A 36 year-old male developed a sore throat and was treated with IM penicillin. Within 20 minutes, he felt faint and became dyspneic. Upon entry to the emergency department, he was pale and apprehensive. He had a thready pulse, and systolic blood pressure was 40 mmHg. Which of the following is the most appropriate initial agent to use?

• A. Dopamine
• B. Epinephrine
• C. Hydrocortisone
• D. Diphenhydramine

Answer: (B)

In anaphylaxis, the immediate use of epinephrine is essential because it reverses both airway and circulatory collapse. Penicillin-triggered anaphylaxis causes rapid bronchospasm, airway edema, and profound vasodilation leading to shock. Epinephrine tackles all of these at once: its alpha-1 effect constricts dilated blood vessels, reducing edema and raising blood pressure, while its beta-2 effect smooths bronchial smooth muscle to relieve bronchospasm; beta-1 support improves cardiac output. This rapid action buys critical time for airway management and further therapies.

In this patient, who became faint with dyspnea and has a systolic BP of 40 mmHg, epinephrine given promptly by intramuscular injection is the best initial step. Dosing is typically 0.3–0.5 mg of 1:1000 solution for adults, repeated as needed every 5–15 minutes, with escalation to IV epinephrine in a monitored setting if shock persists despite IM dosing. Provide airway support, oxygen, and aggressive IV fluids as part of the broader resuscitation.

Other options don’t address the acute pathophysiology quickly enough. Diphenhydramine and hydrocortisone are helpful adjuncts for some late or concurrent effects but do not rapidly reverse airway obstruction or shock. Dopamine can raise blood pressure but does not promptly relieve bronchospasm and is not the first-line treatment for anaphylaxis. Epinephrine remains the cornerstone of initial management.