R/S手性布洛芬的药代动力学相关遗传因素及其在新生儿的应用

布洛芬的药理作用与吲哚美辛相似,为前列腺素合成抑制药物,能关闭早产儿动脉导管。近年来采用布洛芬治疗早产儿动脉导管未闭(patent ductus arteriosus, PDA)疗效好且不良反应明显较少。目前,国内市场上只有口服剂型,并没有静脉注射剂型。布洛芬在其α-碳上存在一个手性中心,具有两种光学对映异构体。临床中常用的布洛芬是手性(S)-(+)布洛芬和(R)-(-)布洛芬的外消旋混合物。但是,不管是在体外还是体内,只有(S)-(+)布洛芬才具有药理活性。约65% 的(R)-(-)布洛芬能在肝脏中转化为(S)-(+)对映体结构。而在人体肠道中,由于存在酰基辅酶A硫酯,(R)-(-)布洛芬能被α-甲基酰基辅酶A消旋酶催化,从而发生单向的手性转化 。     

手性药物和合理用药(续)

2　非甾体抗炎药以布洛芬 (ibuprofen ,7)为例 ,其活性对映体为(S) 对映异构体 ,但临床上用其外消旋体。因为体内低活性的 (R) 布洛芬可以转化为高活性的 (S) 布洛芬。试验表明 ,人体中 70 % (R) 布洛芬可转化为 (S) 布洛芬。因此这类药物体内外的活性比存在很大的差异。虽然体外试验显示这些药物的(S) 对映体的活性是 (R) 对映体的 10～ 10 0倍 ,但体内试验却未观察到如此大的差异。7　　 (R) 布洛芬的体内转化是通过先形成辅酶A(CoA )硫酸酯 ,进而发生由对映体转化的现象[10 ,11] 。由于转化涉及到乙酰CoA参与过程 ,(S) 构…     

反相HPLC间接分离2-芳基丙酸类及结构类似对映体

2-芳基丙酸类化合物(2-APAs)是目前常用的一类非甾体抗炎药,通常以外消旋体上市。体外实验表明药物的S构型有效,R构型几乎无效,但在体内会发生R构型向S构型的代谢手性转换。为研究这种分子构型的转换,需要建立一种能分离对映体并确定其组成的立体选择性分析方法。直接、间接手性色谱法是研究布洛芬构型转化最常用的方法。前人建立的正相HPLC可良好地分离人血中布洛芬的对映体,但不适合分析极性较大的2-APAs,并需先进行2h的衍生化反应。本文报道了一种快速、有效、良好分离2-APAs及类似物的间接反相HPLC方法。仪器　PU4015泵,ISS-…     

立体化学在2-芳基丙酸类非甾体抗炎药临床药物动力学上的重要性

非甾体抗炎药有重大的临床意义。虽然有许多关于非甾体抗炎药临床药物动力学的文献,但只有少数作者考虑2-芳基丙酸类非甾体抗炎药处置的立体化学。2-芳基丙酸处置的独特的特征是不对称中心的代谢手性转化。 2-芳基丙酸的α-碳原子为一手性中心,并已知具活性的药物具有S构型,具R构型者活性低或完全无活性。已报道该系列的几个化合物,如布洛芬和苯噁布洛芬在动物和人体中其手性中心从右旋对映体代谢转变为左旋对映体,而发生代谢激活。这种转化没有涉及化合物的其它代谢转化。     

外消旋普罗帕酮在经诱导的大鼠肝微粒体中N-去丙基化的立体选择性

:采用对照及 β-萘黄酮 (β- NF)或地塞米松(Dex)诱导的大鼠肝微粒体 ,应用 GITC柱前衍生化 ,反相高效液相色谱法研究了消旋普罗帕酮〔(R/S) - PPF〕体外代谢的立体选择性 .实验结果表明 ,在 Dex,β- NF诱导的微粒体中有 N-去丙基普罗帕酮生成。在 β- NF,Dex预处理组 ,(R/S) - PPF低浓度时的经肝微粒体代谢具有立体选择性 ,R(- )对映体的清除大于 S(+)对映体 ,高浓度时的代谢无立体选择性 .R(- )对映体的 Km 值显著低于 S(+)对映体 ,而 Vmax值无显著性差异 .在 Dex预处理组中的立体选择性大于 β- NF组 .在对照组中代谢无立体选择性 ,且 Km,Vmax值均小于β- NF,Dex预处理组。结果提示 ,CYP1 A,CYP3A4亚族对普罗帕酮 (PPF)的 N-去丙基化有贡献 .(R/S) - PPF的N-去丙基化具有浓度依赖性的立体选择性     

