This fact sheet
is intended to help those affected by atrial fibrillation (AF)
understand warfarin and the effects other medications may have
on the effectiveness of this therapy.
Warfarin is a medication which inhibits the clotting
process, thereby reducing the risk of AF- related stroke.
People on warfarin are required to have regular
blood tests to check for INR (international normalised ration),
a measure of the blood’s clotting capability. Warfarin works
by interfering with how the liver uses the Vitamin K taken in
our diet. Many other medications are also broken down by the liver
and they may affect how effectively warfarin thins the blood.
Medications can increase the effect of warfarin
and thus a lower dose may need to be taken, or they may decrease
the effect of warfarin so a higher dose may need to be taken.
People taking warfarin together with long-term
medications do not need to worry, but when some medications are
started, or doses are adjusted, increased monitoring of the INR
is required so that the right dose of warfarin is given and the
blood remains within INR range.