The CYP2D6*5 allele is assigned as a no function allele by CPIC. Patients carrying the *5 allele in combination with a normal, decreased or no function allele may have decreased imipramine dose requirements as compared to patients with alleles that result in a normal metabolizer phenotype, while patients carrying the *5 allele in combination with an increased function allele with an activity value of 3 or greater may have increased imipramine dose requirements as compared to patients with alleles that result in a normal metabolizer phenotype. Patients carrying the *5 allele in combination with an increased function allele with an activity score of 2 may have similar imipramine dose requirements as compared to patients with alleles that result in a normal metabolizer phenotype. Other genetic and clinical factors may also influence imipramine dose requirements.