Proguanil metabolism in relation to S-mephenytoin oxidation in a Turkish population

The oxidation of proguanil was studied in 89 unrelated healthy Turkish volunteers after administration of proguanil (single dose, 200  mg, orally). Based on the distribution of the ratio of proguanil to cycloguanil excreted in urine, and using an antimode value of 15, the prevalence of poor metabolizers in a Turkish population was estimated to be 5.6% (95% confidence interval 2.0%–17.3%) which was similar to that in the other Caucasian populations. The relationship between the oxidative capacities of CYP2C19 for the two substrates, proguanil and mephenytoin, was studied in 39 subjects (two poor and 37 extensive metabolizers of proguanil). The two poor metabolizers of proguanil were also identified as poor metabolizers of S-mephenytoin and no misclassification by the two phenotyping methods was observed. The correlation between the metabolic ratio of proguanil to cycloguanil and the S/R-mephenytoin ratio as assessed by Spearman's rank test, was statistically significant ( r _s=0.50, P <0.001).     

中国健康志愿者普罗帕酮的药代动力学及与异喹胍，美芬妥英代谢多态性的相关性研究

应用高效液相色谱法及气相色谱法，研究了９名健康志愿者口服单剂量普罗帕酮的药代动力学及与异喹胍，Ｓ－美芬妥英羟化代谢多态性的相关性。结果表明，６名志愿者中普罗帕酮按一房室模型消除，其余３名符合二房室模型。普罗帕酮消除半衰期为３．４±ｓ１．１ｈ，药时曲线下面积为２．５±ｓ１．１μｇ·＝ｍＬ１，血浆清除率为１４５±ｓ６４Ｌ·ｈ１．普罗帕酮药代动力学参数在异喹胍强与弱代谢者中有较大的差异，而与Ｓ－美芬妥英不同羟化代谢表型则无明显相关性．同时服用普罗帕酮和异喹胍时，两药氧化代谢可产生互相抑制性影响．而普罗帕酮与Ｓ－美芬妥英公用则无明显改变，提示普鲁帕酮和异喹胍可能由同一肝微粒体细胞色素Ｐ４５０同工酶所催化代谢     

高蛋白高脂肪高碳水化合物饲料对大鼠地西泮、美芬妥英代谢影响

 目的:研究高蛋白、高脂肪、高碳水化合物饲料对大鼠地西泮、美芬妥英的体内代谢，以了解饮食因素对药牡氧化代谢的影响。方法:HPLC测定用药后不同时间血浆药物及其代谢产物浓度，用3P87程序处理数据，求得药动学参数。结果:与对照组相比，高蛋白饮食使地西浮t _1/2β缩短，AUC降低，Cls增高;使地西浮的代谢产物去甲地西泮的AUC增高;使尿液中S/R-美芬妥英比值明显降低。结论:高蛋白饮食加快地西泮的去甲基化反应，增强S-美芬妥英羟化代谢。     

Gas chromatographic alkylation studies of phenytoin, mephenytoin and primidone: investigation of butylated derivatives

The alkylation of phenytoin, mephenytoin and primidone with n-alkyl iodides in N,N-dimethylacetamide with tetramethylammonium hydroxide was investigated by gas chromatography. With methyl iodide phenytoin and mephenytoin were each converted into a single derivative; the use of other alkyl iodides yielded more than one product. Primidone was converted with methyl iodide and butyl iodide into a major derivative (> 90%) and a minor one. Butylation of the compounds by this method was compared with butylation in an acetone-butyl iodide mixture with potassium carbonate, caesium carbonate or silver oxide added, and with on-column butylation. All these methods resulted in the production of more than one derivative. The derivatives were identified by mass spectrometry and by 1H NMR and 13C NMR. With the acetone-butyl iodide-silver oxide method the main derivatives were O-butylated compounds. The other methods yielded predominantly N-butylated derivatives.     

中国汉族人群S-美芬妥英4'-羟化酶的表型与基因分析

目的：研究中国汉族人群S-美芬妥英4'-羟化代谢遗传多态性。方法：以美芬妥英为探针药物采用手性毛细管气相色谱法测定尿中S-/R-MP浓度比值, 对90名志愿者进行了表型分型测定,应用PCR技术对其中的26名志愿者进行了S-美芬妥英4'-羟化酶（CYP2C19）基因分析。结果：表型分析结果,11人属慢代谢者（PM）,S/R比值0.95;基因分析结果,6人为野生型纯合子（wt/wt）;10人为杂合子（wt/m₁和wt/m₂）,9人为CYP2C19m₁突变型纯合子（m₁/m₁）,1人为两突变型杂合子（m₁/m₂）。结论：表型分析与基因分析结果显示了很好的相关性,本实验测得慢代谢者的频发率为12.2%,与文献报道相符。     

