The involvement of CYP enzymes in the metabolism of citalopram was studied, inclusive the conversion of demethylcitalopram to didemethylcitalopram and the formation of citalopram N-oxide, which both have not been considered previously. Using human mixed liver microsomes and cDNA-expressed CYP enzymes, we confirmed that CYP3A4, 2C19 and 2D6 are involved in the first demethylation step of citalopram, all favouring conversion of the biologically active S-enantiomer. Inhibitor studies indicated that at therapeutic citalopram concentrations CYP3A4 was responsible for 40–50% of demethylcitalopram formation, while the contribution of CYP2C19 increased and that of CYP2D6 tended to decrease with increasing drug concentration. CYP2D6 exclusively mediated the second demethylation step, and citalopram N-oxide was also exclusively formed by CYP2D6. None of the studied CYP enzymes mediated deamination to the propionic acid derivative.
研究了CYP酶在西酞普兰代谢中的参与情况,包括去甲基西酞普兰转化为二甲基西酞普兰以及西酞普兰N-氧化物的形成,这两个过程以前都没有被考虑过。使用人类混合肝微粒体和cDNA表达的CYP酶,我们确认CYP3A4、2C19和2D6参与了西酞普兰的第一次去甲基化步骤,都有利于将生物活性的S-对映体转化为。抑制剂研究表明,在治疗性西酞普兰浓度下,CYP3A4负责40-50%的去甲基西酞普兰形成,而CYP2C19的贡献随药物浓度增加而增加,CYP2D6的贡献则倾向于随药物浓度增加而减少。CYP2D6独家介导第二次去甲基化步骤,西酞普兰N-氧化物也完全由CYP2D6形成。研究的CYP酶中没有介导去氨基反应生成丙酸衍生物。