Pharmacology of Immunosuppressants Following Heart Transplantation

The ongoing success of transplantation is largely due to the development of drugs to stop the patient's body from rejecting the new organ. In addition to steroids, two main types of drug are used to suppress the immune system following heart transplantation: calcineurin inhibitors (Ciclosporin-A or Tacrolimus) and mycophenolate. However, different patients respond in different ways to these drugs, with the same dose leading to different levels of the drug in the blood. This varies due to genetic and other factors such as age, kidney function and the use of other drugs. Therefore, the levels of immunosuppressive drugs in the blood are routinely measured and the dose adjusted accordingly. However, some patients still experience episodes of rejection despite apparently acceptable levels. In this study, the investigators will measure levels of the drugs (in the blood, in a type of white blood cell called T-cells and in the heart muscle) and the effectiveness of the drugs on T-cells. The investigators will compare these levels with patient genetic factors and the amount of rejection measured on heart biopsies. This will enable us to better understand how the blood and tissue levels of these drugs change with genetic and other factors in order to optimise immunosuppressive therapy and further improve outcomes from heart transplantation.