10种心血管类中药注射剂对人细胞色素P_(450)7种亚型的体外抑制作用

目的:研究10种心血管类中药注射剂对人细胞色素P450(CYP)7种亚型(CYP1A2、CYP2B6、CYP2C8、CYP2C9、CYP2C19、CYP2D6、CYP3A4/5)的体外抑制作用。方法:10种心血管类中药注射剂9个不同质量浓度的工作液分别与7种CYP亚型对应的混合探针药物在人肝微粒体中共同孵育,采用高效液相色谱-串联质谱(LC-MS/MS)法同时测定这7种探针药物的代谢产物,即对乙酰氨基酚(CYP1A2)、羟基安非他酮(CYP2B6)、去甲阿莫地喹(CYP2C8)、4-羟基双氯芬酸(CYP2C9)、4-羟基美芬妥英(CYP2C19)、右啡烷(CYP2D6)、1-羟基咪达唑仑(CYP3A4/5)的质量浓度,计算半数抑制浓度(IC50),并确定对CYP有抑制作用的中药注射剂。结果:CYP1A2、CYP2B6、CYP2C8、CYP2C9、CYP2C19、CYP2D6、CYP3A4/5的阳性抑制剂呋拉茶碱、塞替派、槲皮素、磺胺苯吡唑、噻氯匹定、奎尼丁和酮康唑对相应酶型均表现出明显抑制作用;10种心血管类中药注射剂中丹红注射液对CYP1A2、CYP2B6、CYP2C8、CYP2C9、CYP2C19、CYP2D6和CYP3A4/5均有明显抑制作用,红花注射液对CYP2C8有明显抑制作用。结论:在正常体积分数/质量浓度下,丹红注射液对人CYP 7种亚型在体外均有明显抑制作用;红花注射液对人CYP2C8在体外有明显抑制作用。     

消癌平注射液等4种抗肿瘤中药注射剂对人肝微粒体中CYP450酶7种亚型的体外抑制作用研究

目的：考察消癌平注射液等4种抗肿瘤中药注射剂对人肝微粒体CYP450酶7种亚型CYP1A2、CYP2B6、CYP2C8、CYP2C9、CYP2C19、CYP2D6和CYP3A4／5的体外抑制作用。方法：消癌平注射液等4种抗肿瘤中药注射剂分别与7种CYP450酶亚型对应的混合探针药物在人肝微粒体中共同孵育,采用液相色谱-串联质谱（LC—MS／MS）法同时测定这7种探针药物的代谢产物：对乙酰氨基酚、羟基安非他酮、去甲阿莫地喹、4-羟基双氯芬酸、4-羟基美芬妥英、右啡烷和1-羟基咪达唑仑的浓度,分别代表CYP1A2、CYP2B6、CYP2C8、CYP2C9、CYP2C19、CYP2D6和CYP3A4／5的活性,其对CYP450酶亚型的抑制程度以IC50值表示。结果：在体外人肝微粒体孵育体系中,消癌平注射液对CYP1A2、CYP2B6、CYP2C8、CYP2C9、CYP2C19和CYP3A4／5的IC50值分别为0．51％、1．34％、1．42％、0．939／6、1．09％和0．75％,艾迪注射液对CYP2C8的IC50值为0．21％;消癌平注射液对CYP2D6的IC10值为2．58％,艾迪注射液对CYP2B6、CYP2C9、CYP2C19和CYP3A4／5的IC50值分别为13．24％、16．31％、4．27％和3．73％,华蟾素注射液对CYP1A2、CYP2B6、CYP2C8和CYP2D6的IC50值分别为3．50％、28．01％、20．32％和32．59％,康艾注射液对CYP1A2、CYP2B6、CYP2C8、CYP2D6和CYP3A4／5的IC50值分别为2．55％、15．32％、1．44％、1．72％和3．99％,均高于各自的日用药量浓度;在测定浓度范围内,艾迪注射液对CYP1A2和CYP2D6,华蟾素注射液对CYP2C9、CYP2C19和CYP3A4／5,康艾注射液对CYP2C9和CYP2C19的活性抑制率均小于50％。结论：在体外,正常剂量下,消癌平注射液对人CYP1A2、CYP2B6、CYP2C8、CYP2C9、CYP2C19和CYP3A4／5,艾迪注射液体对人CYP2C8均有明显抑制作用;消癌平注射液对CYP2D6,艾迪注射液对CYP2B6、CYP2C9、CYP2C19和CYP3A4／5,华蟾素注射液对CYP1A2、CYP2B6、CYP2C8和CYP2D6,康艾注射液对CYP1A2、CYP2B6、CYP2C8、CYP2D6和CYP3A4／5,均无明显抑制作用;艾迪注射液对CYP1A2和CYP2D6,华蟾素注射液对CYP2C9、CYP2C19和CYP3A4／5,康艾注射液对CYP2C9和CYP2C19,均无抑制作用。     