3,4-甲撑二氧去氧麻黄碱在生物体内的立体选择性代谢

采用立体选择性分析方法测定了3,4-甲撑二氧去氧麻黄碱在大鼠和小鼠体内0～96h的排泄量。结果表明药物及其代谢物对映体呈现立体选择性的代谢。药物的S-(+)-对映体在N-脱甲基代谢途径中占优势(S/r==1.61),R-(-)-对映体则在O-脱烃基代谢途径中占主导地位(R/S=1.28)。毒性大的S-(+)-对映体代谢较慢;该药物的主体选择性代谢具有种属差异。     

(R)-卤芬酯中S-型对映体的HPLC法测定

建立了HPLC法测定(R)-卤芬酯中S-型对映体.采用Chiralpak AD-H手性色谱柱,以正己烷-异丙醇(90:10)为流动相,检测波长224 nm.(R)-和(S)-卤芬酯均在1～200 μg/ml浓度范围内线性关系良好.回收率为100.1%和99.7%,RSD为1.35%和1.47%.     

布洛芬及其正辛酯对映体的手性高效液相色谱法拆分与应用

目的：建立用于测定有机相中脂肪酶促进布洛芬与正辛醇立体选择性酯化反应转化率及对映体过量值的手性高效液相色谱方法。方法：通过变更流动相组成与配比。找到在Chiralcel OD手性柱上拆分外消旋布洛芬及其正辛酯对映体的最佳色谱条件，建立各自对映体峰面积与浓度之间的校正关系。结果：以100％正己烷作流动相，布洛芬正辛酯的一对对映体可以分开，布洛芬则滞留在柱子上；当在正己烷中添加1％冰醋酸后，布洛芬对映体可以分开，但此时酯的对映体分不开。峰面积－浓度校正曲线表明，布洛芬及其正辛酯各对映体响应因子值相等。结论：可以用峰面积代替浓度，按有关公式算出布洛芬立体选择性酯化反应的转化率及对映体过量值。鉴于冰醋酸对柱子有害等原因，实际样品分析中宜跟踪酯。     

Candida lypolytica脂肪酶催化布洛芬酯对映选择性水解

以国产Candida lypolytica lipase脂肪酶(CLL)为手性催化剂催化布洛芬酯对映选择性水解.研究底物修饰、pH、温度和有机辅溶剂对拆分转化率和对映选择性的影响.CLL催化布洛芬乙酯水解的优势产物为S-布洛芬.在最优反应条件下,转化率30.2%,对映体过量为83.8%.     

普罗帕酮经转人肝CYP3A4基因中国仓鼠CHL细胞代谢的立体选择性

目的:研究普罗帕酮(PPF)经人肝CYP3A4代谢的立体选择性。方法:以转人肝CYP3A4基因中国仓鼠肺细胞CHL的S_9为酶源,考察了PPF消旋体及单个对映体在高、低底物浓度时的经时孵育代谢。对映体抑制试验用于考察对映体之间的相互作用。并进行了单个对映体的酶动力学试验。结果:PPF消旋体高底物浓度(400mg/L)时的代谢无立体选择性,低底物浓度(10mg/L)时R(-)-体代谢快于S( )-体(R>S);单个对映体孵育时在高底物浓度(200mg/L)时的代谢呈现对S( )-体的立体选择性(S>R),低底物浓度(5mg/L)时呈现对R(-)-体的立体选择性(R>S)。S( )-PPF的V_(max)(μmol·mg~(-1)·min~(-1))大于R(-)-体(2.66±0.32 vs 1.71±0.19,P<0.01)。R(-)-PPF的K_m(μmol·L~(-1))小于S( )-体(73±11 vs 185±17,P<0.001)。R(-)-PPF对S( )-体有代谢抑制作用(IC_(50)=125μmol·L~(-1))。结论:PPF经人肝CYP3A4的代谢有底物浓度依赖性的立体选择性。高底物浓度时两对映体有相互作用,相互作用的结果导致立体选择性丧失。而低底物浓度时两对映体无相互作用,结果仍表现出R体代谢优先的立体选择性。     

Studies on the metabolism and chiral inversion of ibuprofen in isolated rat hepatocytes

