How long does epinephrine typically take to start working after administration?

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

Answer: (C)

Epinephrine given by the intramuscular route acts very quickly because it is absorbed rapidly into the bloodstream from the muscle rich in blood vessels. Once in circulation, it stimulates several adrenergic receptors that produce bronchodilation and vasoconstriction, reversing swelling and improving airway flow. The earliest noticeable effects often occur within about one minute, which is why EMS protocols emphasize reassessment soon after administration. While effects continue to develop over the next minutes, the fastest, observable improvement typically starts around that one-minute mark; options implying it is instantaneous or taking several minutes are less accurate for this route.