瓜蒌皮注射液对人肝微粒体CYP450酶4种亚型的影响

目的研究瓜蒌皮注射液对人肝细胞色素P450(CYP450)酶4种亚型CYP1A2、CYP2B6、CYP2C9和CYP2D6的体外抑制作用。方法瓜蒌皮注射液8个不同浓度(2%、1%、0.2%、0.05%、0.01%、0.005%、0.002%、0.000 5%)的工作液分别与4种CYP450酶亚型的探针底物混合,即非那西丁(CYP1A2)、安非他酮(CYP2B6)、双氯芬酸(CYP2C9)、右美沙芬(CYP2D6),用维拉帕米作为内标,在人肝微粒体中孵育,采用高效液相色谱法检测4种探针底物的剩余浓度,计算半数抑制浓度(IC_(50))。结果瓜蒌皮注射液对CYP1A2、CYP2B6、CYP2C9和CYP2D6的IC_(50)值均大于临床常用量。结论正常用量下,瓜蒌皮注射液对人CYP450酶的4亚型无明显影响。     

评价HPPH对细胞色素P450酶体外代谢活性的影响

目的:评价HPPH在体外对大鼠及人肝微粒CYP450酶的6种亚型酶活性的影响,预测使用HPPH可能出现的药物相互作用。方法:将注射用HPPH与CYP450酶的6种亚型的特异性探针底物非那西汀(CYP1A2)、甲苯磺丁脲(CYP2C9)、S-美芬妥因(CYP2C19)、右美沙芬(CYP2D6)、氯唑沙宗(CYP2E1)、咪达唑仑(CYP3A4)和睾酮(CYP3A4)与大鼠及人肝微粒进行孵育反应,采用HPLC-MS/MS法测定对应的7种代谢产物(对乙酰氨基酚、羟基甲苯磺丁脲、4-羟基美芬妥因、O-去甲基右美沙芬、6-羟基氯唑沙宗、1′-羟基咪达唑仑、6β-羟基睾酮)的浓度。结果:在本实验条件下,HPPH浓度为1.00~50.00μmol·L-1时,未发现其对大鼠的CYP1A2、CYP2C9、CYP2D6、CYP2E1、CYP3A4产生抑制作用。在本实验条件下,HPPH浓度为0.50~10.00μmol·L-1时,未发现其对人CYP1A2产生抑制作用;但对人CYP2C9、CYP2C19、CYP2D6、CYP2E1均存在抑制作用;对人CYP3A4,对底物咪达唑仑存在抑制作用,对底物睾酮未发现抑制作用。结论:HPPH对CYP450酶的抑制作用存在种属差异,在人体内HPPH与CYP450酶作用有待体内实验进一步证明。     

甲基原薯蓣皂苷对人肝微粒体中7种CYP450酶活性的影响

目的研究甲基原薯蓣皂苷对CYP450酶的7种亚型酶活性的影响。方法将MPD和CYP450酶7种亚型的特异性探针底物咖啡因(CYP1A2)、右美沙芬(CYP2D6)、甲苯磺丁脲(CYP2C9)、s-美芬妥因(CYP2C19)、氯唑沙宗(CYP2E1)、香豆素(CYP2A6)及咪达唑仑(CYP3A4)与人肝微粒体进行孵化反应,采用HPLC和LC-MS/MS法测定对应的7种代谢产物(1,7-二甲基黄嘌呤、去甲右美沙芬、4-羟基甲苯磺丁脲、4-羟基美芬妥因、6-羟基氯唑沙宗、7-羟基香豆素和1-羟基咪达唑仑)的浓度,通过与对照组比较,确定MPD对以上7种酶活性的影响。结果MPD在1~10μmol.L-1时对7种酶均无明显抑制作用,在100μmol.L-1时对CYP2D6有抑制趋势,但对其他6种酶无抑制作用,均无统计学意义(P>0.05)。结论MPD在与以上6种酶(CYP1A2、CYP2E1、CYP2C19、CYP3A4、CYP2C9和CYP2A6)代谢的药物联合用药时,发生药物相互作用的可能性较小。     