The oxidative metabolism and chiral inversion of ibuprofen in freshly isolated rat hepatocytes was studied with the aid of a stereoselective GC/MS assay procedure. Hydroxylation of the isobutyl side chain at the subterminal carbon (to give hydroxyibuprofen) proved to be the major route of metabolism of both R(-)-ibuprofen and S(+)-ibuprofen, while formation of the corresponding diastereoisomeric 2-methylpropionic acid derivatives (carboxyibuprofen) was of minor quantitative importance. Both oxidative pathways were inhibited in the presence of metyrapone, a cytochrome P-450 inhibitor. R(-)-Ibuprofen underwent metabolic chiral inversion to the S(+) enantiomer, whose formation was dependent on incubation time, cell density, and substrate concentration. S(+)-Ibuprofen, on the other hand, was not converted to R(-)-ibuprofen in rat hepatocytes. When cells were incubated with a mixture of unlabeled R(-)-ibuprofen and R(-)-[3,3,3-2H3]ibuprofen, the resultant S(+) enantiomer consisted only of unlabeled and trideutero molecules (formed in the same ratio as the corresponding species of R(-)-ibuprofen), indicating that 2,3-dehydroibuprofen did not serve as the symmetrical intermediate in the chiral inversion reaction. Collectively, these results demonstrate that freshly isolated rat hepatocytes represent a convenient and reproducible in vitro model system for studies on the metabolism and chiral inversion of ibuprofen.     

布洛芬精氨酸注射及口服给药在大鼠体内的立体选择性药代动力学

利用手性高效液相色谱法研究大鼠注射及口服布洛芬精氨酸之后布洛芬对映体的药代动力学。布洛芬精氨酸注射及口服给药后, 布洛芬对映体的药代动力学呈现立体选择性, 且口服给药后立体选择性程度更高。与系统前转化相比, R-布洛芬至S-布洛芬的系统转化在口服给药后立体选择性药代动力学中起更重要的作用。布洛芬精氨酸口服给药后, 优势对映体S-布洛芬迅速吸收, S-布洛芬与R-布洛芬的绝对生物利用度分别为100% 和80%。基于研究发现的S-布洛芬体内系统性暴露, 可以推断布洛芬精氨酸注射及口服给药后的药理作用相似, 仅在作用的起始阶段存在差异。     

A novel method for assessing inhibition of ibuprofen chiral inversion and its application in drug discovery

An inhibition assay to assess the potential for chiral inversion of compounds was developed using R(-)-ibuprofen as the probe substrate. Inhibition of the chiral inversion of R(-)-ibuprofen by structurally similar compounds in cyropreserved rat hepatocytes was studied using chiral HPLC and LC/MS methods for the chromatographic separation and detection of enantiomers. Concept validation of this assay was performed with three commercially available compounds and four Pfizer compounds. The results of these studies demonstrated that compounds that are structurally similar to ibuprofen inhibited the formation of S(+)-ibuprofen, suggesting that they may undergo similar enzymatic chiral inversion pathways or compete for the same enzyme active sites. Additionally, an application of this assay in early drug discovery for a specific class of compounds was demonstrated. Thirty-three in-house compounds were screened for their chiral inversion potential utilizing this assay to investigate the structure activity relationship (SAR) for this class of compounds.     

Chiral separation of ibuprofen and chiral pharmacokinetics in healthy Chinese volunteers.

A rapid, sensitive and stereoselective HPLC method based on chiral column analysis was developed and fully validated for the simultaneous determination of the two enantiomers of ibuprofen in human plasma. Using this method, a chiral pharmacokinetic study of two different ibuprofen tablets, i.e. dexibuprofen tablets and racemic ibuprofen tablets, was carried out on 20 healthy Chinese male volunteers according to a single-dose (400 mg), two-way, cross-over randomized design. When a 'non-chiral calculation method' was used, the statistical analysis showed no significant difference for the pharmacokinetic parameters (AUC0-infinity, AUC0-t, Cmax and tmax) between the two oral formulations, suggesting that they were pharmaceutically bioequivalent. Considering that the pharmacological activity of ibuprofen resides exclusively in the S(+)-enantiomer, and that the unidirectional inversion of the R(-) to the S(+)-enantiomer is incomplete and might be race-dependent, the pharmacokinetic parameters for only the S(+)-enantiomer were further compared and the inversion ratio calculated. It was found that only 25% of R(-)-ibuprofen in the racemic ibuprofen tablets was inverted into S(+)-ibuprofen in the Chinese population, which suggested that dexibuprofen might possess a much stronger pharmacological activity than that of racemic ibuprofen when administered at the same dose.     

