Short-Term Side Effects of Prednisone & Long-Term Side Effects of Prednisone Prednisone is a widely used prescription corticosteroid. It is a commonly used anti-inflammatory and immunosuppressive medication. It may be used in the treatment of conditions such as rheumatoid arthritis, severe allergic reactions, lupus, and multiple sclerosis, among other conditions. The medication is taken by mouth, either as a tablet or oral solution,1 and it is available in both immediate-release or delayed-release formulations.