罗通定和羟考酮体外代谢的相互作用

目的体外实验考察罗通定(RTD)和羟考酮(OCD)对细胞色素P450(CYP)同工酶的抑制和诱导作用,分析预测两药合用时潜在的药物代谢性相互作用。方法将混合人肝微粒体与RTD,OCD或阳性抑制剂与CYP探针底物孵育30min,用高效液相色谱-质谱法测定孵育液中特异性探针底物代谢产物的生成率、得到各同工酶的相对活性并计算相应的CYP同工酶的IC50值,评价两药对CYP1A2,CYP2C9,CYP2C19,CYP2D6和CYP3A4的潜在抑制作用。RTD(20,200和2000μg·L-1)、OCD(2,20和200μg.L-1)或阳性诱导剂与原代SD大鼠肝细胞孵育72h后加入特异性探针底物再孵育60min、测定细胞孵育液中探针底物的清除率、计算得到相对酶活性,通过与阳性诱导剂组的比较评价RTD和OCD对CYP1A和CYP3A的诱导作用。结果OCD对CYP1A2,CYP2C9,CYP2C19,CYP2D6和CYP3A4均无诱导和抑制作用。RTD对CYP2D6有一定的抑制作用,IC50值为3.72μmol·L-1,除此之外对其他的CYP同工酶无诱导和抑制作用。结论RTD是CYP2D6的一个中等程度的抑制剂,在体内血浆水平相当或高于其IC50值(3.72μmol·L-1)时,RTD对OCD经CYP2D6酶介导的O-去甲基化代谢途径有一定的抑制作用,但是在临床常用剂量水平上RTD和OCD临床合用产生明显的代谢性相互作用的可能性很小。     

LC-MS/MS法研究黄酮类化合物对人肝微粒体细胞色素P450酶6种亚型的体外抑制作用

目的：建立液相色谱-串联质谱法（LC-MS/MS）研究黄酮类化合物对人肝微粒体细胞色素P450酶6种亚型的 体外抑制作用。方法：采用ESI正离子和负离子选择反应检测同时测定扑热息痛、4-羟基甲苯磺丁脲、5-羟基奥美拉唑 、氧去甲基右美沙芬、6-羟基氯唑沙宗和氧化硝苯地平,分别代表CYP1A2,CYP2C9,CYP2C19,CYP2D6,CYP2E1, CYP3A4的活性;黄酮类化合物和6种探针底物在人肝微粒体中共同孵育,并计算其IC50值表示对CYP450酶的抑制程度。 结果：黄酮苷类（水飞蓟宾、金丝桃苷、儿茶素、表儿茶素、葛根素、芦丁、甘草苷以及柚皮苷）的IC50 值均大于50 μmol?L-1,对6种亚型没有抑制作用。而黄酮苷元如槲皮素等均能不同程度地抑制CYP1A2,IC50值从0.054 μmol?L-1 到31.91 μmol?L-1不等;有些对其他亚型如 CYP2C9,CYP2C19,CYP2E1,CYP3A4 也有一定的抑制作用。所有的黄酮类 化合物对CYP2D6无抑制活性。黄酮对CYP3A4的活性也有激活作用。结论：建立的LC-MS/MS方法准确、灵敏、可靠。33种 黄酮类化合物对CYP450酶6种亚型有不同的抑制作用,这些信息有助于中药-药物相互作用的预测。     

