Olesen O V, Linnet K
Institute for Basic Psychiatric Research, Department of Biological Psychiatry, Psychiatric University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark.
Br J Clin Pharmacol. 2000 Dec;50(6):563-71. doi: 10.1046/j.1365-2125.2000.00298.x.
To identify the human cytochrome P450 (CYP) isoforms mediating the N-dealkylation of the antipsychotic drug perphenazine in vitro and estimate the relative contributions of the CYP isoforms involved.
cDNA-expressed CYP isoforms were used to identify the isoforms that are able to mediate the N-dealkylation of perphenazine, which is considered a major metabolic pathway for the drug. Using human liver microsomal preparations (HLM), inhibition studies were carried out to establish the relative contributions of the CYP isoforms involved in the N-dealkylation reaction.
CYP isoforms 1A2, 3A4, 2C8, 2C9, 2C18, 2C19 and 2D6 were able to mediate the N-dealkylation of perphenazine. Reaction velocities and their relative abundance in HLM suggested that CYP1A2, 3A4, 2C19 and 2D6 were the most important contributors to N-dealkylation. Apparent Km values of CYP1A2 and CYP2D6 were in the range 1-2 microM, and Km values of CYP2C19 and CYP3A4 were 14 microM and 7.9 microM, respectively. Ketoconazole inhibition of N-dealkylation mediated by a mixed HLM indicated that CYP3A4 accounted for about 40% of perphenazine N-dealkylation at therapeutically relevant concentrations. The contribution of the CYP isoforms 1A2, 2C19 and 2D6 amounted to 20-25% each as measured by the percentage inhibition obtained by addition of furafylline, fluvoxamine or quinidine, respectively. HLM-mediated N-dealkylation of perphenazine accounted for 57% of the total amount of substrate consumed during incubation.
The present in vitro study suggests that CYP isoforms 1A2, 3A4, 2C19 and 2CD6 are primarily involved in the N-dealkylation of perphenazine. The relatively modest role of CYP2D6 is at variance with in vivo studies, which indicate a greater contribution of this isoform. Alternative metabolic pathways, corresponding to 43% of the HLM-mediated metabolism of the drug, may depend more strongly on CYP2D6.
鉴定在体外介导抗精神病药物奋乃静N-去烷基化反应的人细胞色素P450（CYP）同工酶，并评估所涉及的CYP同工酶的相对贡献。
利用cDNA表达的CYP同工酶来鉴定能够介导奋乃静N-去烷基化反应的同工酶，该反应被认为是该药物的主要代谢途径。使用人肝微粒体制剂（HLM）进行抑制研究，以确定参与N-去烷基化反应的CYP同工酶的相对贡献。
CYP同工酶1A2、3A4、2C8、2C9、2C18、2C19和2D6能够介导奋乃静的N-去烷基化反应。反应速度及其在HLM中的相对丰度表明，CYP1A2、3A4、2C19和2D6是N-去烷基化反应的最重要贡献者。CYP1A2和CYP2D6的表观Km值在1 - 2 microM范围内，CYP2C19和CYP3A4的Km值分别为14 microM和7.9 microM。酮康唑对混合HLM介导的N-去烷基化反应的抑制作用表明，在治疗相关浓度下，CYP3A4约占奋乃静N-去烷基化反应的40%。通过分别添加呋拉茶碱、氟伏沙明或奎尼丁获得的抑制百分比测量，CYP同工酶1A2、2C19和2D6的贡献分别为20 - 25%。HLM介导的奋乃静N-去烷基化反应占孵育过程中消耗的底物总量的57%。
目前的体外研究表明，CYP同工酶1A2、3A4、2C19和2CD6主要参与奋乃静的N-去烷基化反应。CYP2D6相对较小的作用与体内研究结果不同，体内研究表明该同工酶的贡献更大。对应于该药物HLM介导代谢的43%的替代代谢途径可能更强烈地依赖于CYP2D6。
