Which of the following medications is a corticosteroid?

Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex and are involved in a wide range of physiological processes, including immune response regulation, stress response, and metabolism. Prednisone is a synthetic corticosteroid medication that mimics the effects of hormones produced by the adrenal glands. It is commonly used to reduce inflammation and suppress the immune system in various conditions, such as allergies, autoimmune diseases, and certain types of cancer.

In contrast, rocuronium is a neuromuscular blocker used primarily in anesthesia to provide muscle relaxation, Ambien (zolpidem) is a sedative used for the treatment of insomnia, and propofol is an anesthetic agent used for sedation during surgeries or procedures. None of these medications belong to the corticosteroid class, which is why they are not the correct answer. Prednisone's role as an anti-inflammatory and immunosuppressive agent underlines its classification as a corticosteroid, making it the accurate choice in this context.