A blood thinner, or anticoagulant, is a drug that is used to prevent blood clots from forming or to lengthen the time that it takes for blood clots to form. These drugs are often used by people who are at risk for heart attack, stroke or heart disease. There are many chemical formulations for blood thinners, and they can help prevent clotting in various ways. Those that block blood platelets from forming clots are called antiplatelet drugs. Others inhibit certain other clotting factors or the actions of a protein called thrombin, which plays a role in clotting.
The most common blood thinner is aspirin, an antiplatelet drug that has been recognized as a blood thinner since the middle of the 20th century. Often, a daily dose of aspirin is the only required cardiac medicine for people who are at risk for heart attack, stroke or heart disease. Patients who have certain medical conditions or are taking other medications should consult a healthcare professional before taking a daily dose of aspirin, because this medication could increase the risk of internal bleeding or other complications.
Conditions that might contribute to those risks include stomach ulcers, congenital blood disorders and asthma. Medications that might interact with aspirin include ibuprofin, heparin, warfarin and some antidepressants. Certain dietary supplements, such as ginkgo and fish oil, also might increase the risk of bleeding problems for someone who is taking aspirin.
Children who were born with congenital heart defects and who have undergone surgery often are prescribed a daily dose of aspirin, which helps prevent platelets from clumping together and forming clots. The use of aspirin by children must be carefully monitored and should be stopped if the child has a stomach flu, influenza or chicken pox. This is because the use of aspirin by children has been indicated in the development of Reye's syndrome, an illness that can cause damage to the major organs of the body and might be fatal.
In some cases, aspirin is not a strong enough blood thinner to address the risk of potentially life-threatening clots forming. The second most common blood thinner is warfarin. It is much stronger than aspirin, so its use must be carefully monitored. Dosing is difficult because warfarin is highly reactive. Determining the proper dosage can take several months of making adjustments and might require weekly blood tests before an ideal dose is achieved.
Patients who take warfarin and other anticoagulants are advised to monitor their intake of foods that are high in vitamin K, which can reduce the effectiveness of the drug. They also are cautioned about the risks regarding severe bleeding after bruising or cutting the skin. There is a risk of cranial bleeding if the patient incurs a head injury. Children who take warfarin are often cautioned to wear helmets when engaging in any kind of rough play.
One of the more recently developed blood thinners is clopidogrel, an antiplatelet drug. Clopidogrel is more stable than warfarin and has fewer side effects, but serious side effects — such as slurred speech, seizures, bloody vomit and severe headaches — are still possible and should be reported to a healthcare professional as soon as possible. Some patients do not metabolize clopidogrel effectively, leaving them at risk for clots.
Another type of blood thinner, heparin, is injected directly into the blood stream and inhibits the actions of thrombin. It is often used during certain types of surgery, blood transfusions and dialysis, and it might be used to help keep intravenous (IV) lines from clotting. Heparin also can slow the growth of blood clots, although — like all blood thinners — it does not dissolve clots after they have formed.
If a patient is taking any of these drugs regularly, his or her physician should be notified. Many blood thinners can interact with other drugs and reduce the effectiveness of the blood thinner or increase the risk of complications. Among the many substances that might interact with blood thinners are ibuprofen, acetaminophen and even some herbal supplements, such as ginkgo or St. John's wort. Using more than one type of blood thinner also might increase the patient's risks, although a combination might also be prescribed in certain instances.
Additionally, patients should receive directions regarding stopping the use of blood thinners before any type of surgical procedure. Physicians and dentists usually recommend stopping about a week before surgery. Stopping the use of blood thinners is indicated only if doing so does not increase the risk of heart attack or stroke, however, and it should be done only under the direction of a healthcare professional.