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Drug Metabolism Letters

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https://www.readbyqxmd.com/read/28891437/investigation-of-ocular-bioactivation-potential-and-the-role-of-cytochrome-p450-2d-enzymes-in-rat
#1
Jennifer L Dumouchel, Upendra A Argikar, Jaimie Spear, Ann Brown, Christine E Dunne, Valerie M Kramlinger, Amanda L Cirello, Mithat Gunduz
BACKGROUND: Timolol is clinically administered topically (ocular) to reduce intraocular pressure and treat open-angle glaucoma. Ocular administration of timolol in low doses (0.5% w/v in the form of eye drops) has led to challenges for in vivo metabolite identification. An understanding of drug metabolism in the eye is important for clinical ocular therapeutics and potential drug candidates. METHODS: We aimed to investigate the metabolism of timolol in rat ocular and liver S9 fractions, as well as rat ocular tissue and plasma following a 0...
September 11, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28814243/a-pharmacokinetic-pharmacodynamic-model-of-tamoxifen-and-endoxifen-to-predict-their-distribution-and-effects-on-inhibition-of-tumor-growth
#2
Shengyue Yuan, Qingrong Sun, Yao Chen, Jun Liao
BACKGROUND: Tamoxifen is widely used in the therapy for breast cancer and has three major metabolites, N-desmethyltamoxifen, 4-hydroxytamoxifen, and endoxifen. Endoxifen has played a major role in the inhibition of tumor growth of breast cancer and the tumor growth is related to endoxifen concentration. OBJECTIVES: The aim of this study was to develop a pharmacokinetic-pharmacodynamic model to predict the distribution of tamoxifen and endoxifen quantitatively, and to discover the anti-tumor effect patterns of tamoxifen and endoxifen...
August 15, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28762319/quantification-of-sulfotransferase-1a-isoforms-in-human-tissue-fractions-and-cell-lines-by-multiple-reaction-monitoring-mass-spectrometry
#3
Sho Yoshitake, Melissa McKay-Daily, Masaki Tanaka, Zeqi Huang
BACKGROUND: Within the sulfotransferase (SULT) superfamily of metabolic enzymes, the SULT1A family of cytosolic sulfotransferases is of particular interest, due to its ability to catalyze the sulfation of phenolic substrates. In humans, there are three distinct SULT1A enzymes: SULT1A1, SULT1A2, and SULT1A3/4. OBJECTIVE: To detect and quantify these enzymes in S9 fractions and cell lines using targeted mass spectrometry-based proteomics. METHOD: Samples were tryptically digested, and signature peptides were quantified using liquid chromatography-multiple reaction monitoring mass spectrometry (LC-MRM/MS)...
July 31, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28699487/mixed-matrix-method-provides-a-reliable-metabolite-exposure-comparison-for-assessment-of-metabolite-in-safety-testing-mist
#4
Ryan Takahashi, Cyrus Khojasteh, Matthew Wright, Cornelis Hop, Shuguang Ma
The regulatory guidances on metabolites in safety testing (MIST) by US Food and Drug Administration (FDA) and International Conference on Harmonisation (ICH) describe the necessity to assess exposures of circulating metabolites in humans at steady state relative to exposures achieved in nonclinical safety studies prior to the initiation of large scale clinical trials. This comparison can be accomplished by measuring metabolite concentrations in animals and humans with validated bioanalytical methods. However, bioanalysis of metabolites in multiple species and multiple studies is resource intensive and may impact the timelines of clinical studies...
July 10, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28606035/potential-minor-haplotypes-of-cyp2d6-in-the-japanese-population
#5
Masatoshi Masuda, Tsutomu Fujiwara, Masayuki Matsunaga, Takehisa Matsumaru
BACKGROUND: CYP2D6 is one of the most significant polymorphic genes of drug-metabolizing enzymes due to its association with different metabolic activities and the pharmacokinetics of CYP2D6 substrates. OBJECTIVE: The objective of this study was to explore for a novel haplotype of CYP2D6 in the Japanese population by using a large database of previous clinical studies. METHODS: We analyzed CYP2D6 genotype data from a total of 723 Japanese individuals for 8 loci (100C>T, 1758G>A, 1846G>A, 2573 insertion of C, 2850C>T, 2988G>A, 4125 insertion of 9bp, and 4180G>C) and gene deletion...