The effect of competitive and non-linear plasma protein binding on the stereoselective disposition and metabolic inversion of ibuprofen in healthy subjects

The stereoselective disposition and metabolic inversion of ibuprofen were studied in 12 healthy subjects under conditions of competitive and non-linear plasma protein binding. Each subject received each of four oral treatments according to a Latin-square design: 300 mg R(?)-ibuprofen, 300 mg S(+)-ibuprofen, 300 mg R(?)- + 300mg S(+)-ibuprofen, and 300 mg R(?)- + 600 mg S(+)-ibuprofen. For a given treatment, the partial clearance of S(+)-ibuprofen was greater than that of R(?)-ibuprofen for all stereoisomeric drug species. Likewise, the unbound partial clearances of S(+)-ibuprofen were greater for most stereoisomeric drug species. There was also less difference among treatment groups when partial clearances were referenced to unbound as opposed to total plasma concentrations of enantiomer. The unbound intrinsic clearance and fractional inversion of R(?)-ibuprofen were unchanged across the four treatments, and chiral inversion was systemic, averaging 69%. In conclusion, stereoselective differences exist for the partial and composite clearances of R(?)- and S(+)-ibuprofen even when corrected for differences in plasma protein binding. However, differences among treatment groups for a particular elimination pathway are largely due to ibuprofen's non-linear binding.     

Pharmacokinetics of the enantiomers of ibuprofen in the rabbit.

The stereoselective disposition of ibuprofen was studied in male New Zealand White (NZW) rabbits (n = 4) following an infusion (0.16 mg/kg/min) to steady-state of each of the enantiomers of ibuprofen with one week between treatments. The mean (+/- SEM) steady-state clearances of (R)-ibuprofen (15.5 +/- 1.1 ml/min/kg) and (S)-ibuprofen (13.6 +/- 1.9 ml/min/kg) were not significantly different from each other (p greater than 0.05) and exceeded the plasma clearance of indocyanine green (4.3 +/- 0.4 ml/min/kg) in a separate group of rabbits (n = 6). When the infusion rate of the enantiomers was doubled there was a significant decrease in the mean clearance of both (R)-ibuprofen (28%; p less than 0.018) and (S)-ibuprofen (24%; p less than 0.003). There was enantiospecific chiral inversion of (R)-ibuprofen to (S)-ibuprofen (fi = 0.30 +/- 0.07) as has been observed in all species so far studied for this 2-arylpropionic acid. The metabolic capacity for elimination of ibuprofen enantiomers was much greater than reported for either fenoprofen or ketoprofen and suggests that the clearance of ibuprofen enantiomers may be flow dependent in this species.     

Stereoselectivity of ibuprofen metabolism and pharmacokinetics following the administration of the racemate to healthy volunteers

1. The stereoselective metabolism and pharmacokinetics of the enantiomers of ibuprofen have been investigated following the oral administration of the racemic drug (400 mg) to 12 healthy volunteers.2. The stereochemical composition of the drug in serum, both total and unbound, and drug and metabolites, both free and conjugated, in urine were determined by a combination of the direct and indirect chromatographic procedures to enantiomeric analysis. 3. The oral clearance of (S)-ibuprofen was significantly greater than that of the R-enantiomer (74.5 +/- 18.1 versus 57.1 +/- 11.7 ml min(-1); p < 0.05) and the clearance of (R)-ibuprofen via inversion was ca two fold that via alternative pathways. 4. Some 74.0 +/- 9.6% of the dose was recovered in urine over 24 h as ibuprofen, 2-hydroxyibuprofen and carboxyibuprofen, both free and conjugated with glucuronic acid. Analysis of the stereochemical composition of the urinary excretion products indicated that 68% of the dose of (R)-ibuprofen had undergone chiral inversion. 5. Metabolism via glucuronidation and both routes of oxidation, showed enantio-selectivity for (S)-ibuprofen, the enantiomeric ratios (S/R) in partial metabolic clearance being 7.1, 4.8 and 3.4 for formation of ibuprofen glucuronide, 2-hydroxyibuprofen and carboxyibuprofen respectively.6. Modest stereoselectivity was observed in the formation of (2'R, 2R)- and (2'S, 2S)-carboxyibuprofen in comparison to the alternative diastereoisomers, the ratios in formation clearance being 1.6 and 1.2 respectively.     

