Pharmacology I Flashcards

1
Q

What is the mechanism of action of warfarin?

A

Inhibit vitamin K reductase enzymes that reduces inactive Vit K to active form

Decrease vitamin K dependent coagulation factor II, VII, IX and X as they require active vit K

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2
Q

What do anticoagulants target in the coagulation cascade?

A

Block activation of fibrin polymerization and secondary homeostasis

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3
Q

What is the main CYP enzyme responsible for metabolism of warfarin?

A

CYP2C9

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4
Q

Why is response towards warfarin highly interindividual variable?

A

Genetic polymorphism of CYP2C9 and VKORC1 requires monitoring of INR and PT

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5
Q

What are some ADRs associated with warfarin?

A

Hemorrhage / Bleeding

Hepatitis

Cutaneous necrosis and infarction of buttocks, breast and extremities

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6
Q

Which groups of patients are at risk of developing hepatitis from warfarin?

A

Those > 60 years old, male and on warfarin for less than a month

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7
Q

What are some absolute contraindications related to warfarin?

A

Hypersensitivity
Active bleeding
Pregnancy
Severe hypertension
Severe renal or hepatic disease
Subacute bacterial endocarditis
After recent major surgery

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8
Q

What are some relative contraindications related to warfarin?

A

Breastfeeding
Colitis
Mild / moderate hypertension
Mild/ moderate renal or hepatic disease
Drainage tubes in any orifice

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9
Q

What are some DDI to be of concern when on warfarin?

A

Increase bleeding risk: Paracetamol, NSAIDs, salicylates, PPI, metronidazole

Decreased efficacy: Barbiturates, corticosteroids, spirinolactones, thiazide diuretics

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10
Q

What are some drug food interactions to be of concern when on warfarin?

A

Increased bleeding risk: Gingko, ginseng, reishi mushroom, cranberry juice, alcohol

Decreased efficacy: Vitamin K supplements, green tea

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