Final answer:
For a patient with hives caused by a reaction to contrast media, antihistamines are the appropriate drug to administer as they mitigate the effects of histamines which cause itching and swelling.
Step-by-step explanation:
A patient developing hives after the injection of contrast media is likely experiencing a type of allergic reaction such as a hypersensitivity reaction. In such cases, the administration of antihistamines is a common treatment approach. Antihistamines work by preventing the histamines released by mast cells from causing the itching and swelling associated with hives. They are especially useful for mild to moderate allergic reactions. In more severe cases, such as anaphylactic shock, epinephrine is typically used as the first line of treatment, followed by antihistamines and possibly slow-acting corticosteroids to prevent late-phase reactions.
Therefore, for a patient who develops hives due to a hypersensitivity reaction to contrast media, an antihistamine would be the appropriate drug to administer, as indicated in the multiple-choice option A. Antihistamines are also used in treating other types of hypersensitivity reactions, such as type IV hypersensitivities, and can be combined with anti-inflammatory drugs or analgesics as needed.