Cyclosporin A is widely used in medicine as an immunosuppressive agent. It is primarily prescribed to prevent organ rejection in patients who have undergone organ transplants, such as kidney, liver, or heart transplants. By inhibiting the activity of T-cells, it reduces the immune system's ability to attack the transplanted organ.

Additionally, it is used to treat autoimmune diseases like severe rheumatoid arthritis, psoriasis, and Crohn's disease, where it helps to control the overactive immune response that causes inflammation and tissue damage. In ophthalmology, it is applied in the form of eye drops to manage conditions like dry eye syndrome by reducing inflammation on the ocular surface.

Cyclosporin A is also being studied for its potential in treating other inflammatory and immune-related disorders, expanding its therapeutic applications. Its effectiveness in modulating the immune system makes it a critical drug in various medical fields.