ABSTRACT
Objective To investigate the effect of CYP2D6 gene polymorphism on risperidone (RISP) metabolism in schizophrenic patients. Methods CYP2D6 allele polymorphisms including*10,*4,*41 and *2 was detected by real-time fluorescent PCR in 120 schizophrenic patients who have taken risperidone continually. Alleles without SNP mutations were classified as wild-type (WT). At the same time, serum risperidone and 9-hydroxyrisperidone concentration of all patients were detected by mass spectrometric analysis. Some samples were selected for DNA sequencing of CYP2D6*10, which is the most common CYP2D6 allele in Oriental population. The 120 patients were divided into three groups according to their allele variants. Group 1 was defined as carriers of two functional alleles, group 2 was defined as carriers of one defective allele, group 3 was defined as carriers of two defective alleles. Genotype distributions, alleles frequencies, RISP, 9-oh-RISP, RISP+9-OH-RISP, 9-oh-RISP/RISP among three groups were calculated.Results Group 1 amount to 23 cases including 13 cases of WT/WT, 7 cases of*2/*2, 3 cases of WT/*2. Group 2 amount to 51 cases, including 38 cases of WT/*10, 8 cases of *2/*10, 1 case of *2/*41, 4 cases of WT/*41. Group 3 amount to 46 cases, including 44 cases of *10/*10, 2 cases of *10/*41. The*4 allele was not detected. The allele frequency of WT, *2, *10 and *41 was 29.6％, 10.8％, 56.7％ and 2.9％, respectively. The 9-hydroxyrisperidone/risperidone-ratio of three groups were 15.24±5.77, 11.06±4.56 and 2.39 ± 1.06, respectively. There was a significant difference in 9-hydroxyrisperidone/risperidone-ratio between Group 3 and the first two groups (P<0.001). Conclusions The frequency of *10 allele was the highest among the subjects. The frequency of WT and*2 allele was over 95％in the population. Individuals carrying one defective allele of CYP2D6 will decrease the rate of risperidone metabolism slightly, while individuals carrying two defective alleles of CYP2D6 may decrease the rate of risperidone metabolism significantly.