Common treatments for myosistis include immunosuppressants. These powerful drugs inhibit the immune system, reducing its ability to attack infections and, in people with autoimmune diseases, its ability to attack healthy tissue.

The most commonly used immunosuppressants are methotrexate (Rheumatrex®, Folex®) and azathioprine (Imuran®).

Possible side effects with these drugs include upset stomach, diarrhea, loss of appetite, mouth sores, hair loss, rashes, chills and fever.