Is it possible to reduce the dose of warfarin?
Varies from year to year, but may cause transient rise in INR. Hold warfarin x1 for single dose. Expect 25-50% warfarin dose reduction for extended course. Not always clinically significant if pt not systemically ill.
Which is longer s or are warfarin clearance?
The clearance of R-warfarin is generally half that of S-warfarin, thus as the volumes of distribution are similar, the half-life of R-warfarin is longer than that of S-warfarin. The half-life of R-warfarin ranges from 37 to 89 hours, while that of S-warfarin ranges from 21 to 43 hours.
When does the anticoagulant effect of warfarin occur?
Therapeutic doses of warfarin decrease the total amount of the active form of each vitamin K dependent clotting factor made by the liver by approximately 30% to 50%. An anticoagulation effect generally occurs within 24 hours after drug administration. However, peak anticoagulant effect may be delayed 72 to 96 hours.
How does warfarin affect phenytoin in the blood?
Additionally, warfarin may alter serum phenytoin concentrations. Expect 2- to 5-fold increase in warfarin dose requirements.
What happens if you take warfarin with rifampin?
In terms of warfarin, you may literally have to do anything from 2x to 5x the dose if your patient starts rifampin. It’s that profound. Also remember the fun little NAPLEX fact that rifampin can give your patients red-orange secretions (urine, tears, sweat).
When does the drug interaction with warfarin normalize?
Once you get the patient therapeutic and stable on phenytoin, the drug interaction should normalize out. Although warfarin interacts with everything on this lush green earth of ours, these are the interactions that really need to give you pause.
Why is warfarin used as a rodenticide for Norway rats?
Warfarin is a commonly used oral anticoagulant with anti-vitamin K activity. Warfarin therapy is associated with rare instances of idiosyncratic, clinically apparent liver injury that are usually mild and rapidly reversible on stopping. Warfarin is an odorless and colorless solid. Used as a rodenticide for Norway rats and for house mice.