LC-MS/MS法研究黄酮类化合物对人肝微粒体细胞色素P450酶6种亚型的体外抑制作用

目的：建立液相色谱-串联质谱法（LC-MS/MS）研究黄酮类化合物对人肝微粒体细胞色素P450酶6种亚型的 体外抑制作用。方法：采用ESI正离子和负离子选择反应检测同时测定扑热息痛、4-羟基甲苯磺丁脲、5-羟基奥美拉唑 、氧去甲基右美沙芬、6-羟基氯唑沙宗和氧化硝苯地平，分别代表CYP1A2，CYP2C9，CYP2C19，CYP2D6，CYP2E1， CYP3A4的活性；黄酮类化合物和6种探针底物在人肝微粒体中共同孵育，并计算其IC50值表示对CYP450酶的抑制程度。 结果：黄酮苷类（水飞蓟宾、金丝桃苷、儿茶素、表儿茶素、葛根素、芦丁、甘草苷以及柚皮苷）的IC50 值均大于50 μmol?L-1，对6种亚型没有抑制作用。而黄酮苷元如槲皮素等均能不同程度地抑制CYP1A2，IC50值从0.054 μmol?L-1 到31.91 μmol?L-1不等；有些对其他亚型如 CYP2C9，CYP2C19，CYP2E1，CYP3A4 也有一定的抑制作用。所有的黄酮类 化合物对CYP2D6无抑制活性。黄酮对CYP3A4的活性也有激活作用。结论：建立的LC-MS/MS方法准确、灵敏、可靠。33种 黄酮类化合物对CYP450酶6种亚型有不同的抑制作用，这些信息有助于中药-药物相互作用的预测。     

LC-MS/MS法研究黄酮类化合物对人肝微粒体细胞色素P450酶6种亚型的体外抑制作用

目的：建立液相色谱-串联质谱法（LC-MS/MS）研究黄酮类化合物对人肝微粒体细胞色素P450酶6种亚型的 体外抑制作用。方法：采用ESI正离子和负离子选择反应检测同时测定扑热息痛、4-羟基甲苯磺丁脲、5-羟基奥美拉唑 、氧去甲基右美沙芬、6-羟基氯唑沙宗和氧化硝苯地平，分别代表CYP1A2，CYP2C9，CYP2C19，CYP2D6，CYP2E1， CYP3A4的活性；黄酮类化合物和6种探针底物在人肝微粒体中共同孵育，并计算其IC50值表示对CYP450酶的抑制程度。 结果：黄酮苷类（水飞蓟宾、金丝桃苷、儿茶素、表儿茶素、葛根素、芦丁、甘草苷以及柚皮苷）的IC50 值均大于50 μmol?L-1，对6种亚型没有抑制作用。而黄酮苷元如槲皮素等均能不同程度地抑制CYP1A2，IC50值从0.054 μmol?L-1 到31.91 μmol?L-1不等；有些对其他亚型如 CYP2C9，CYP2C19，CYP2E1，CYP3A4 也有一定的抑制作用。所有的黄酮类 化合物对CYP2D6无抑制活性。黄酮对CYP3A4的活性也有激活作用。结论：建立的LC-MS/MS方法准确、灵敏、可靠。33种 黄酮类化合物对CYP450酶6种亚型有不同的抑制作用，这些信息有助于中药-药物相互作用的预测。     

LC-MS/MS法研究黄酮类化合物对人肝微粒体细胞色素P450酶6种亚型的体外抑制作用

目的：建立液相色谱-串联质谱法（LC-MS/MS）研究黄酮类化合物对人肝微粒体细胞色素P450酶6种亚型的 体外抑制作用。方法：采用ESI正离子和负离子选择反应检测同时测定扑热息痛、4-羟基甲苯磺丁脲、5-羟基奥美拉唑 、氧去甲基右美沙芬、6-羟基氯唑沙宗和氧化硝苯地平，分别代表CYP1A2，CYP2C9，CYP2C19，CYP2D6，CYP2E1， CYP3A4的活性；黄酮类化合物和6种探针底物在人肝微粒体中共同孵育，并计算其IC50值表示对CYP450酶的抑制程度。 结果：黄酮苷类（水飞蓟宾、金丝桃苷、儿茶素、表儿茶素、葛根素、芦丁、甘草苷以及柚皮苷）的IC50 值均大于50 μmol?L-1，对6种亚型没有抑制作用。而黄酮苷元如槲皮素等均能不同程度地抑制CYP1A2，IC50值从0.054 μmol?L-1 到31.91 μmol?L-1不等；有些对其他亚型如 CYP2C9，CYP2C19，CYP2E1，CYP3A4 也有一定的抑制作用。所有的黄酮类 化合物对CYP2D6无抑制活性。黄酮对CYP3A4的活性也有激活作用。结论：建立的LC-MS/MS方法准确、灵敏、可靠。33种 黄酮类化合物对CYP450酶6种亚型有不同的抑制作用，这些信息有助于中药-药物相互作用的预测。     

