An anticoagulant is
a substance that prevents coagulation (clotting)
of blood.
Anticoagulants reduce
blood clotting. This assists in preventing deep vein thrombosis, pulmonary
embolism, heart attack and stroke.
Warfarin is a prominent
member of the class of anticoagulants derived from coumarin,
which is found in many plants. It takes at least 48 to 72 hours for
the anticoagulant effect of warfarin to develop. Where an immediate effect
is required, heparin must
be given concomitantly. These anticoagulants are used to treat patients
with deep-vein thrombosis (DVT), pulmonary embolism (PE), atrial fibrillation (AF), and mechanical prosthetic heart valves.
Coagulation of blood is a
very intricate matter, and is well outside the bounds of
this site
-for those
interested, a good start is the information at
In the coagulation of
blood, Vitamin K (a group of fat-soluble vitamins) plays
an important role.
Warfarin works by
blocking recycling of vitamin K, so that the body and tissues have lower levels
of active vitamin K, and thus a reduced tendency for clots to
form.
Any supplemental vitamin
K reverses the vitamin K deficiency caused by warfarin, and therefore
reduces or totally reverses the intended anticoagulant action of warfarin
and related drugs.
Foods containing high
amounts of vitamin K (green leafy vegetables) are avoided when taking warfarin.
So, the proper
anticoagulant action of the drug is a function of vitamin K intake and drugdose,
and (due to differing absorption) must be individualized for each patient. The
action of warfarin and vitamin K both require two to five days after
dosing to have maximum effect, and neither warfarin
nor vitamin K shows much effect in the first 24 hours after they
are given.
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