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 a lower risk of lovastatin-related myopathy when treated with lovastatin 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 toxicity of simvastatin.