Drug Therapy: Anticoagulants Anticoagulants do not actually make
the blood thinner. These drugs prevent the blood from forming
clots, which can block arteries, veins or the valves of the
heart. Common anticoagulants are aspirin, warfarin and heparin.
Anticoagulants help reduce the risk for heart attack, stroke and
blockages in veins and arteries, such as ones caused by
phlebitis. While these types of drugs can prevent a clot from
forming, they do not have an impact on a clot that already
exists. Blood-thinning drugs are given to people who have had a
heart valve replaced or who have atrial fibrillation or
congestive heart failure. These may be given to a person who is
at risk of having a heart attack to prevent blood clots in the
arteries of the heart or to people who are at risk of a clot
forming in the heart's chambers. Certain types of drugs
(including some over-the-counter pain relievers, such as
aspirin) can combine with anticoagulants to cause an even
greater anti-clotting effect. If anticoagulants are