What is the typical onset time for epinephrine to begin working?

• A. Immediately
• B. One minute
• C. Five minutes
• D. Ten minutes

Answer: (B)

The important idea here is how quickly epinephrine begins to work after it’s given by intramuscular injection for anaphylaxis. When epinephrine is absorbed from muscle, it acts rapidly on its receptors to reduce airway swelling, open the airways, and tighten blood vessels to raise blood pressure. Because the muscle is well perfused, the onset is very fast—clinical effects are typically seen within minutes, and often noticeable within about a minute or so. That’s why the answer reflects a near-immediate onset rather than a longer delay. Keep in mind that while the initial response can be quick, full stabilization may take a bit longer and may require additional dosing per protocol.