Case report of unchanged tacrolimus clearance in a hypoxemic pediatric liver transplant recipient with hepatopulmonary syndrome

Reductions in hepatic oxygen supply may reduce the oxidative metabolism of drugs, including tacrolimus. We encountered a patient (2.3‐year‐old girl) with hypoxemia [arterial oxygen tension (PaO 2 ) 40.9 mmHg in room air] due to hepatopulmonary syndrome who had undergone living related liver transplantation. After transplantation, tacrolimus was initially administered by continuous intravenous infusion, and her PaO 2 was maintained at more than 50 mmHg [72.8 ± 10.4 (SD) mmHg] by oxygen supplementation. Apparent clearance of tacrolimus (calculated as: the infusion rate of tacrolimus/blood concentration) in the patient (0.075 1/h per kg) was comparable to those of non‐hypoxemic control pediatric cases (0.092 ± 0.014 1/h per kg, n = 7, mean age 2.2 years, PaO 2 149.2 ± 41.5 mmHg), except for the acute decline in the early period after transplantation. These findings suggest that the reduction in tacrolimus clearance is negligible when arterial oxygen tension is maintained at more than 50 mmHg, even in patients with hypoxemia.