Pharmacology I Flashcards
What is the mechanism of action of warfarin?
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
What do anticoagulants target in the coagulation cascade?
Block activation of fibrin polymerization and secondary homeostasis
What is the main CYP enzyme responsible for metabolism of warfarin?
CYP2C9
Why is response towards warfarin highly interindividual variable?
Genetic polymorphism of CYP2C9 and VKORC1 requires monitoring of INR and PT
What are some ADRs associated with warfarin?
Hemorrhage / Bleeding
Hepatitis
Cutaneous necrosis and infarction of buttocks, breast and extremities
Which groups of patients are at risk of developing hepatitis from warfarin?
Those > 60 years old, male and on warfarin for less than a month
What are some absolute contraindications related to warfarin?
Hypersensitivity
Active bleeding
Pregnancy
Severe hypertension
Severe renal or hepatic disease
Subacute bacterial endocarditis
After recent major surgery
What are some relative contraindications related to warfarin?
Breastfeeding
Colitis
Mild / moderate hypertension
Mild/ moderate renal or hepatic disease
Drainage tubes in any orifice
What are some DDI to be of concern when on warfarin?
Increase bleeding risk: Paracetamol, NSAIDs, salicylates, PPI, metronidazole
Decreased efficacy: Barbiturates, corticosteroids, spirinolactones, thiazide diuretics
What are some drug food interactions to be of concern when on warfarin?
Increased bleeding risk: Gingko, ginseng, reishi mushroom, cranberry juice, alcohol
Decreased efficacy: Vitamin K supplements, green tea