Page Contents
WHAT IS e IT?
Warfarin (Coumadin) is an anticoagulant. It works to inhibit the synthesis of the following:
- Vitamin K dependent factors: factors II, VII, IX, X
- Vitamin K dependent anticoagulant proteins: protein C and protein S
WHEN DO WE USE IT?
In patients with atrial fibrillation to prevent the formation of clots.
WHEN DO WE AVOID USING IT?
During pregnancy: warfarin is known to have teratogenic effects and should not be given during pregnancy. If anticoagulation is needed then low molecular weight heparin is the drug of choice.
HOW IS IT ADMINISTERED?
WHAT ARE THE SIDE EFFECTS/TOXICITY?
ANYTHING ELSE TO KEEP IN MIND?
CYP 450 inhibitors increase the effect of Warfarin: this raises the risk of bleeding
- Acetaminophen
- NSAIDS
- Certain antibiotics/antifungals: such as metronidazole
- Amiodarone
- Cimetidine
- Thyroid hormone
- SSRIs: such as fluoxetine
- Other: cranberry juice, Ginko biloba, vitamin E
CYP 450 inducers decrease the effect of Warfarin: this raises the risk of clotting
- Neurological medications: carbamazepine, phenytoin, phenobarbital
- Supplements: Ginseng, St. John’s wort
- Oral contraceptives
- Rifampin
FURTHER READING
Page Updated: 11.01.2016