异烟肼与利福平合用致肝毒性增加机制的研究概况

目的:综述抗结核药异烟肼与利福平合用时肝毒性增加机制的研究概况。方法:查询近年来国内外相关报道,综述和分析异烟肼代谢的机制,以及两药合用肝毒性与快慢乙酰化、肝药酶及其他因素的关系。结果:临床研究及动物实验表明异烟肼与利福平二者合用时肝毒性增加有多种论述。结论:利福平可诱导肝药酶加速异烟肼代谢产生肝毒性物质     

利福平与异烟肼联用致肝毒性分析

利福平 (ＲＦＰ)与异烟肼 (ＩＮＨ)二药合用对结核杆菌有协同杀菌作用 ,但二者合用有时出现肝毒性反应 ,现将我们观察的结果分析如下。1　临床资料1 1　一般资料　观察我院住院患者中应用异烟肼、利福平、链霉素 (乙胺丁醇 )三联或异烟肼、利福平、链霉素 (乙胺丁醇 )、吡嗪酰胺四联方案的重症肺结核和肺外结核患者 3 40例 ,男 15 6例 ,女 184例 ,年龄15～ 82岁 ,平均 3 5 .6岁。用药前检查肝功能正常 ,均无丙氨酸转氨酶 (ＡＬＴ)异常史。1 2　药物剂量　ＲＦＰ 45 0～ 60 0ｍｇ ｄ ,ＩＮＨ3 0 0ｍｇ ｄ ,晨起空腹顿服。保肝治疗肝太乐 2 0 …     

利福平／吡嗪酰胺与利福平／异烟肼相比可增加肝毒性

据美国研究者报道 :对潜伏期结核患者短疗程服用利福平 /吡嗪酰胺的毒性更大。为了比较利福平 /吡嗪酰胺和利福平 /异烟肼的疗效 ,研究者对 5 89名ＨＩＶ阳性的潜伏期结核患者进行了多中心预期开放研究。 2 82名接受利福平 6 0 0ｍｇ/ｄ和异烟肼 30 0ｍｇｄ ,疗程 6个月 ,30 7名接受利福平 6 0 0ｍｇ/ｄ和吡嗪酰胺 2 0 0ｍｇ/ (ｋｇ·ｄ) ,疗程 2个月 ,在基线和治疗 1个月后对所有患者测定血肝酶和胆红素水平 ,同时 ,对接受异烟肼的患者 ,3个月后重复测定 ,肝毒性分为 1级(血清ＡＣＴ水平 5 1～ 12 5Ｕ/Ｌ) ,2级 (12 6～ 2 5 0 ) ,3级(2 5 1…     

利福平、异烟肼合用与单用时的肝毒性比较

目的:探讨异烟肼(INH)与利福平(RFP)合用致肝毒性增加的部分作用机制.方法:采用在体心脏灌流法获取小鼠原代 肝细胞,将其常规培养72 h后,含INH(87.5 μmol/L)、RFP(48.6 μmol/L)、INH+RFP(87.5 μmol/L+48.6 μmol/L)培养液培养48 h后,常规HE染色,光镜下观察肝细胞生长情况并计数.结果:INH与RFP合用后与INH单用时比较肝细胞计数减少(P<0.05.P<0.01).结论:RFP和INH合用后使INH肝毒性代谢物浓度增加,可能是其肝毒性增加的原因之一.     

利福平、异烟肼合用与单用时的肝毒性比较

目的:探讨异烟肼(INH)与利福平(RFP)合用致肝毒性增加的部分作用机制.方法:采用在体心脏灌流法获取小鼠原代 肝细胞,将其常规培养72 h后,含INH(87.5 μmol/L)、RFP(48.6 μmol/L)、INH+RFP(87.5 μmol/L+48.6 μmol/L)培养液培养48 h后,常规HE染色,光镜下观察肝细胞生长情况并计数.结果:INH与RFP合用后与INH单用时比较肝细胞计数减少(P<0.05.P<0.01).结论:RFP和INH合用后使INH肝毒性代谢物浓度增加,可能是其肝毒性增加的原因之一.     