黄连解毒汤对人细胞色素P450酶6个亚型的体外抑制作用研究

目的:研究黄连解毒汤对人肝微粒体6个亚型CYP1A2、CYP2C8、CYP2C9、CYP2C19、CYP2D6和CYP3A4的体外抑制作用。方法:采用液相色谱-串联质谱法(LC-MS/MS)同时测定对乙酰氨基酚、6α-羟基紫杉醇、4-羟基双氯芬酸、4-羟基美芬妥英、右啡烷、1-羟基咪达唑仑和6β-羟基睾酮,分别代表CYP1A2、CYP2C8、CYP2C9、CYP2C19、CYP2D6和CYP3A4的活性;黄连解毒汤提取物和7种混合探针底物在人肝微粒体中共同孵育,并计算其IC50值表示对CYP450酶的抑制程度。结果:在人肝微粒体体外孵育体系中,黄连解毒汤对CYP2D6的IC50值为3.54μg/mL,对CYP1A2的IC50值为10.8μg/mL,对CYP2C8、CYP2C9、CYP2C19、CYP3A4_T和CYP3A4_M亚酶的IC50值依次为67.7、299、530、199和607μg/mL。结论:在正常剂量下,黄连解毒汤对人肝微粒体CYP2D6和1A2可能有抑制作用,对人肝微粒体CYP2C8、CYP2C9、CYP2C19和CYP3A4无明显抑制作用。     

Investigation of drug-drug interaction potential of bortezomib in vivo in female Sprague-Dawley rats and in vitro in human liver microsomes.

Bortezomib (Velcade, PS-341), a dipeptidyl boronic acid, is a first-in-class proteasome inhibitor approved in 2003 for the treatment of multiple myeloma. In a preclinical toxicology study, bortezomib-treated rats resulted in liver enlargement (35%). Ex vivo analyses of the liver samples showed an 18% decrease in cytochrome P450 (P450) content, a 60% increase in palmitoyl coenzyme A beta-oxidation activity, and a 41 and 23% decrease in CYP3A protein expression and activity, respectively. Furthermore, liver samples of bortezomib-treated rats had little change in CYP2B and CYP4A protein levels and activities. To address the likelihood of clinical drug-drug interactions, the P450 inhibition potential of bortezomib and its major deboronated metabolites M1 and M2 and their dealkylated metabolites M3 and M4 was evaluated in human liver microsomes for the major P450 isoforms 1A2, 2C9, 2C19, 2D6, and 3A4/5. Bortezomib, M1, and M2 were found to be mild inhibitors of CYP2C19 (IC(50) approximately 18.0, 10.0, and 13.2 microM, respectively), and M1 was also a mild inhibitor of CYP2C9 (IC(50) approximately 11.5 microM). However, bortezomib, M1, M2, M3, and M4 did not inhibit other P450s (IC(50) values > 30 microM). There also was no time-dependent inhibition of CYP3A4/5 by bortezomib or its major metabolites. Based on these results, no major P450-mediated clinical drug-drug interactions are anticipated for bortezomib or its major metabolites. To our knowledge, this is the first report on P450-mediated drug-drug interaction potential of proteasome inhibitors or boronic acid containing therapeutics.     

Inhibition of human recombinant cytochrome P450s by curcumin and curcumin decomposition products

