What is the typical duration of action for epinephrine 1:1000?

• A. 1-4 hours
• B. 4-6 hours
• C. 10-20 minutes
• D. 24 hours

Answer: (A)

Epinephrine given at 1:1000 intramuscularly for anaphylaxis typically lasts about 1 to 4 hours. This duration reflects how quickly epinephrine is absorbed, distributes, and is metabolized. It acts quickly—beta-adrenergic effects (bronchodilation, increased heart rate) and alpha-adrenergic effects (vasoconstriction) peak within minutes, but the drug is cleared relatively rapidly by metabolic enzymes in the body. Because symptoms can recur as the drug wears off, clinicians often monitor closely and may administer a second dose if needed, at short intervals (for example, every 5–15 minutes) depending on the patient’s status.