白头翁对利福平和异烟肼肝毒性的影响

目的：观察白头翁对利福平、异烟肼致肝毒性的保护作用。方法：分别测定肝损害组和白头翁组小鼠的肝SGPT，肝指数，肝匀浆丙二醛以及肝细胞镜检，并与对照组比较。结果：白头翁组具有对抗利福平、异烟肼引起的SGPT增高和肝自由基的产生，减轻两对肝细胞的损害。肝损害组与对照组和白头翁组比较均有显性差异（P＜0．01）。结论：白头翁对利福平、异烟肼致肝损害具有保护作用。     

山莨菪碱对异烟肼和利福平肝毒性的保护作用

异烟肼和利福平联合用药效果良好,二者为目前结核病短程疗法所必需。但异烟肼和利福平合用肝毒性明显增加。山莨菪碱有保肝作用且有其与抗结核药物联用可降低肝损害的临床报道［１］。本实验就山莨菪碱对异烟肼和利福平肝毒性的保护作用及其机制予以探讨。１　材料和方法１１　动物与用药　昆明种小鼠５０只,♀各半,购自河南医科大学实验动物中心,体重（２１３±１８）ｇ,随机分为５组：Ⅰ组（生理盐水对照组）：生理盐水ｉｐ,００１ｍｌ·ｇ－１,每天１次连用５ｄ;Ⅱ组（肝损伤组）：异烟肼＋利福平,异烟肼（广州明兴制…     

析因设计筛选异烟肼利福平合用致小鼠肝损害的实验方案

目的利用析因设计，筛选利福平(RFP)与异烟肼(INH)合用致小鼠肝损伤的最佳实验方法。方法采用不同的时间(A)、顺序(B)、剂量?给药，分别测定ALT的活性，肝匀浆中GSH及MDA的含量。结果影响两药合用致小鼠肝损害程度的因素依次为：给药剂量、时间和顺序(C>A>B)；最佳给药方法为同时给药10天，RFP与INH均为100mg·Kg^-1·d^-1。结论应用析因设计筛选异烟肼利福平合用致小鼠肝损害的实验方案，能较全面地反映各因素水平对实验的影响，方法可行。     

柑桔素抑制CYP450 3A4活性并减轻异烟肼和利福平合用的肝细胞毒性

目的研究柑桔素对异烟肼和利福平导致肝毒性增加的防治作用及CYP3A4在其中的作用机制。方法将培养的QSG-7701人肝细胞培养液中分别加入异烟肼和利福平,同时加入不同剂量(1、5、25mg.L-1)的柑桔素后继续培养48h。分别收集药物处理后的培养液和细胞,将细胞裂解后,用比色法分别测定培养液和细胞裂解液中的乳酸脱氢酶的活性,计算细胞外和细胞内乳酸脱氢酶的比值。药物处理48h后,将细胞与CYP3A4作用底物咪达唑仑共同孵育2h,采用高效液相色谱质谱联用法测定咪达唑仑浓度的变化,计算细胞内CYP3A4的活性。结果与对照组比较,异烟肼和利福平合用使肝细胞乳酸脱氢酶释放增加,CYP3A4活性增强;5、25mg.L-1的柑桔素均可减弱异烟肼和利福平升高乳酸脱氢酶的作用,但未使其恢复正常水平;5mg.L-1的柑桔素还减弱了异烟肼和利福平合用导致CYP3A4活性增强的作用,但也未使其恢复正常水平。结论异烟肼和利福平合用对人肝细胞具有细胞毒性作用,柑桔素可以通过抑制其升高CYP3A4活性的作用而减轻肝细胞的损伤。     

阿魏酸钠对异烟肼和利福平肝损害小鼠的保护作用

目的：观察阿魏酸钠对异烟肼(INH)和利福平(RFP)肝毒性的保护作用。方法：分别测定血清谷丙转氨酶(ALT)的活性，肝匀浆中谷胱甘肽(GSH)及脂质过氧化物丙二醛(MDA)的含量，肝微粒体中细胞色素P450及其亚型2E1的活性。结果：阿魏酸钠可对抗INH和RFP合用引起的肝指数、血清ALT水平、肝匀浆中的MDA含量，以及细胞色素P450与亚型P450 2E1活性的升高，增加肝匀浆中GSH含量。病理学检查，阿魏酸钠明显减轻肝细胞的变性和坏死。结论：阿魏酸钠时INH和RFP肝毒性的保护作用与保护肝细胞膜、抑制脂质过氧化反应、清除自由基、降低RFP诱导的细胞色素P450酶系统有关。     

番茄红素对异烟肼和利福平致大鼠肝损伤的保护作用

目的观察番茄红素对异烟肼(INH)和利福平(RFP)合用致大鼠肝损伤的保护作用并探讨其作用机制。方法给予异烟肼和利福平(各75mg.kg-1)用药4wk制备肝损伤动物模型,分别给予低、中、高剂量番茄红素(10、20、30mg.kg-1),4wk后测定大鼠血清中AST和ALT含量、肝脏指数,以及肝组织匀浆中的MDA、GSH的含量和SOD的活性,并作肝组织病理学检测。结果番茄红素能降低肝脏指数(P<0.05)、降低大鼠血清AST和ALT的含量、降低大鼠肝匀浆中的MDA、增加肝匀浆中GSH、升高SOD(P<0.05或P<0.01),减轻肝组织变性、坏死程度,缓解肝组织的病理改变。结论番茄红素对INH和RFP合用所致的大鼠肝损伤具有保护作用,其作用机制可能与番茄红素的抗脂质过氧化作用有关。     

