Use of Tacrolimus Blood-bile Ratio for the Detection of Early Liver Failure After Liver Transplantation

Tacrolimus is the most widely used immunosuppressive drug in the prevention of rejection after solid organ transplantation. Pharmacokinetic studies in healthy volunteers and in transplanted patients have shown that this molecule is rapidly absorbed after oral administration (maximum plasma concentration after 1-2 hours), is found in the circulation bound mainly to erythrocytes and, after being metabolized by CYP3A4, is eliminated through the bile. The importance of the tacrolimus blood dosage is now widely recognized for detecting the immunosuppressive capacity reached in the individual patient or the eventual overdose of the drug. In the use of Tacrolimus after Liver Transplantation, however, it is interesting to note that the biochemical pathway for metabolism and excretion of the drug is present in the transplanted organ, the main object of immunological and functional surveillance. The excretory capacity of Tacrolimus by the liver through the bile, therefore, could be a useful tool for recognizing the early liver failure from a functional point of view, before the onset of hepatoecrosis.