June 12, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28595558/the-role-of-placental-carbonyl-reducing-enzymes-in-biotransformation-of-bupropion-and-4-methylnitrosamino-1-3-pyridyl-1-butanone
#6
Valentina M Fokina, Svetlana L Patrikeeva, Cheryl Oncken, Gary Dv Hankins, Mahmoud S Ahmed, Tatiana N Nanovskaya
BACKGROUND: Bupropion (BUP) has a potential to be an effective pharmacotherapy for smoking cessation during pregnancy. Smoking during pregnancy stimulates placental carbonyl reductases that catalyze the biotransformation of BUP. 4-methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) is a potent carcinogen of cigarette smoke. Carbonyl reduction of NNK into 4-methylnitrosamino-1-(3-pyridyl)-1-butanol (NNAL) constitutes a major step in NNK detoxification. Thus, placentas of pregnant smokers on BUP therapy can become a site of drug-drug interaction...
June 6, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28403803/metabolic-profile-of-flunitrazepam-clinical-and-forensic-toxicological-aspects
#7
Ricardo Jorge Dinis-Oliveira
BACKGROUND: Flunitrazepam is a potent hypnotic, sedative, and amnestic drug used to treat insomnia and as a pre-anesthetic agent. The illicit practice in drug-facilitated sexual assault has been implicating important clinical and forensic issues. OBJECTIVE: In this work the metabolism of flunitrazepam was fully reviewed. METHODS: Flunitrazepam and related known metabolizing enzymes and metabolites were searched in books and in PubMed (U.S...
April 7, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28403802/effects-of-fenofibrate-on-the-expression-of-small-heterodimer-partner-shp-and-cytochrome-p450-cyp-2d6
#8
Rebecca Kent, Hyunyoung Jeong
Cytochrome P450 (CYP) 2D6 is a major drug-metabolizing enzyme, responsible for eliminating 25% of marketed drugs. We recently identified SHP as a negative regulator of CYP2D6 expression and showed that factors that alter SHP expression influence CYP2D6 expression. Fenofibrate, an agonist of peroxisome proliferator-activated receptor α (PPARα), has been previously reported to upregulate SHP expression in mouse liver [1]. The objective of this study was to determine whether fenofibrate decreases CYP2D6 expression via upregulating SHP expression...
April 7, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28393714/gender-difference-of-hepatic-and-intestinal-cyp3a4-in-cyp3a-humanized-mice-generated-by-a-human-chromosome-engineering-technique
#9
Kaoru Kobayashi, Chihiro Abe, Mika Endo, Yasuhiro Kazuki, Mitsuo Oshimura, Kan Chiba
BACKGROUND: Cytochrome P450 3A4 (CYP3A4) is an important drug-metabolizing enzyme that is expressed in the liver and small intestine of humans. Various factors influence the expression of CYP3A4, but gender difference in CYP3A4 expression remains debatable. OBJECTIVE: To clarify gender difference of hepatic and intestinal CYP3A4 in CYP3A-humanized mice generated by a human artificial chromosome (HAC) vector system. The CYP3A-humanized (CYP3A-HAC) mice have essential regulatory regions, including promoters and enhancers, and unknown elements affecting the expression of CYP3A4...
April 4, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28332451/inhibitory-effect-of-fruit-juices-on-the-doxorubicin-metabolizing-activity-of-carbonyl-reductase-1
#10
Takeshi Miura, Katsutoshi Nagai, Shingo Kaneshiro, Ayako Taketomi, Toshikatsu Nakabayashi, Hiroki Konishi, Toru Nishinaka, Tomoyuki Terada
BACKGROUND AND OBJECTIVE: Doxorubicin, an anthracycline anti-cancer drug, is effective for breast cancer and childhood lymphoma. Chronic cardiotoxicity has been known as a critical adverse effect of doxorubicin and is attributed to its metabolite doxorubicinol produced by carbonyl reductase 1 (CBR1, SDR21C1). Some flavonoids have been reported to act as inhibitors for CBR1, therefore, commercially available juices containing flavonoids are likely to be applicable as a prophylactic treatment against doxorubicin-induced cardiotoxicity by suppression doxorubicinol production...
March 9, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28260523/obesity-and-inflammation-and-altered-clopidogrel-pharmacokinetics-and-pharmacodynamics
#11
Nicholas B Norgard, Scott V Monte
BACKGROUND: Clopidogrel is a key antiplatelet drug that has substantial interpatient variability in pharmacodynamic response. Patients with lesser degrees of platelet inhibition in response to clopidogrel appear to be at increased risk for cardiovascular events. Obesity is an independent risk factor for cardiovascular morbidity and mortality due to atherothrombotic events and represents a group of patients who are in need of optimized antithrombotic therapy. Central to the obesity-related risk of atherothrombosis is a pro-thrombotic state characterized by increased levels of coagulation factors, impaired fibrinolysis and platelet hyper-reactivity, which results from the interaction among the features clustering in obesity: insulin resistance, inflammation, oxidative stress, and endothelial dysfunction...
