The CYP2C19*17 allele is assigned as an increased function allele by CPIC. Patients carrying the CYP2C19*17 allele in combination with a normal or increased function allele may have increased metabolism of omeprazole as compared to patients with two normal function alleles. Patients carrying the CYP2C19*17 allele in combination with a no or decreased function allele may have decreased metabolism of omeprazole as compared to patients with two normal function alleles. However, conflicting evidence has been reported. This annotation only covers the pharmacokinetic relationship between CYP2C19 and omeprazole and does not include evidence about clinical outcomes. Other genetic and clinical factors may also influence metabolism of omeprazole.