In the US the licence, or marketing authorisation, for alteplase is limited to 0-3 hours after onset of stroke, but some other countries - including the UK and Australia - have extended the licence to 4.5 hours.
In an analysis article on thebmj.com Brian Alper, vice president of evidence based medicine research and development at Dynamed, and colleagues, interpret the evidence to suggest increased mortality with uncertain benefit for its use beyond three hours.
Read their full analysis:
http://www.bmj.com/content/350/bmj.h1075
Medicine and Science from The BMJ