Drug Class: Vitamin K Inhibitor Flashcards

1
Q

Example of vitamin K inhibitor

A

WARFARIN

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2
Q

Mode of action of WARFARIN + conditions used in

A
  • Inhibits production of active clotting factors

Used in prevention of DVT, PE, stroke

  • In renal failure
  • Significantly obese patients
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3
Q

Side effects of WARFARIN

A

Bleeding

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4
Q

Drug-drug interactions of WARFARIN

A
  • Interaction with other drugs via CYP450
    ↑ warfarin activity
  • Aspirin, Cotrimoxazole, Trimethoprim = decrease albumin binding= ↑INR
  • Cimetidine, erythromycin= inhibit degradation by inhibiting CYP450
  • Oral antibiotics= interfere with Vit K synthesis -> decrease synthesis of clotting factors
    ↓ warfarin activity
  • Barbiturate, phenytoin, alcohol= induction of CYP450
  • Vitamin K= promote clotting factor synthesis
  • Cholestyramine= reduce absorption
    ↑↑ bleeding
  • NSAIDs/ Aspirin= inhibition of platelets/prostaglandins
  • Heparin metabolites= inhibition of clotting factors
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5
Q

Contraindications of WARFARIN

A
Narrow therapeutic range 
-	International normalised ratio (INR) 
	-	Normal INR 1 
	-	Therapeutic INR 2.5-4
Avoid in pregnancy (esp. 1st-3rd trimesters)
-	TERATOGNEIC (chondrodysplasia) 
-	Retroplacental and fetal intracerebral BLEEDING 
	-	Replace with subcutaneous/IV heparin
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