Cyclosporine

There are two types of immunosuppression: specific suppression and nonspecific suppression. In specific suppression, the blocking agent restricts the immune system from attacking one or a specific number of antigens (foreign substances). In nonspecific immunosuppression, the blocking agent prevents the immune system from attacking any antigen. Nonspecific immunosuppression, therefore, breaks down the ability of the body to defend itself against infections.

In the case of organ transplants, the recipient's body responds to the donor's organ tissues as if they were infecting foreign tissues. A drug that is a specific suppressing agent could block the immune system's antigenic response to the newly implanted organ. While specific suppression has been accomplished in animal transplants, it has not succeeded in human trials. So far, all the drugs used to suppress the immune system after an organ transplant are nonspecific suppressants.

In administering nonspecific immunosuppressants, a balance has to be maintained between the need for protecting the new organ from the immune system's attack (rejection) and the immune system's normal functioning, which protects the individual from infectious diseases. As time passes after the transplant operation, the body slowly begins to accept the new organ and the amount of immunosuppressant drugs can be decreased. If, however, the immunosuppressant is suddenly decreased shortly after the operation, larger doses may have to be given several years later to avoid rejection of the transplanted organ.

All the immunosuppressant drugs have side effects and individuals react to them in different ways. One strategy often used is to create a mix of the different drugs—usually azathioprine, cyclosporine, and prednisone—for the transplant patient. For example, a patient whose blood pressure is elevated by cyclosporine could take less of that drug and be introduced instead to prednisone. If an adverse reaction takes place with azathioprine, cyclosporine could replace it.