A nurse is caring for a client who experiences anaphylactic shock in response to the administration of penicillin. Which of the following medications should the nurse administer first?

A. Diphenhydramine (an antihistamine) can help manage symptoms but does not reverse airway constriction or hypotension quickly enough to treat anaphylaxis. B. Epinephrine is the first-line treatment for anaphylactic shock because it rapidly reduces airway edema, increases blood pressure, and improves cardiac output. C. Albuterol may relieve bronchospasm but does not address hypotension or systemic symptoms and is secondary to epinephrine. D. Hydrocortisone helps reduce inflammation but has a delayed onset of action and is not the immediate priority in anaphylaxis.