Heart attacks and strokes are caused by blood clots in blood vessels supplying the heart and brain, respectively. Clot-busting medicines, also called thrombolytic agents, are drugs that are injected within the first few hours of a heart attack or stroke to break up a clot and stop the event, according to Medline Plus. There are three different kinds of clot-busters: Tissue plasminogen activator, streptokinase, and urokinase. Tissue plasminogen activator, or TPA, is the most frequently used agent. The clot-busters are effective about 75 percent of the time in breaking up a clot, says Family Practice Notebook, but there are several side effects associated with thrombolyticic drugs, some serious.
Bleeding
Family Practice Notebook reports the most common side effect of thrombolytic therapy is hemorrhage, or bleeding, occurring in up to 25 percent of patients receiving a thrombolytic agent. According to Dr. Schulman and colleagues in the June 2008 issue of "Chest," the most serious kind of post-thrombolytic hemorrhage is an intracranial hemorrhage, or bleeding inside the head, which has a 60 percent mortality rate. Other hemorrhagic complications include bleeding from the gastrointestinal tract, at the puncture site from a diagnostic catheterization and from the chest after open heart surgery. The "Chest" article lists several predisposing risks for major bleeding after receiving a thrombolytic drug including older age, uncontrolled hypertension, being underweight, and history of recent surgery or trauma.
Heart Rhythm Abnormalities
Family Practice Notebook reports that there are several types of heart rhythm disturbances often seen after thrombolytic therapy, called reperfusion arrhythmias, that are usually short-lived, do not require treatment and are a marker of successful destruction of the clot. These rhythm abnormalities are usually slow, not felt by the patient and do not cause a drop in the blood pressure.
Clot Formation
Occasionally, reports Cardiovascular Pharmacology Concepts, clots can re-form after intially dissolved by a thrombolytic agent. These new clots can actually form at sites far from the original heart attack or stroke. Usually heparin, an anticoagulant or blood thinning medication, is administered for several days after a thrombolytic agent is given to prevent the reaccumulation of clot.
