The CYP2D6*1 allele is assigned as a normal function allele by CPIC. Patients carrying the *1 allele in combination with alleles that result in a normal metabolizer phenotype may have decreased imipramine dose requirements as compared to patients carrying two increased function alleles or an increased function allele in combination with a normal function allele or a decreased function allele with an activity value of 0.5. Patients carrying the *1 allele in combination with alleles that result in a normal metabolizer phenotype may also have decreased imipramine dose requirements as compared to patients carrying an increased function allele with an activity value of 3 or greater in combination with a no function allele or a decreased function allele with an activity value of 0.25 but increased imipramine dose requirements as compared to patients with a no function allele in combination with a decreased or normal function allele or two decreased or no function alleles. Other genetic and clinical factors may also influence imipramine dose requirements.