A nurse is caring for a client who has urticaria following administration of an antibiotic. Which of the following medications should the nurse prepare to administer?

Rationale: A. Protamine: Protamine is used to reverse the effects of heparin, particularly in cases of heparin overdose or to stop excessive bleeding. It does not treat allergic reactions like urticaria. B. Naloxone: Naloxone is an opioid antagonist used to reverse opioid-induced respiratory depression or overdose. It has no effect on histamine-mediated symptoms such as urticaria. C. Hydralazine: Hydralazine is an antihypertensive medication that lowers blood pressure by relaxing arterial smooth muscle. It is not appropriate for managing allergic skin reactions. D. Diphenhydramine: Diphenhydramine is an antihistamine that blocks histamine receptors, making it effective for treating allergic reactions such as urticaria (hives). It reduces itching, swelling, and redness caused by histamine release.