List of products in the National Drug Code with proprietary name . Dexamethasone is used to treat conditions such as arthritis, blood/hormone disorders, allergic reactions, skin diseases, eye problems, breathing problems, bowel disorders, cancer, and immune system disorders. It is also used as a test for an adrenal gland disorder (Cushing's syndrome). Dexamethasone belongs to a class of drugs known as corticosteroids. It decreases your immune system's response to various diseases to reduce symptoms such as swelling and allergic-type reactions. This injectable form of dexamethasone is used when a similar drug cannot be taken by mouth or when a very fast response is needed, especially in patients with severe medical conditions. Talk to your doctor about the risks and benefits of dexamethasone, especially if it is to be injected near your spine (epidural). Rare but serious side effects may occur with epidural use.