Following heart transplantation many patients develop acute renal failure in the early posttransplant phase and some are in need of renal replacement therapy for shorter or longer time. The cause of this acute renal failure is most probably multi factorial but many reports indicate that cyclosporine has a central role in the pathophysiology and it is generally recommended to lower the cyclosporine load to patients developing acute renal failure in this population.

Several in vitro studies on renal cells in culture indicate that the primary metabolites of cyclosporine (AM1, AM9, AM4N) are less toxic to the kidney than cyclosporine itself. However, the secondary metabolite AM19 as well as the cyclic metabolites AM1c and AM1c9 has been associated with decreased renal function and nephrotoxicity renal transplant recipients.

The primary objective of this pilot study is to investigate if the concentrations of secondary- and cyclic metabolites of cyclosporine (AM19, AM1c, AM1c9) is related to development of acute renal failure in the early posttransplant phase following heart transplantation.

Secondary objectives are to investigate associations between genotypes of P-glycoprotein and CYP3A5 and the metabolic pattern of cyclosporine.

Inclusion Criteria:

• Heart transplant recipients receiving CsA as part of their immunosuppressive therapy.
• 18 years of age or older.
• Signed informed consent.

Exclusion Criteria:

• None