Patients carrying two copies of the CYP3A4*20 allele or one copy of the *20 allele in combination with one copy of the *1 allele may have increased exposure to quetiapine as compared to patients with two copies of the *1 allele. This annotation only covers the pharmacokinetic relationship between CYP3A4 and quetiapine and does not include evidence about clinical outcomes. Other genetic and clinical factors may also influence exposure to quetiapine.