March 1, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28137210/the-metabolism-of-methazolamide-in-immortalized-human-keratinocytes-hacat-cells
#12
Tetsuo Sasabe, Shinichiro Maeda, Kenichi Kishida, Mariko Yamano, Yoshihiro Miwa, Toshihiro Sugiyama
OBJECTIVE: Drug therapy is occasionally accompanied by an idiosyncratic severe toxicity, which occurs very rarely, but can lead to patient mortality. Methazolamide, an anti-glaucomatous agent, could cause severe skin eruptions called Stevens-Johnson syndrome/toxic epidermal necrolyis (SJS/TEN). Its precise etiology is still uncertain. In this study, the metabolism of methazolamide was investigated in immortalized human keratinocytes to reveal the possible mechanism which causes SJS/TEN...
January 27, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28103788/pharmacokinetics-metabolism-and-disposition-of-14c-xq-1h-after-intravenous-administration-to-male-rats
#13
Yinlin Qin, Tao Chen, Qiu Jin, Kai Guo, Hao Feng, Dennis Heller, Zheming Gu
This study describes the in vivo pharmacokinetics and metabolism of [14C]labeled XQ-1H in male rats. XQ-1H is a methanesulfonate of XQ, 10-O-(N,N-dimethylaminoethyl)-ginkgolide B is a derivative of ginkgolide B (GB) with enhanced water solubility. Since it is very difficult to synthesize radiolabeled GB, the results obtained in this study may provide helpful insight to further ADME investigation of GB and its analogue compounds. After an i.v. administration of [14C]XQ-1H to male rats, XQ (the freebase form of XQ-1H) was extensively hydrolyzed, moderately metabolized, and mainly excreted in feces (71...
January 18, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28093968/quantification-of-etodolac-in-human-plasma-for-pharmacokinetics-and-bioequivalence-studies-in-27-korean-subjects
#14
Il-Dong Song, Je-Seop Kang, Hyun-Jin Kim, Se-Mi Kim, Dong-Xu Zhao, Shin-Hee Kim, Min-Young Chun, Kyuhyun Lee
We developed a simple and validated liquid chromatography tandem mass spectrometry(LC-MS/MS) for quantification of etodolac using pioglitazone as an internal standard (IS) to assess pharmacokinetics and to appraise bioequivalence of two formulations of etodolac (reference and tested) in 27 healthy Korean subjects. Isocratic mobile phase consisted of 10 mM ammonium formate and acetonitrile were used to separate the analytes on a Gemini C18 column. Also, analytes were analyzed by MS/MS in multiple reaction monitoring (MRM) mode using the transitions of (M+H)+ ions, m/z 288...
January 16, 2017: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28029084/variability-of-zaleplon-5-oxidase-activity-in-mice-and-humans-and-inhibition-by-raloxifene
#15
Chiaki Tanoue, Kazumi Sugihara, Yoshitaka Tayama, Naoto Uramaru, Yoko Watanabe, Shigeru Ohta, Shigeyuki Kitamura
Zaleplon (ZAL) is a sedative-hypnotic agent, which is mainly metabolized to inactive 5-oxidized zaleplon (5-oxo-ZAL) and N-des-ethylated ZAL (des-ethyl-ZAL) in mice and humans. The former reaction is considered to be catalyzed by aldehyde oxidase present in liver cytosol. Here, we examined sex and strain differences of ZAL metabolism to 5-oxo-ZAL among four strains of mice, as well as the inter-individual variation in humans, in order to evaluate the variability of 5-oxo-ZAL-forming activity and its relationship with aldehyde oxidase activity...
December 27, 2016: Drug Metabolism Letters
https://www.readbyqxmd.com/read/28000546/ortho-methylarylamines-as-time-dependent-inhibitors-of-cytochrome-p450-1a1-enzyme
#16
Jayalakshmi Sridhar, Jiawang Liu, Rajesh Komati, Richard Schroeder, Quan Jiang, Phan Tram, Kevin Riley, Maryam Foroozesh
Members of the cytochrome P450 1A family metabolize many procarcinogens such as polycyclic aromatic hydrocarbons and heterocyclic amines. Inactivation of these enzymes is prerequisite for cancer prevention and treatment in certain cases. Mechanism-based inhibition (time and co-factor dependent) is an effective method for the inactivation of these enzymes. Our recent study on emodin analogs revealed an anthraquinone with ortho-methylarylamine moiety that exhibited time-dependent inhibition of P450 enzymes 1A1 and 1A2...
