampicin
Alcohol (chronic)
Phenytoin
Griseofulvin
Phenobarbitone
Sulphonylureas, St John’s Wart, Smoking

Question 3

Mneumonic for CYP450 inhibitors

Answer 3

SICKFACES.COM AA
Sodium valproate
Isoniazid
Cimetidine
Ketoconazole, Fluconazole
Fluoxetine, Sertaline
Alcohol (acute)+ Grapefruit juice
Chloramphenicol
Erythromycin/ Clarithromycin
Sulfonamides
Ciprofloxacin
Omeprazile
Metronidazole

Amiodarone
Allopurinol

Question 4

Describe management in a patient on warfarin with major bleeding e.g. variceal haemorrhage, intracraniail haemorrhage

Answer 4

Stop Warfarin
Give IV Vitamin K 5mg + Prothrombin complex concentrate

Question 5

If prothrombin complex concentrate is unavailable what do you give?

Answer 5

Fresh frozen plasma

Question 6

Describe management in a patient on warfarin with minor bleeding and INR >8

Answer 6

Stop Warfarin
Give IV Vitamin K 1-3mg
Repeat dose of Vitamin K if INR still too high after 24h
Restart Warfarin when INR <5

Question 7

Describe management in a patient on warfarin with INR >8 and no bleeding

Answer 7

Stop Warfarin
Give Vitamin K 1-5mg PO using the IV preparation orally
Repeat dose of Vitamin K if INR still too high after 24h
Restart Warfarin when INR <5

Question 8

Describe management in a patient on warfarin with INR 5-8 and minor bleeding

Answer 8

Stop Warfarin
Give IV Vitamin K 1-3mg
Restart Warfarin when INR <5

Question 9

Describe management in a patient on warfarin with INR 5-8 and no bleeding

Answer 9

Withhold 1-2 doses of Warfarin
Reduce subsequent maintenance dose

Question 10

What is the target INR for patients with recurrent DVT/ PE despite current anticoagulation?

Answer 10

INR 3.5

Question 11

What is the guidance for Warfarin usage in patients with bioprosthetic valves ?

Answer 11

Long term warfarin not required in absence of AF

Question 12

Patients with bioprostheses in which position should receive oral anticoagulants for the first 3 months? What target INR?

Answer 12

Mitral position
INR 2.5

Question 13

Are anticoagulants required for bioprosthetic valves in the aortic position?

Answer 13

If patient is in sinus rhythm no.
But many centres anticoagulant for 3-6 months after any tissue valve implant

Question 14

What is the MOA of fondaparinux? How is it given?

Answer 14

Activates antithrombin III
Potentiates inhibition of coagulation factors Xa
Given SC