Which medication should the nurse prepare to administer for a client experiencing anaphylaxis?

The correct choice is epinephrine because it is the first-line treatment for anaphylaxis, a severe and potentially life-threatening allergic reaction. Epinephrine acts quickly to counteract the symptoms of anaphylaxis by causing vasoconstriction, increasing heart rate, and dilating the airways, which helps reduce swelling and improve breathing.

Epinephrine is typically administered intramuscularly in an emergency setting and is available in auto-injectors for patient use when they are at risk of severe allergic reactions. The swift action of epinephrine is critical, as anaphylaxis can progress rapidly and requires immediate intervention to prevent serious complications or death.

Other medications, while they may play supportive roles in managing allergic reactions, are not suitable first-line treatments for anaphylaxis. For example, dopamine and ephedrine are typically used in cases of shock or to support blood pressure rather than for treating anaphylaxis specifically. Diphenhydramine, an antihistamine, may relieve mild allergic symptoms but does not address the life-threatening effects of anaphylaxis as effectively as epinephrine, and it takes longer to work. Hence, epinephrine remains the essential medication in such critical situations.