The SLCO1B1*1 allele is assigned as a normal function allele by CPIC. Patients carrying SLCO1B1*1 allele in combination with another normal function allele may have decreased simvastatin acid concentration when treated with simvastatin as compared to patients with a no function allele in combination with a normal or increased function allele or with two no function alleles. Other genetic and clinical factors may also influence the metabolism of simvastatin. This annotation only covers the pharmacokinetic relationship between SLCO1B1 and simvastatin acid or simvastatin and does not include evidence about clinical outcomes.