This learning resource was developed by Medline Plus. Strokes can be caused by blood clots that travel to a blood vessel in the brain which can block blood flow to that area. These strokes are known as an ischemic stroke. Thrombolytics can be used to help dissolve the clot quickly. Transfusing thrombolytics within 3 hours of the first stroke symptoms can help limit stroke damage and disability. Thrombolytics may not be given if the patient suffers from a recent head injury, bleeding problems, bleeding ulcers,pregnancy, surgery, taken blood thinning medications such as Coumadin, trauma, and uncontrolled high blood pressure. The major risk of receiving thrombolytic therapy (TPA) is hemorrhage.