Based on the results of two large studies published in 2008, professional stroke organizations now recommend patients be treated with tissue plasminogen activator (tPA) within 4.5 hours of when stroke symptoms start (previously within 3 hours). Researchers have examined this wider treatment window for nearly 24,000 patients and found that although the risks from tPA treatment increased the longer patients waited, there were still significant benefits. Still, earlier is definitely better.
PositiveTip: if you see someone showing symptoms of a stroke, do whatever you can to get them to an emergency room for evaluation and possible treatment.