the maximum window of time a fibrinolytic can be administered​ is
Reperfusion therapy Thrombolytic therapy is indicated for the treatment of STEMI – if it can begin within 12 hours of the onset of symptoms, and the person is eligible based on exclusion criteria, and a coronary angioplasty is not immediately available.[4] Thrombolysis is most effective in the first 2 hours. After 12 hours, the risk of intracranial bleeding associated with thrombolytic therapy outweighs any benefit.[2][5][6] Because irreversible injury occurs within 2–4 hours of the infarction, there is a limited window of time available for reperfusion to work.