Final answer:
The nurse should inform the physician about the client's hypersensitivity to epinephrine and collaborate on selecting an alternative medication.
Step-by-step explanation:
The best response by the nurse in this situation would be option 2: "I will let the physician know about this immediately; we will need to choose an alternative medication."
Epinephrine is the first-line treatment for severe allergic reactions, including anaphylaxis, as it can counteract the drop in blood pressure and relax bronchial smooth muscle. However, if the client has a known hypersensitivity to epinephrine, an alternative medication will need to be used to treat the allergic reaction. The nurse should inform the physician and collaborate on selecting a different medication that is safe for the client to administer.