The CYP2C19*9 allele is assigned as a decreased function allele by CPIC. Patients carrying the CYP2C19*9 allele in combination with a no, decreased, normal, or increased function allele may have decreased metabolism of lansoprazole as compared to patients with two normal function alleles. This annotation only covers the pharmacokinetic relationship between CYP2C19 and lansoprazole and does not include evidence about clinical outcomes. Other genetic and clinical factors may also influence metabolism of lansoprazole.