Curcumin (diferuloylmethane) is a major yellow pigment and dietary component derived from Curcuma longa. It has potent anti-inflammatory, anticarcinogenic, antioxidant and chemoprotective activities among others. We studied the interactions of curcumin, a mixture of its decomposition products, and four of its individually identified decomposition products (vanillin, vanillic acid, ferulic aldehyde and ferulic acid) on five major human drug-metabolizing cytochrome P450s (CYPs). Curcumin inhibited CYP1A2 (IC(50), 40.0 microM), CYP3A4 (IC(50), 16.3 microM), CYP2D6 (IC(50), 50.3 microM), CYP2C9 (IC(50), 4.3 microM) and CYP2B6 (IC(50), 24.5 microM). Curcumin showed a competitive type of inhibition towards CYP1A2, CYP3A4 and CYP2B6, whereas a non-competitive type of inhibition was observed with respect to CYP2D6 and CYP2C9. The inhibitory activity towards CYP3A4, shown by curcumin may have implications for drug-drug interactions in the intestines, in case of high exposure of the intestines to curcumin upon oral administration. In spite of the significant inhibitory activities shown towards the major CYPs in vitro, it remains to be established, whether curcumin will cause significant drug-drug interactions in the liver, given the reported low systemic exposure of the liver to curcumin. The decomposition products of curcumin showed no significant inhibitory activities towards the CYPs investigated, and therefore, are not likely to cause drug-drug interactions at the level of CYPs.     

体外“鸡尾酒法”研究5-羟基雷公藤内酯醇对人肝微粒体CYP450酶亚型的抑制

目的：评价（5R）-5-羟基雷公藤内酯醇（T8）在体外对人肝微粒体CYP450酶7种主要亚型CYP3A／5、CYP2D6、CYPlA2、CYP2C9、CYP2C19、CYP286和CYP2C8的直接抑制作用和时间依赖性抑制作用,为临床药物一药物相互作用研究提供指导。方法：本实验分别利用IC50和IC50偏移进行评价。结果：T8对上述7种亚型的直接抑制IC50都高于100μmol／L,时间依赖性抑制研究中没有出现IC50偏移。结论：T8对7种主要的CYP450酶亚型没有直接抑制和时间依赖性抑制作用。临床上发生由于T8抑制上述7种亚型的CYP450酶导致的药物一药物相互作用的可能性较小。     

Metabolism and related human risk factors for hepatic damage by usnic acid containing nutritional supplements

Usnic acid is a component of nutritional supplements promoted for weight loss that have been associated with liver-related adverse events including mild hepatic toxicity, chemical hepatitis, and liver failure requiring transplant. To determine if metabolism factors might have had a role in defining individual susceptibility to hepatotoxicity, in vitro metabolism studies were undertaken using human plasma, hepatocytes, and liver subcellular fractions. Usnic acid was metabolized to form three monohydroxylated metabolites and two regio-isomeric glucuronide conjugates of the parent drug. Oxidative metabolism was mainly by cytochrome P450 (CYP) 1A2 and glucuronidation was carried out by uridine diphosphate-glucuronosyltransferase (UGT) 1A1 and UGT1A3. In human hepatocytes, usnic acid at 20 microM was not an inducer of CYP1A2, CYP2B6, or CYP3A4 relative to positive controls omeprazole, phenobarbital, and rifampicin, respectively. Usnic acid was a relatively weak inhibitor of CYP2D6 and a potent inhibitor of CYP2C19 (the concentration eliciting 50% inhibition (IC(50)) = 9 nM) and CYP2C9 (IC(50) = 94 nM), with less potent inhibition of CYP2C8 (IC(50) = 1.9 microM) and CYP2C18 (IC(50) = 6.3 microM). Pre-incubation of microsomes with usnic acid did not afford any evidence of time-dependent inhibition of CYP2C19, although evidence of slight time-dependent inhibition of CYP2C9 (K(I) = 2.79 microM and K(inact) = 0.022 min(-1)) was obtained. In vitro data were used with SimCYP(R)to model potential drug interactions. Based on usnic acid doses in case reports of 450 mg to >1 g day(-1), these in vitro data indicate that usnic acid has significant potential to interact with other medications. Individual characteristics such as CYP1A induction status, co-administration of CYP1A2 inhibitors, UGT1A1 polymorphisms, and related hyperbilirubinaemias, or co-administration of low therapeutic index CYP2C substrates could work alone or in consort with other idiosyncrasy risk factors to increase the risk of adverse events and/or hepatotoxicity. Thus, usnic acid in nutritional supplements might be involved as both victim and/or perpetrator in clinically significant drug-drug interactions.     

Inhibitory effect of glyburide on human cytochrome p450 isoforms in human liver microsomes.

