Dalmadi Balázs, Leibinger János, Szeberényi Szabolcs, Borbás Tímea, Farkas Sándor, Szombathelyi Zsolt, Tihanyi Károly
Division of Pharmacology and Drug Safety Research, Gedeon Richter Ltd., Budapest, Hungary.
Drug Metab Dispos. 2003 May;31(5):631-6. doi: 10.1124/dmd.31.5.631.
The in vitro metabolism of tolperisone, 1-(4-methyl-phenyl)-2-methyl-3-(1-piperidino)-1-propanone-hydrochloride, a centrally acting muscle relaxant, was examined in human liver microsomes (HLM) and recombinant enzymes. Liquid chromatography-mass spectrometry measurements revealed methyl-hydroxylation (metabolite at m/z 261; M1) as the main metabolic route in HLM, however, metabolites of two mass units greater than the parent compound and the hydroxy-metabolite were also detected (m/z 247 and m/z 263, respectively). The latter was identified as carbonyl-reduced M1, the former was assumed to be the carbonyl-reduced parent compound. Isoform-specific cytochrome P450 (P450) inhibitors, inhibitory antibodies, and experiments with recombinant P450s pointed to CYP2D6 as the prominent enzyme in tolperisone metabolism. CYP2C19, CYP2B6, and CYP1A2 are also involved to a smaller extent. Hydroxymethyl-tolperisone formation was mediated by CYP2D6, CYP2C19, CYP1A2, but not by CYP2B6. Tolperisone competitively inhibited dextromethorphan O-demethylation and bufuralol hydroxylation (K(i) = 17 and 30 microM, respectively). Tolperisone inhibited methyl p-tolyl sulfide oxidation (K(i) = 1200 microM) in recombinant flavin-containing monooxygenase 3 (FMO3) and resulted in a 3-fold (p < 0.01) higher turnover number using rFMO3 than that of control microsomes. Experiments using nonspecific P450 inhibitors-SKF-525A, 1-aminobenzotriazole, 1-benzylimidazole, and anti-NADPH-P450-reductase antibodies-resulted in 61, 47, 49, and 43% inhibition of intrinsic clearance in HLM, respectively, whereas hydroxymethyl-metabolite formation was inhibited completely by nonspecific chemical inhibitors and by 80% with antibodies. Therefore, it was concluded that tolperisone undergoes P450-dependent and P450-independent microsomal biotransformations to the same extent. On the basis of metabolites formed and indirect evidences of inhibition studies, a considerable involvement of a microsomal reductase is assumed.
中枢性肌肉松弛剂托哌酮（1-(4-甲基苯基)-2-甲基-3-(1-哌啶基)-1-丙酮盐酸盐）在人肝微粒体（HLM）和重组酶中的体外代谢情况得到了研究。液相色谱 - 质谱测量显示，甲基羟基化（质荷比为261的代谢物；M1）是HLM中的主要代谢途径，然而，还检测到了比母体化合物质量大两个质量单位的代谢物以及羟基代谢物（分别为质荷比247和263）。后者被鉴定为羰基还原的M1，前者被认为是羰基还原的母体化合物。同工酶特异性细胞色素P450（P450）抑制剂、抑制性抗体以及重组P450实验表明，CYP2D6是托哌酮代谢中的主要酶。CYP2C19、CYP2B6和CYP1A2也有较小程度的参与。羟甲基托哌酮的形成由CYP2D6、CYP2C19、CYP1A2介导，但不由CYP2B6介导。托哌酮竞争性抑制右美沙芬O - 去甲基化和布非洛尔羟基化（抑制常数分别为17和30微摩尔）。托哌酮抑制重组含黄素单加氧酶3（FMO3）中对甲苯基硫醚的甲基氧化（抑制常数为1200微摩尔），并且使用重组FMO3时的周转数比对照微粒体高3倍（p < 0.01）。使用非特异性P450抑制剂 - SKF - 525A、1 - 氨基苯并三唑、1 - 苄基咪唑以及抗NADPH - P450还原酶抗体的实验分别导致HLM中内在清除率抑制61%、47%、49%和43%，而羟甲基代谢物的形成被非特异性化学抑制剂完全抑制，被抗体抑制80%。因此，可以得出结论，托哌酮在相同程度上经历了P450依赖性和P450非依赖性微粒体生物转化。基于形成的代谢物以及抑制研究的间接证据，推测微粒体还原酶有相当大的参与。
