What is the first-line treatment for anaphylaxis?

• A. Intramuscular epinephrine.
• B. Diphenhydramine.
• C. Albuterol.
• D. Hydrocortisone.

Answer: (A)

Anaphylaxis is a medical emergency requiring immediate reversal of airway, breathing, and circulation problems. Epinephrine given by intramuscular injection acts quickly on multiple receptors to stop the reaction from progressing: alpha-1 effects constrict swollen vessels to raise blood pressure and reduce mucosal edema, beta-1 effects boost heart rate and contractility to support circulation, and beta-2 effects relax bronchi and help open the airway. This combination rapidly improves breathing, reduces swelling, and stabilizes blood pressure, which is why it’s the first treatment you give right away.

The intramuscular route in the mid-outer thigh is chosen because it delivers epinephrine fastest and most reliably in an emergency. Dosing is typically 0.3 to 0.5 mg of a 1:1000 solution for adults, with repeated doses every 5 to 15 minutes as needed while symptoms improve. Pediatric dosing is weight-based but uses the same principle and aims to deliver a prompt, repeatable dose.

Other options are not first-line because they do not stop the life-threatening airway compromise and shock as quickly. Diphenhydramine and hydrocortisone may be used later as adjuncts, but they do not reverse airway obstruction or hypotension promptly. Albuterol can help with bronchospasm but won’t address the vascular collapse or swelling driving the symptoms, and relying on it alone risks deterioration. After the initial epinephrine, ongoing monitoring, airway support, and seeking emergency care are essential due to the risk of biphasic or delayed reactions.