Cyclosporine is an immunosuppressive medication primarily used to prevent organ rejection in transplant patients. It works by inhibiting the activity of certain immune cells, which helps the body accept the new organ without attacking it. In addition to its use in transplants, cyclosporine is also prescribed for autoimmune conditions like rheumatoid arthritis and psoriasis. It is usually taken orally or given as an injection, and patients must be monitored for potential side effects, including kidney damage and increased risk of infections.