An evaluation of potential mechanism-based inactivation of human drug metabolizing cytochromes P450 by monoamine oxidase inhibitors, including isoniazid

AIMS: To characterize potential mechanism-based inactivation (MBI) of major human drug-metabolizing cytochromes P450 (CYP) by monoamine oxidase (MAO) inhibitors, including the antitubercular drug isoniazid. METHODS: Human liver microsomal CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A activities were investigated following co- and preincubation with MAO inhibitors. Inactivation kinetic constants (KI and kinact) were determined where a significant preincubation effect was observed. Spectral studies were conducted to elucidate the mechanisms of inactivation. RESULTS: Hydrazine MAO inhibitors generally exhibited greater inhibition of CYP following preincubation, whereas this was less frequent for the propargylamines, and tranylcypromine and moclobemide. Phenelzine and isoniazid inactivated all CYP but were most potent toward CYP3A and CYP2C19. Respective inactivation kinetic constants (KI and kinact) for isoniazid were 48.6 microm and 0.042 min-1 and 79.3 microm and 0.039 min-1. Clorgyline was a selective inactivator of CYP1A2 (6.8 microm and 0.15 min-1). Inactivation of CYP was irreversible, consistent with metabolite-intermediate complexation for isoniazid and clorgyline, and haeme destruction for phenelzine. With the exception of phenelzine-mediated CYP3A inactivation, glutathione and superoxide dismutase failed to protect CYP from inactivation by isoniazid and phenelzine. Glutathione partially slowed (17%) the inactivation of CYP1A2 by clorgyline. Alternate substrates or inhibitors generally protected against CYP inactivation. CONCLUSIONS: These data are consistent with mechanism-based inactivation of human drug-metabolizing CYP enzymes and suggest that impaired metabolic clearance may contribute to clinical drug-drug interactions with some MAO inhibitors.     

地塞米松的诱导效应对异烟肼大鼠肝毒性的影响

目的观察大鼠孕烷X受体(pregnane X receptor,PXR)激活剂地塞米松(dexamethasone,DEX)对异烟肼(isoniazid,INH)肝毒性的影响,探讨其发生机制,为临床上抗结核药物所致肝损伤的防治策略提供理论依据。方法 SD♂大鼠随机分成4组(n=6):对照组、INH给药组、DEX给药组和INH-DEX合并给药组,分别给予含DEX 20 mg.kg-1的饲料和含1 000 mg.L-1INH的水喂养28 d后,测定肝脏指数(liver index))和药物代谢酶CYP3A活性,并制备肝组织切片观察各组大鼠肝毒性的程度,同时分析血清中酶学指标ALT、AST、ALP和血脂水平。结果使用DEX组的大鼠肝脏指数与对照组相比明显上升(P<0.01),INH合用DEX后肝细胞CYP3A活性与对照组相比增加了近3.0倍(P<0.01),其肝组织损伤程度加剧,肝细胞脂肪变性并伴有大片梗死,血清中ALT、AST、ALP、血脂水平均较单用INH组明显升高。结论大鼠PXR激活剂DEX能增强INH导致的大鼠肝毒性,其机制可能与DEX上调CYP3A的活性有关。     

双环醇对大鼠黄曲霉毒素B1代谢和肝毒性的影响

目的:研究抗肝炎新药双环醇对大鼠黄曲霉毒素B_1(AFB_1)代谢和肝毒性的影响.方法:大鼠灌胃双环醇300 mg·kg~(-1)·d~(-1),连服三日后腹腔注射黄曲霉毒素B_1 1.5 mg·kg~(-1).给黄曲霉毒素B_1 16小时后观察双环醇对黄曲霉毒素B_1引起肝损伤的防护作用以及对体外代谢的影响.结果:双环醇(300 mg·kg~(-1)·d~(-1),连服三日)可明显降低黄曲霉毒素B_1引起的大鼠血清转氨酶和肝脏MDA的升高,增加低毒代谢产物AFQ_1的生成.双环醇还可增加大鼠肝脏细胞色素P450总量和胞浆谷胱甘肽含量,诱导P450 CYP2B1介导的7-戊氧基香豆素脱烃酶和谷胱甘肽疏基转移酶的活性.此外,双环醇对P450 CYP3A介导的红霉素脱甲基酶和 P450 CYP1A介导的7-乙氧基香豆素脱烃酶也有诱导作用.结论:双环醇可通过增加大鼠肝脏对AFB_1代谢的解毒功能起到肝保护作用.     