Stereoselectivity of ibuprofen metabolism and pharmacokinetics following the administration of the racemate to healthy volunteers

1. The stereoselective metabolism and pharmacokinetics of the enantiomers of ibuprofen have been investigated following the oral administration of the racemic drug (400?mg) to 12 healthy volunteers. 2. The stereochemical composition of the drug in serum, both total and unbound, and drug and metabolites, both free and conjugated, in urine were determined by a combination of the direct and indirect chromatographic procedures to enantiomeric analysis. 3. The oral clearance of (S) -ibuprofen was significantly greater than that of the R -enantiomer (74.5 ± 18.1 versus 57.1 ± 11.7 ml?min -1 ; p < 0.05) and the clearance of (R) -ibuprofen via inversion was ca two fold that via alternative pathways. 4. Some 74.0 ± 9.6% of the dose was recovered in urine over 24 h as ibuprofen, 2-hydroxyibuprofen and carboxyibuprofen, both free and conjugated with glucuronic acid. Analysis of the stereochemical composition of the urinary excretion products indicated that 68% of the dose of (R) -ibuprofen had undergone chiral inversion. 5. Metabolism via glucuronidation and both routes of oxidation, showed enantio-selectivity for (S) -ibuprofen, the enantiomeric ratios (S/R) in partial metabolic clearance being 7.1, 4.8 and 3.4 for formation of ibuprofen glucuronide, 2-hydroxyibuprofen and carboxyibuprofen respectively. 6. Modest stereoselectivity was observed in the formation of (2' R, 2 R) - and (2' S, 2 S) -carboxyibuprofen in comparison to the alternative diastereoisomers, the ratios in formation clearance being 1.6 and 1.2 respectively.     

The relationship between the pharmacokinetics of ibuprofen enantiomers and the dose of racemic ibuprofen in humans

Ibuprofen is a chiral drug which is used clinically as a racemate. The pharmacological properties of ibuprofen reside almost exclusively with the S(+)-enantiomer. However, a portion of R(-)-ibuprofen is metabolically inverted to its pharmacologically active, mirror-image form. To investigate the influence of increasing dose of racemic ibuprofen on the pharmacokinetics of its individual enantiomers, four healthy male volunteers were given racemic ibuprofen (200, 400, 800, and 1200 mg), orally, on four occasions. The study was conducted using a balanced cross-over design. The extent of absorption of ibuprofen, as assessed by the total urinary recovery of ibuprofen and its metabolites, was extensive and independent of the administered dose. At all four doses, the area under the total and unbound plasma concentration-time curves (AUC and AUCu, respectively), and the unbound fraction in plasma, were significantly greater for the S(+)-enantiomer. With increasing ibuprofen dose, there was a less than proportional increase in the AUC of each enantiomer, while the AUCu for both enantiomers increased in direct proportion to the administered dose. The time-averaged unbound fraction of each enantiomer increased significantly with increasing dose, which caused the non-linearity between AUC and dose. It was predicted that the metabolic intrinsic clearance of each enantiomer, and the fraction of R(-)-ibuprofen which was metabolically inverted to S(+)-ibuprofen, was independent of the administered dose.     

Renal handling and effects of S(+)-ibuprofen and R(-)-ibuprofen in the rat isolated perfused kidney.

1. The renal handling and effects of S(+)- and R(-)-ibuprofen have been studied in the isolated perfused kidney (IPK) of the rat. 2. Both ibuprofen enantiomers were extensively reabsorbed and accumulated in the kidney in a concentration-dependent manner. No pharmacokinetic differences were observed between the two enantiomers. 3. S(+)-ibuprofen concentrations ranging from 0.25 to 25 micrograms ml-1 (1.2 to 120 microM) caused a decrease in urinary flow, glomerular filtration rate (GFR) and electrolyte excretion. Urinary pH and excretion of glucose were not influenced. R(-)-ibuprofen concentrations ranging from 2.5 to 25 micrograms ml-1 (12 to 120 microM) also decreased urinary flow and electrolyte excretion. This decrease, however, was less than observed with S(+)-ibuprofen. GFR, urinary pH and glucose excretion were not affected by R(-)-ibuprofen. Prostaglandin E2 (PGE2) concentrations of 133 ng ml-1 reversed the effects on renal function of both enantiomers. 4. Very high S(+)- and R(-)-ibuprofen concentrations (greater than 400 micrograms ml-1) resulted in an increase in urinary flow and fractional excretion of sodium, chloride, potassium, glucose and calcium. 5. It is concluded that the pharmacokinetic behaviour of ibuprofen in the kidney is not stereoselective. Relatively high concentrations of both enantiomers increased the urinary flow and electrolyte excretion in a nonstereoselective manner. Lower concentrations of S(+)-ibuprofen decreased urinary flow and electrolyte excretion. The pharmacologically inactive R(-)-ibuprofen was also able to affect renal function in a similar way, but at different concentrations. These effects on renal function are probably caused by inhibition of PGE2 synthesis.