December 20, 2016: Drug Metabolism Letters
https://www.readbyqxmd.com/read/27908259/a-novel-liquid-chromatography-tandem-mass-spectrometry-method-for-the-estimation-of-bilirubin-glucuronides-and-its-application-to-in-vitro-enzyme-assays
#17
Siva Prasad Putluru, Murali Krishna Matta, Deepak Ahire, Murali Subramanian, Michael Sinz, Sandhya Mandlekar
Bilirubin is a toxic waste product of metabolism, eliminated mainly through UGT1A1 mediated conjugation to mono- and di-glucuronides. Due to the potentially low Km value of bilirubin glucuronidation, the quantitative sensitivity obtained with most UV/visible light detection methods are not sufficient to accurately calculate UGT1A1 enzyme kinetics and inhibition properties of new chemical entities at low bilirubin concentrations. In addition, bilirubin, as well as its metabolites, are unstable during sample preparation and bioanalysis...
November 24, 2016: Drug Metabolism Letters
https://www.readbyqxmd.com/read/27842485/cytochrome-p450-2a6-phenotyping-using-dietary-caffeine-salivary-metabolite-ratios-and-genotyping-using-blood-on-storage-cards-in-non-smoking-japanese-volunteers
#18
Norie Murayama, Makiko Shimizu, Kenta KObayashi, Izumi KIshimoto, Hiroshi Yamazaki
BACKGROUND: A simple method of genotyping and phenotyping cytochrome P450 2A6 (CYP2A6) was previously reported using individual blood samples and urinary caffeine metabolite ratios of 1,7-dimethyluric acid (17U) to 1-methylxanthine (1X). OBJECTIVE: Blood spotted onto storage cards and salivary caffeine metabolites were analyzed in 27 healthy non-smoking Japanese volunteers with no prior abstention from dietary caffeine intake. METHODS: 1,7-Dimethylxanthine (17X), 17U, 1X, and caffeine levels in spot saliva samples were determined in Japanese non-smokers by high-performance liquid chromatography under normal dietary caffeine consumption...
November 14, 2016: Drug Metabolism Letters
https://www.readbyqxmd.com/read/27842484/strong-induction-of-cytochrome-p450-1a-3a-but-not-p450-2b-in-cultured-hepatocytes-from-common-marmosets-and-cynomolgus-monkeys-by-typical-human-p450-inducing-agents
#19
Shotaro Uehara, Yasuhiro Uno, Takako Suzuki, Takashi Inoue, Masahiro Utoh, Erika Sasaki, Hiroshi Yamazaki
BACKGROUND: Common marmosets (Callithrix jacchus) and cynomolgus monkeys (Macaca fascicularis) are used as non-human primate models in preclinical studies for drug development. OBJECTIVE: The assessment of P450 induction in hepatocytes from marmosets and cynomolgus monkeys was performed using typical P450 inducers. METHODS: Induction of cytochrome P450 1-4 family enzymes was analyzed in two lots of cultured hepatocytes from common marmosets and cynomolgus monkeys after 24-h treatment with typical human P450 inducing agents by real-time reverse transcription-polymerase chain reaction...
November 14, 2016: Drug Metabolism Letters
https://www.readbyqxmd.com/read/27774888/genipin-inhibits-the-induction-of-inducible-nitric-oxide-synthase-through-the-inhibition-of-nf-%C3%AE%C2%BAb-activation-in-rat-hepatocytes
#20
Richi Nakatake, Takumi Tsuda, Takashi Matsuura, Hirokazu Miki, Hideki Hishikawa, Hideyuki Matsushima, Morihiko Ishizaki, Kosuke Matsui, Masaki Kaibori, Mikio Nishizawa, Tadayoshi Okumura, Masanori Kon
BACKGROUND/AIMS: Genipin is a component of Japanese traditional herbal medicine (Kampo), inchinkoto, and is used for the treatment of various liver injuries. However, there are few scientific evidence for its anti-inflammatory effects and mechanisms. In inflamed liver, proinflammatory cytokines including tumor necrosis factor (TNF)-α and interleukin (IL)-1β stimulate liver cells, followed by the expression of inducible nitric oxide synthase (iNOS). Excessive levels of NO produced by iNOS have been implicated as one of the factors in liver injury...
October 20, 2016: Drug Metabolism Letters
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