CYP2D6 Genotyping

Using a QIAamp DNA Blood Mini Kit (Qiagen, Tokyo, Japan), DNA was extracted from 2 mL of venous blood that was collected in a blood collection tube containing ethylenediaminetetraacetic acid–2Na. To detect CYP2D6‐mutated alleles, direct sequencing and polymerase chain reaction–restriction fragment length polymorphism (PCR‐RFLP), for *2, *4, *10, *14A, *14B, *18, *21, and *41, and long‐PCR methods (for *5 gene‐deleted) were performed. An allele without any variants was determined as *1. Metabolic activity was defined as the normal alleles *1 and *2, the decreased‐activity alleles *10 and *41, the inactive alleles *4, *5, and *14A, and the unknown‐activity alleles *14B, *18, and *21 (www.cypalleles.ki.se).7 The CYP2D6 genotypes of subjects were classified into 3 categories, namely, extensive metabolizers (EMs; genotypes including at least 1 active allele), intermediate metabolizers (IMs; 2 decreased‐activity alleles or 1 decreased‐activity allele and 1 inactive allele or 1 decreased‐activity allele and 1 unknown‐activity allele), and poor metabolizers (PMs; 2 inactive alleles).