普萘洛尔侧链氧化与S-美芬妥英羟化酶活性间无相关(英文)

目的:了解健康志愿者S-美芬妥英(S-Mep)羟化酶(CYP2C19)与体内普萘洛尔(Pro)侧链氧化能力间的相关性.方法:14名健康的S-Mep强氧化代谢者分批分别口服单剂量消旋Mep 100 mg和消旋Pro 80 mg,分别用气相色谱和液相色谱方法定量分析人尿中S-和R-Mep、4＇-羟基美芬妥英(4＇-OH-M)、萘氧乳酸和人血浆中Pro的浓度.结果:0-8小时尿排泄的S/R比值和4＇-OH-M的1g D％均与Pro侧链氧化的部分代谢清除率不相关(r_s分别为-0.0484和-0.1077).结论:人的CYP2C19不是催化Pro侧链氧化代谢的主要的P-450酶.     

Genetic polymorphisms of drug metabolism

The molecular mechanisms of 3 genetic polymorphisms of drug metabolism have been studied at the level of enzyme activity, enzyme protein and RNA/DNA. As regards debrisoquine/sparteine polymorphism, cytochrome P-450IID6 was absent in livers of poor metabolizers; aberrant splicing of premRNA of P-450IID6 may be responsible for this. Moreover, 3 mutant alleles of the P-450IID6 locus on chromosome 22 associated with the poor metabolizer phenotype were identified by Southern analysis of leucocyte DNA. The presence of 2 identified mutant alleles allowed the prediction of the phenotype in approximately 25% of poor metabolizers. The additional gene-inactivating mutations which are operative in the remainder of poor metabolizers are now being studied. Regarding mephenytoin polymorphism, although the deficient reaction, S-mephenytoin 4'-hydroxylation, has been well defined in human liver microsomes, the mechanism of this polymorphism remains unclear. All antibodies prepared to date against cytochrome P-450 fractions with this activity recognize several structurally similar enzymes and several cDNAs related to these enzymes have been isolated and expressed in heterologous systems. However, which isozyme is affected by this polymorphism is not known. As regards N-acetylation polymorphism, N-acetyltransferases have been purified from human liver, specific antibodies prepared; it was observed that immunoreactive N-acetyltransferase is decreased or undetectable in liver of "slow acetylators". Two genes that encode functional N-acetyltransferase were characterized. The product of one of these genes has identical activity and characteristics as the polymorphic liver enzyme. Cloned DNA from rapid and slow acetylator individuals has been analyzed to identify the structural or regulatory defect that causes deficient N-acetyltransferase.     

Pharmacokinetics and absolute bioavailability of lansoprazole

Objective: In a crossover study 12 healthy volunteers received lansoprazole 15 mg or 30 mg orally, or 15 mg intravenously in randomized order as a single dose. Blood samples were taken and plasma levels of lansoprazole were determined using an HPLC method. The volunteers were phenotyped for the debrisoquine/sparteine and mephenytoin polymorphisms. Results: The total clearance was 517 ml⋅min⁻¹, and the absolute bioavailability was 91% for the 30-mg and 81% for the 15-mg enteric-coated formulation. The elimination half-life was about 1 h. No correlation of the plasma levels to the sparteine metabolic ratio was found, and no correlation to the mephenytoin type could be established, since all volunteers of the mephenytoin type were extensive metabolizers. Although considerable variation, inter- and intraindividually, was observed, the increase in c_max and AUC did not deviate from dose proportionality. The present galenic formulation ensures a high bioavailability after a single dose. Received: 24 March 1995/Accepted in revised form: 11 July 1995     

Cytochrome-P450-dependent hydroxylation in cluster headache

Two isozymes of the cytochrome-P450-dependent drug oxidizing system exhibit polymorphism. Five to 10% of a Caucasian population are deficient in debrisoquine-hydroxylase activity and about 3% in mephenytoin-hydroxylase activity (poor metabolizers). We tested the hypothesis of a possible over-representation of poor metabolizers among patients with cluster headache. The individual metabolic capacity was determined in 30 cluster headache patients after administration of a test dose of 10 mg of debrisoquine and 100 mg of mephenytoin. Two patients (6.7%) were poor metabolizers of debrisoquine and one (3.3%) a poor metabolizer of mephenytoin. This was no different from the rate of poor metabolizers, 7.1% and 3.3% respectively, in a reference panel of healthy Swedish volunteers.