What Is Warfarin?
Warfarin (also known as Coumadin) is an anticoagulant that works by inhibiting
Vitamin K-dependent coagulation factors.
- Theraputic doses of warfarin decrease the effects of Vitamin K-dependant
clotting factor by approximately 30% to 50%.
- An anticoagulation effect generally occurs within 24 hours after the drug
administration, though peak anticoagulant effect may be delayed 72 to 96 hours.
- The action of a single dose of warfarin
lasts 2 to 5 days, & the effects of warfarin may become more
pronounced as effects of daily doses overlap.
- The dosage & administration of warfarin is individualized for each
warfarin patient in accordance to the particular patient's PT/INR response
to the drug.
The elimination of warfarin is almost entirely by
metabolism. Warfarin is eventually metabolized to reduced metabolities (warfarin alcohols), & excreted into the
urine, & sometimes, the bile.
The objective of anticoagulation therapy is to decrease the clotting ability of
blood so that blood clot is prevented, while avoiding spontaneous bleeding.
- Numerous factors, alone or in combination including changes in diet,
medications, botanicals etc may affect patient's response to warfarin. Therefore, regular PT/INR monitoring is
- An INR of greater than 4.0 appears to provide no additional theraputic
benefit in most patients & is associated with higher risk of bleeding.
Other Observations Include:
- Elderly patients who are 60 years or older seem to exhibit greater than
expected PT/INR response to the anticoagulant effects of warfarin. Hence, a lower dose of warfarin is usually
required to produce similar therapeutic level of anticoagulation as patient age increases.
- Asian patients may require lower initiation & maintenance doses of
*Above information is extracted from Bristol-Myers Squibb website. Special thanks
to SDS, for sharing this information link.