Identification of the cytochrome P450 enzymes involved in the N-demethylation of sildenafil

AIMS: To characterize the cytochrome P450 (CYP) enzymes responsible for the N-demethylation of sildenafil to its main metabolite, UK-103 320, to investigate the potential inhibitory effects of sildenafil on CYP enzymes and to evaluate the potential of selected drugs to affect sildenafil metabolism. METHODS: The metabolic pathways of sildenafil N-demethylation were studied using human liver microsomes, as well as microsomes expressing individual human CYP enzymes. Further studies to identify the individual enzymes were performed at 2.5 and 250 microM sildenafil, and employed a combination of chemical inhibition, correlation analysis, and metabolism by expressed recombinant CYP enzymes. In addition, the effect of sildenafil on the activity of the six major drug metabolizing enzymes was investigated. RESULTS: Sildenafil conversion was found to be mediated by at least two CYP enzymes, for which the mean kinetic parameters were Km1 = 6(+/-3 microM), Km2 = 81(+/-45 microM), Vmax1 = 22(+/-9 pmol) and Vmax2 = 138(+/-77 pmol) UK-103 320 formed min(-1) mg(-1). At 250 microM sildenafil, N-demethylation was primarily mediated through the low-affinity, high-Km enzyme (approximately 83%), whilst at 2.5 microM there was a greater role for the high-affinity, low-Km enzyme (approximately 61%). Ketoconazole strongly inhibited metabolism at both sildenafil concentrations and was the only significant inhibitor at 250 microM sildenafil. At the lower sildenafil concentration, sulphaphenazole and quinidine also inhibited formation of UK-103 320. Overall, 75% or more of the N-demethylation of sildenafil at any concentration is probably attributable to CYP3A4. These results were supported by experiments using expressed human CYP enzymes, in which only CYP3A4 and CYP2C9 exhibited substantial sildenafil N-demethylase activity (respective Km values of 221 microM and 27 microM). Sildenafil metabolism was inhibited by potent CYP3A4 inhibitors which are used clinically, but was found to be only a weak inhibitor of drug metabolizing enzymes itself, the strongest inhibition occurring against CYP2C9 (Ki = 80 microM). CONCLUSIONS: Evidence is provided for CYP3A4 and to a lesser extent CYP2C9-mediated metabolism of sildenafil. There is the possibility that elevated plasma concentrations of sildenafil could occur with coadministration of known inhibitors of CYP2C9 or CYP3A4. Since peak plasma concentrations of clinical doses of sildenafil are only 200 ng ml(-1) ( approximately 0.4 microM) it is very unlikely that sildenafil will significantly alter the plasma concentration of other compounds metabolized by cytochrome P450 enzymes.     

The xenobiotic inhibitor profile of cytochrome P4502C8

AIMS: To investigate inhibition of recombinant CYP2C8 by: (i) prototypic CYP isoform selective inhibitors (ii) imidazole/triazole antifungal agents (known inhibitors of CYP), and (iii) certain CYP3A substrates (given the apparent overlapping substrate specificity of CYP2C8 and CYP3A). METHODS: CYP2C8 and NADPH-cytochrome P450 oxidoreductase were coexpressed in Spodoptera frugiperda (Sf21) cells using the baculovirus expression system. CYP isoform selective inhibitors, imidazole/triazole antifungal agents and CYP3A substrates were screened for their inhibitory effects on CYP2C8-catalysed torsemide tolylmethylhydroxylation and, where appropriate, the kinetics of inhibition were characterized. The conversion of torsemide to its tolylmethylhydroxy metabolite was measured using an h.p.l.c. procedure. RESULTS: At concentrations of the CYP inhibitor 'probes' employed for isoform selectivity, only diethyldithiocarbamate and ketoconazole inhibited CYP2C8 by > 10%. Ketoconazole, at an added concentration of 10 microM, inhibited CYP2C8 by 89%. Another imidazole, clotrimazole, also potently inhibited CYP2C8. Ketoconazole and clotrimazole were both noncompetitive inhibitors of CYP2C8 with apparent Ki values of 2.5 microM. The CYP3A substrates amitriptyline, quinine, terfenadine and triazolam caused near complete inhibition (82-91% of control activity) of CYP2C8 at concentrations five-fold higher than the known CYP3A Km. Kinetic studies with selected CYP3A substrates demonstrated that most inhibited CYP2C8 noncompetitively. Apparent Ki values for midazolam, quinine, terfenadine and triazolam ranged from 5 to 25 microM. CONCLUSIONS: Inhibition of CYP2C8 occurred at concentrations of ketoconazole and diethyldithiocarbamate normally employed for selective inhibition of CYP3A and CYP2E1, respectively. Some CYP3A substrates have the capacity to inhibit CYP2C8 activity and this may have implications for inhibitory drug interactions in vivo.