Final answer:
The nurse should anticipate administering diphenhydramine to relieve the itching in the client.
Step-by-step explanation:
The drug that the nurse should anticipate to relieve the itching in a client receiving morphine by the epidural route is diphenhydramine (option a).
Diphenhydramine is an antihistamine that can help alleviate itching caused by morphine or other opioids. It works by blocking the effects of histamine, a chemical that is released during an allergic reaction and can cause itching. By blocking histamine, diphenhydramine can reduce itching in the client.
Therefore, the nurse should anticipate administering diphenhydramine to relieve the itching in the client.