The CYP2D6*5 allele is assigned as a no function allele by CPIC. Patients carrying the *5 allele in combination with a decreased or no function allele may have an increased risk of experiencing side effects when treated with imipramine 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 2 may have a similar risk of experiencing side effects when treated with imipramine as compared to patients with alleles that result in a normal metabolizer phenotype. Other genetic and clinical factors may also influence risk of side effects when treated with imipramine.