Thrombolytics & t-PA
In the case of ischemic stroke, a thrombolytic drug is administered intravenously to help dissolve blood clots in arteries and reestablish blood flow to the brain. A stroke is a dynamic process that typically kills 2 million nerve cells per minute over approximately eight hours. When the thrombolytic drug is administered, it can interrupt the stroke and prevent loss of more nerve cells.
Our bodies produce tissue plasminogen activator (t-PA), an enzyme that changes the plasminogen in our bodies into another enzyme, which dissolves blood clots. The first enginered thrombolytic for stroke treatment was approved by the Food & Drug Administration in 1996. That thrombolytic is a man-made enzyme called tissue plasminogen activator (t-PA) — an enzyme that changes or activates plasminogen in the human body into another enzyme that can dissolve a blood clot.
T-PA has been genetically engineered so that it can also be administered intravenously to dissolve the very serious clots associated with stroke. It is available in most hospital emergency departments throughout the United States and is approved for qualifying patients who arrive at the hospital within three hours of symptom onset.
This three-hour window was set because initial t-PA trials revealed that the drug is most effective when administered within three hours of the onset of symptoms. In terms of stroke outcomes at three months, the administration of the thrombolytic drug at one hour after stroke symptom onset is 3.5 times more effective than administration at three hours after symptom onset. Earlier administration is better. The the primary goal remains to be prompt administration of IV t-PA to appropriate patients as soon as possible after the onset of symptoms.
A current international study is beginning to produce evidence that t-PA may also be effective up to 4.5 hours after the onset of symptoms — another potential advancement in stroke treatment. Because that window for successful treatment might be widening from a research perspective does not mean you can take your time getting to the hospital if you are experiencing stroke symptoms. The faster you get treatment for stroke the better your chances of a full recovery will always hold true.