Temporary Parenteral Tacrolimus Requirement due to Unexplained Low Through Levels in a Liver Transplant Patient with Short Bowel Syndrome

An adequate level of tacrolimus in serum should be obtained to prevent acute rejection following liver transplantation. Because of good gastrointestinal absorption of oral tacrolimus, adequate trough levels can be achieved even in patients with short bowel syndrome. Rarely, adequate through levels cannot be obtained by oral administration of the drug for several reasons such as inadequate absorption, having a discordant patient, laboratory error, and/or interactions with other drugs and foods. Here, we described a 16-year-old patient who had undergone massive intestinal resection due to mesenteric torsion 5 years previously and required liver transplantation for cryptogenic cirrhosis. Her remnant small bowel length was 90 cm. After a successful living donor liver transplantation, oral tacrolimus administration resulted in inadequate through levels in some parts of the postoperative period. We checked up all the potential reasons but could not identify any cause. An intravenous tacrolimus including immunosuppressive regimen was temporarily required. She maintained adequate blood levels of tacrolimus by parenteral route for a while; thereafter, oral administration resulted in enough blood drug levels. She was discharged with oral tacrolimus therapy. We concluded that very rarely, adequate blood levels of tacrolimus cannot be achieved by oral administration for unexplained reasons. In such cases, temporary administration of parenteral tacrolimus can be life-saving.