Patients with two copies of the CYP3A4*1 allele may have decreased exposure to quetiapine as compared to patients with two copies of the *20 or *22 alleles or one copy of the *1 allele in combination with one copy of the *20 or *22 alleles. 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.