CYP2C19和CYP2C9基因型与苯妥英血药浓度关系的研究

目的　探讨细胞色素氧化酶P4 5 0 2C19(CYP2C19)和CYP2C9基因型对癫痫患者苯妥英血药浓度的影响。方法　对 32例癫痫患者应用变性高效液相技术分析中国人常见的 2个CYP2C19和 1个CYP2C9等位基因变异 ,应用荧光偏振免疫法测定患者苯妥英的血药浓度 ,在进行标准化以排除剂量和体重对血药浓度的影响后 ,分析CYP2C19和CYP2C9基因型和苯妥英血药浓度的关系。结果　服用单一苯妥英药物的 32例患者中 ,CYP2C19 2、CYP2C19 3和CYP2C9 3等位基因频率分别为 31%、8%和 6 %。根据携带CYP2C19和CYP2C9突变等位基因的数量 ,将患者分为基因型为CYP2C19 1/ 1合并CYP2C9 1/ 1的野生型纯合子强代谢者 (EM) ,基因型为CYP2C19 1/ 2或CYP2C19 1/ 3的杂合中间代谢者 (IM) ,基因型为CYP2C19 2 / 2或CYP2C19 2 / 3或CYP2C19 1/ 2合并CYP2C9 1/ 3的突变型纯合子弱代谢者 (PM)。 3组频率分别为 34%、4 4 %、和 2 2 %。并且突变基因携带数量与标准化血药浓度呈正相关。PM患者服用同等剂量苯妥英时血药浓度比EM患者高 34% (P <0 0 1)。结论　苯妥英代谢受CYP2C9和CYP2C19基因调控。根据患者CYP2C19和CYP2C9基因型可以预测患者的药物浓度 ,有利于临床选择适宜的苯妥英初始剂量

Association between genetic polymorphisms of CYP2C19 and CYP2C9 and phenytoin serum concentration

OBJECTIVE: To investigate the relationship between the genetic polymorphism of cytochrome CYP2C19 and CYP2C9 and the serum concentration of phenytoin (PHT) in patients with epilepsy. METHODS: The peripheral blood samples of 200 patients with epilepsy aged 2 - 68, were collected to undergo PCR. Denaturing high performance liquid chromatography (DHPLC) was used to detect the PCR products so as to examined the 2 common CYP2C19 allele variants and one CYP2C9 allele. The patients were treated with PHT of the dosage of 1.00 - 18.02 mg/kg alone. After 5 half-life periods venous blood was collected before the administration. Fluorescence polarization immunoassay was used to measure the PHT serum concentration standardized by dosage and body weight. RESULTS: The allele frequencies of CYP2C19 * 2, CYP2C19 * 3, and CYP2C9 * 3 were 31%, 8%, and 6% respectively. Thirty-two patients with CYP2C19 and/or CYP2C9 allele variants were classified into 3 groups: extensive metabolizer (EM, n = 11) homozygous for CYP2C19 * 1/* 1 combined with CYP2C9 * 1/* 1 alleles, intermediate metabolizer (IM, n = 14) heterozygous for CYP2C19 * 1/* 2 or CYP2C19 * 1/* 3 alleles, and poor metabolizer (PM, n = 7) with the genotype of CYP2C19 * 2/* 2 or CP2C19 * 2/* 3, or CYP2C19 * 1/* 2 combined with CYP2C9 * 1/* 3. The genotype distribution rates of EM, IM, and PM were 34%, 44%, and 22% respectively. The PHT serum concentration of the PM group was (4.0 +/- 0.9) Css, significantly higher than that of the IM group [(3.0 +/- 0.9) Css, P < 0.05] and that of the EM group [(2.6 +/- 0.8) Css, P < 0.01] without a significant difference between the IM group and EM group. CONCLUSION: Phenytoin is metabolized via CYP2C19 and CYP2C9. The PHT serum concentration of the PM is significantly higher. Genotyping helps predict the clinical response to PHT administration.