A nurse is preparing to administer erythromycin PO to a client who has an infection. The nurse checks the client's medical record and notes that the client has a severe allergy to penicillin. Which of the following actions should the nurse take?

A. There is no need for change of antibiotic as there is no cross-rectivity between macrolides and penicillins. B. Given the client's severe allergy to penicillin, it would be safe to administer erythromycin, a macrolide, as there is no risk of cross-reactivity. C. Diphenhydramine is an antihistamine commonly used to treat allergic reactions, but premedicating the client with diphenhydramine is not necessary. D. Changing the route of administration would not alter the risk of an allergic reaction.