The inhibitory effect of glyburide [International Nonproprietary Name (INN), glibenclamide] on CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 activities was evaluated using pooled human liver microsomes. Glyburide strongly inhibited CYP2C9-catalyzed S-warfarin and phenytoin metabolism in a competitive manner, with Ki (IC50) values of 2.4 (11.3) microM and 3.1 (9.4) microM, respectively. CYP3A4-catalyzed midazolam 1-hydroxylation was inhibited by glyburide with a Ki (IC50) value of 42.5 (90.0) microM. However, glyburide showed no appreciable inhibitory effect on CYP1A2, CYP2C8, CYP2C19, CYP2E1, or CYP2D6. In summary, glyburide showed potent inhibition on CYP2C9 and weak inhibition on CYP3A4, whereas it had minimal or no inhibitory effect on the other cytochromes p450 examined. It is anticipated that clinically significant drug-drug interactions will ensue when glyburide is coadministered with agents that are cleared primarily by the CYP2C9-mediated pathway and those with narrow therapeutic ranges.     

Evaluation of p450 inhibition and induction by artemisinin antimalarials in human liver microsomes and primary human hepatocytes

Artemisinin drugs have become the first-line antimalarials in areas of multidrug resistance. However, monotherapy with artemisinin drugs results in comparatively high recrudescence rates. Autoinduction of cytochrome P450 (P450)-mediated metabolism, resulting in reduced exposure, has been supposed to be the underlying mechanism. To better understand the autoinduction and metabolic drug-drug interactions (DDIs), we evaluated the P450s (particularly CYP2B6 and CYP3A4) inhibited or induced by two artemisinin drugs, Qing-hao-su (QHS) and dihydroartemisinin (DHA) using human liver microsome, recombinant P450 enzymes, and primary human hepatocytes. The results suggested that QHS was a weak reversible inhibitor of CYP2B6 (K(i) 4.6 μM), but not CYP3A4 (IC(50) ～ 50 μM) and did not show measurable time-dependent inhibition of either CYP2B6 or CYP3A4. DHA inhibited neither CYP2B6 nor CYP3A4 (IC(50) > 125 μM). In addition, it was found that QHS induced the activity of CYP3A4 (E(max) 3.5-fold and EC(50) 5.9 μM) and CYP2B6 (E(max) 1.9-fold and EC(50) 0.6 μM). Of the other P450s, UDP glucuronosyltransferases, and transporters studied, QHS and DHA had no significant effect except for minor induction of mRNA expression of CYP1A2 (E(max) 7.9-fold and EC(50) 5.2 μM) and CYP2A6 (E(max) 11.7-fold and EC(50) 4.0 μM) by QHS. Quantitative prediction of P450-mediated DDIs indicate autoinduction of QHS clearance with the AUC(i)/AUC ratio decreasing to 59%, as a result of a 1.9-fold increase in CYP3A4 and a 1.6-fold increase in CYP2B6 activity. These data suggest that QHS drugs are potential inducers of P450 enzymes, and the possible drug interactions (or lack thereof) with artemisinin drugs may be clinically relevant.     

Effects of flavonoids isolated from Scutellariae radix on cytochrome P-450 activities in human liver microsomes

A series of flavonoids isolated from Scutellariae radix were evaluated for their effects on cytochrome P-450 (CYP) activities in human liver microsomes. All flavonoids did not substantially inhibit pentoxyresorufin O-deethylation (CYP2B 1), mephenytoin 4-hydroxylation (CYP2C19), dextromethorphan O-demethylation (CYP2D6), and chlorzoxazone 6-hydroxylation (CYP2E1) activities (IC50: >50 microM). Baicalein and 2',5,6',7-tetrahydroxyflavone inhibited hepatic testosterone 6beta-hydroxylation (CYP3A4) activity with a IC50 of 17.4 and 7.8 microM, respectively. Oroxylin A inhibited diclofenac 4-hydroxylation (CYP2C9) activity with a IC50 of 6.7 microM. In contrast, all flavonoids tested inhibited hepatic caffeine N'-demethylation (CYP1A2) with IC50 values ranging from 0.7 to 51.3 microM. Kinetic analysis revealed that the mechanism of inhibition varied according to the flavonoids. These results suggest that flavonoids tested are inhibitors of hepatic CYP1A2 and that the extracts of Scutellariae radix, widely used as a hepatoprotective agent, may protect the liver through the prevention of CYPIA2-induced metabolic activation of protoxicants.