Patients carrying two copies of the CYP3A4*18 allele or one copy of the *18 allele in combination with one copy of the *1 allele may have increased metabolism of tacrolimus as compared to patients carrying two copies of the *1 allele. This annotation only covers the pharmacokinetic relationship between CYP3A4 and tacrolimus and does not include evidence about clinical outcomes. Other genetic and clinical factors may also influence tacrolimus metabolism.