The purpose of this study is to evaluate if concentration of tacrolimus metabolites is increased in patients presenting tacrolimus (TAC) side effects.

The study will evaluate whether the blood concentration of TAC metabolites (13-O-desmethyl-tacrolimus, 15-O-desmethyl-tacrolimus and 31-O-desmethyl-tacrolimus), measured between Day1 and Day5 of its introduction, is increased in patients with TAC toxicity.

A blood test will be performed daily from Day1 to Day5 for the measurement of TAC concentration and TAC metabolites concentration.

Inclusion Criteria:

• Adult patients (> 18 years) of both sexes,
• Candidates for liver transplantation or retransplantation, whatever the etiology and severity of the underlying disease,
• Not having expressed their opposition to participation in the study

Exclusion Criteria:

• Associated transplantation of another organ
• Contraindications to TAC administration
• Delayed introduction of TAC (beyond the 5th postoperative day) whatever the cause.

Liver transplant patients