Two- to three-fold increase in blood tacrolimus (FK506) levels during diarrhea in liver-transplanted children

Background: The diagnosis and treatment of diarrhea in liver transplant recipients often pose a challenge owing to the variety of infectious and non-infectious causes. However, diagnosis is principally focused on ruling out an infectious etiology. Tacrolimus, an immunosuppressive agent generally used after liver transplantation, is absorbed mainly from the duodenum through the upper jejunum. It can be assumed that metabolism of the drug will be influenced by diarrhea. Methods: Four liver transplant recipients who developed an episode of acute gastroenteritis. Infectious etiology was confirmed; trough tacrolimus levels were measured before, during and after gastroenteritis. Results: All patients presented a two- to three-fold increase in blood tacrolimus levels after the onset of gastroenteritis. Conclusions: Until the role played by the intestine in the metabolism of tacrolimus is fully understood, it is prudent to recommend early dose reduction of tacrolimus and careful monitoring of trough levels during diarrheal disorders of any nature in pediatric liver-transplanted patients.