Warfarin Flashcards
Explain the route of Warfarin in the body
oral route—> binds to plasma proteins(albumin)—> excreted in urine and stool
What is warfarin used for
recurrence of acute deep vein thrombosis leading to pulmonary embolism even while heparin
What types of surgery should you take warfarin to prevent venous thromboembolism
orthopedic and gynecological surgery
What is warfarin used to protect against
patients with acute MI, prosthetic heart valves and chronic atrial fibrillation
what does vitamin K epioxide normally do
posttranscriptional carboxylation of factors 2, 7, 9, and 10 and the anticoagulant proteins C and S.
What are the side effects of warfarin
bleedings, especially internal bleeding
skin lesions and skin necrosis
purple toe syndrome
many drug interactions
How soon after starting warfarin treat can you see skin lesions/ necrosis. How common is it and who develops
its rare; usually happens 3-10 days after therapy initiation; primarily women
What is purple toe syndrome
its painful, blue tinge discoloration- due to cholesterol emboli breaking from plaques
When purple syndrome does occur, how soon after treatment does it occur
it happens 3-8 after therapy begins
explain how Warfarin interacts with aspirin and phenylbutazone
aspirin and phenylbutazone (NSAID) removes warfarin from albumin—increases bleeding and decreases platelet aggregation
How do antibiotics and warfarin interact with each other
decrease microbial vitamin K production–no competition and doesn’t stop Warfarin from working
How do oral contraceptives and warfarin interacts together
oral contraceptives decrease warfarin effectiveness by increasing plasma clotting factors and decreasing antithrombin III–no point
How do barbiturates and rifampin interact with warfarin
it induces microsomal P450 system and breaks down Warfarin faster
What is the half life of warfarin
its about 40 hours but varies (kind of like heparin) but its variable among individuals
Can Warfarin be given to pregnant women
NO
What effect will warfarin have on pregnant women; what dose should be given
Warfarin crosses the placenta and causes fetal hemorrhage and malformation; TEROGENIC
don’t give any time of dose…instead give heparin or lmwh
What is the half life of factor 7
6 hours
What is the half life of factor 9
24 hours
What is the half life of factor 10
40 hours
What is the half life of factor 2 (prothrombin)
60 hours
What does time Warfarin action depend on
it depends on the disappearance of factors 2, 7, 9, 10
How fast does Warfarin work
anticoagulant effects can usually be seen in 24 hours but peak may take 72-96 hours (3-5 days) because pool of clotting factors have to decrease
Which drugs can interact and decrease anticoagulant effects of warfarin
- estrogen-increases clotting factors
- phenytoin-increases metabolism
- rifampin -increase metabolism
- baribiturates
- vitamin K-completes with warfarin
What drugs increase the bleeding tendencies of Warfarin
- cephalosporins-decrease vitamin K
- salicyclates-
- adrenal corticosteroids
- NSAIDS-remove warfarin from albumin
