Dexamethasone (Decadron®) is a steroid. It has a number of different uses including asthma, arthritis, some autoimmune diseases, and leukemia. It is also used to prevent nausea and vomiting associated with chemotherapy. Because it is used to treat a variety of disorders, make sure you ask your child's doctor about why dexamethasone is being prescribed for your child. Dexamethasone is available as a tablet, injection, liquid, eye ointment, or eye-drop.