Thrombolytic therapy is the use of drugs that dissolve blood clots. The name "thrombolytic" comes from two Greek words that mean "clot" and "loosening."
When a blood clot forms in a blood vessel, it may cut off or severely reduce blood flow to parts of the body that are served by that blood vessel. This event can cause serious damage to those parts of the body. If the clot forms in an artery that supplies blood to the heart, for example, it can cause a heart attack. A clot that cuts off blood to the brain can cause a stroke. Thrombolytic therapy is used to dissolve blood clots that could cause serious, and possibly life-threatening, damage if they are not removed. Research suggests that when used to treat stroke, thrombolytic therapy can prevent or reverse paralysis and other problems that otherwise might result.
In heart attacks, thrombolytic therapy is an alternative to stenting, a procedure in which a spring-like device is inserted into a blocked blood vessel. In general, stenting is the preferred treatment, since it both removes the clot and opens the blood vessel, which may have internal cholesterol deposits. Thrombolytic therapy only removes the clot, but it can be administered in hospitals with fewer resources than are required for insertion of a stent.
Thrombolytic therapy is also used to dissolve blood clots that form in catheters or tubes put into people's bodies for medical treatments, such as dialysis or chemotherapy.
Thrombolytic therapy uses drugs called thrombolytic agents, such as alteplase (Activase), anistreplase (Eminase), streptokinase (Streptase, Kabikinase), urokinase (Abbokinase), and tissue plasminogen activator (TPA) to dissolve clots. These drugs are given as injections, and given only under a physician's supervision.
The physician supervising thrombolytic therapy decides on the proper dose for each patient. He or she will take into account the type of drug, the purpose for which it is being used, and in some cases, the patient's weight.
For thrombolytic therapy to be effective in treating stroke or heart attack, prompt medical attention is very important. The drugs must be given within a few hours of the beginning of a stroke or heart attack. This type of treatment is not right, however, for every patient who has a heart attack or a stroke. Only a qualified medical professional can decide whether a thrombolytic agent should be used. To increase the chance of survival and reduce the risk of serious permanent damage, anyone who has signs of a heart attack or stroke should get immediate medical help.
Thrombolytic therapy may cause bleeding in other parts of the body. This side effect is usually not serious, but severe bleeding does occur in some patients, especially older people. Some people have had minor hemorrhagic strokes in which there has been a small amount of bleeding into the brain. These hemorrhagic strokes have been blocked by clots that would be broken up by use of a thrombolytic agent, so that removal of the harmful clot would cause equally dangerous bleeding. To lower the risk of serious bleeding, people who are given thrombolytic medications should move around as little as possible and should not try to get up on their own unless told to do so by a health care professional. Following all the instructions of the health care providers in charge is very important.
Thrombolytic therapy may be more likely to cause serious bleeding in people who have certain medical conditions or have recently had certain procedures. Before being given a thrombolytic agent, anyone with any of these problems or conditions should tell the physician in charge:
In addition, anyone who has had a recent streptococcal (strep) infection should tell the physician in charge. Some thrombolytic agents may not work properly in people who have just had a strep infection, so the physician may want to use a different drug.
People who take certain medicines may be at greater risk for severe bleeding when they are given a thrombolytic agent.
Women who are pregnant should tell the physician in charge before being given a thrombolytic agent. There is a slight chance that a woman who is given thrombolytic therapy during the first five months of pregnancy will have a miscarriage. Streptokinase and urokinase, however, have both been used without problems in pregnant women.
After being treated with thrombolytic therapy, women who are breastfeeding should check with their physicians before starting to breastfeed again.
Anyone who has fever or who notices bleeding or oozing from their gums, from cuts, or from the site where the thrombolytic agent was injected should immediately tell their health care provider.
People who are given thrombolytic therapy should also be alert to the signs of bleeding inside the body and should check with a physician immediately if any of the following symptoms occur:
Other side effects of thrombolytic agents are possible. Anyone who has unusual symptoms during or after thrombolytic therapy should tell a health care professional.
People who take certain medicines may be at greater risk for severe bleeding when they receive a thrombolytic agent. Anyone who is given a thrombolytic agent should tell the physician in charge about all other prescription or nonprescription (over-the-counter) medicines he or she is taking. Among the medicines that may increase the chance of bleeding are:
In addition, anyone who has been treated with anistreplase or streptokinase within the past year should tell the physician in charge. These drugs may not work properly if they are given again, so the physician may want to use a different thrombolytic agent.
Patients who are taking thrombolytic medications should not take vitamin E supplements or certain herbal preparations without consulting their doctor. High doses of vitamin E can increase the risk of hemorrhagic stroke. Ginger, borage, angelica, dong quai, feverfew, and other herbs can intensify the anticlotting effect of thrombolytic medications and increase the risk of bleeding.
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Nancy Ross-Flanigan Sam Uretsky, PharmD