What is the time window for administering IV tPA in acute ischemic stroke?

• A. Within 3 hours of onset
• B. Within 2 hours of onset
• C. Within 4.5 hours of onset
• D. Within 6 hours of onset

Answer: (C)

Time window for IV tPA in acute ischemic stroke is 4.5 hours from onset for eligible patients. The original trial showed benefit within 3 hours, and later studies (notably ECASS III) extended the window to 4.5 hours for carefully selected individuals who have no major contraindications and with hemorrhage ruled out on imaging. This makes 4.5 hours the best-supported cutoff for giving IV tPA. Outside this window, the balance of benefit and risk does not support routine use.