1
|
Patocka J, Wu Q, Nepovimova E, Kuca K. Phenytoin - An anti-seizure drug: Overview of its chemistry, pharmacology and toxicology. Food Chem Toxicol 2020; 142:111393. [PMID: 32376339 DOI: 10.1016/j.fct.2020.111393] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Revised: 04/16/2020] [Accepted: 04/24/2020] [Indexed: 12/22/2022]
Abstract
Phenytoin is a long-standing, anti-seizure drug widely used in clinical practice. It has also been evaluated in the context of many other illnesses in addition to its original epilepsy indication. The narrow therapeutic index of phenytoin and its ubiquitous daily use pose a high risk of poisoning. This review article focuses on the chemistry, pharmacokinetics, and toxicology of phenytoin, with a special focus on its mutagenicity, carcinogenicity, and teratogenicity. The side effects on human health associated with phenytoin use are thoroughly described. In particular, DRESS syndrome and cerebellar atrophy are addressed. This review will help in further understanding the benefits phenytoin use in the treatment of epilepsy.
Collapse
Affiliation(s)
- Jiri Patocka
- Faculty of Health and Social Studies, Department of Radiology and Toxicology, University of South Bohemia Ceske Budejovice, Ceske Budejovice, Czech Republic; Biomedical Research Centre, University Hospital, Hradec Kralove, Czech Republic
| | - Qinghua Wu
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic; College of Life Science, Yangtze University, Jingzhou, 434025, China
| | - Eugenie Nepovimova
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic
| | - Kamil Kuca
- Biomedical Research Centre, University Hospital, Hradec Kralove, Czech Republic; Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic.
| |
Collapse
|
2
|
Sasaki E, Yokoi T. Role of cytochrome P450-mediated metabolism and involvement of reactive metabolite formations on antiepileptic drug-induced liver injuries. J Toxicol Sci 2018; 43:75-87. [PMID: 29479037 DOI: 10.2131/jts.43.75] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Several drugs have been withdrawn from the market or restricted to avoid unexpected adverse outcomes. Drug-induced liver injury (DILI) is a serious issue for drug development. Among DILIs, idiosyncratic DILIs have been a serious problem in drug development and clinical uses. Idiosyncratic DILI is most often unrelated to pharmacological effects or the dosing amount of a drug. The number of drugs that cause idiosyncratic DILI continue to grow in part because no practical preclinical tests have emerged that can identify drug candidates with the potential for developing idiosyncratic DILIs. Nevertheless, the implications of drug metabolism-related factors and immune-related factors on idiosyncratic DILIs has not been fully clarified because this toxicity can not be reproduced in animals. Therefore, accumulated evidence for the mechanisms of the idiosyncratic toxicity has been limited to only in vitro studies. This review describes current knowledge of the effects of cytochrome P450 (CYP)-mediated metabolism and its detoxification abilities based on studies of idiosyncratic DILI animal models developed recently. This review also focused on antiepileptic drugs, phenytoin (diphenyl hydantoin, DPH) and carbamazepine (CBZ), which have rarely caused severe adverse reactions, such as fulminant hepatitis, and have been recognized as sources of idiosyncratic DILI. The studies of animal models of idiosyncratic DILIs have produced new knowledge of chronic administration, CYP inductions/inhibitions, glutathione contents, and immune-related factors for the initiation of idiosyncratic DILIs. Considering changes in the drug metabolic profile and detoxification abilities, idiosyncratic DILIs caused by antiepileptic drugs will lead to understanding the mechanisms of these DILIs.
Collapse
Affiliation(s)
- Eita Sasaki
- Department of Safety Research on Blood and Biological Products, National Institute of Infectious Diseases
| | - Tsuyoshi Yokoi
- Department of Drug Safety Sciences, Nagoya University Graduate School of Medicine
| |
Collapse
|
3
|
Kawase A, Tanaka H, Otori T, Matsuyama K, Iwaki M. Effects of duration of phenytoin administration on mRNA expression of cytochrome P450 and P-glycoprotein in the liver and small intestine of rats. Asian J Pharm Sci 2016. [DOI: 10.1016/j.ajps.2016.04.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
|
4
|
Sasaki E, Iwamura A, Tsuneyama K, Fukami T, Nakajima M, Kume T, Yokoi T. Role of cytochrome P450-mediated metabolism and identification of novel thiol-conjugated metabolites in mice with phenytoin-induced liver injury. Toxicol Lett 2015; 232:79-88. [DOI: 10.1016/j.toxlet.2014.10.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Revised: 10/09/2014] [Accepted: 10/09/2014] [Indexed: 11/24/2022]
|
5
|
Hung CC, Huang HC, Gao YH, Chang WL, Ho JL, Chiou MH, Hsieh YW, Liou HH. Effects of polymorphisms in six candidate genes on phenytoin maintenance therapy in Han Chinese patients. Pharmacogenomics 2013; 13:1339-49. [PMID: 22966884 DOI: 10.2217/pgs.12.117] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
AIM The present study aimed to investigate the associations between variants in pharmacokinetic- and pharmacodynamic-related genes with the dosages, concentrations and concentration-dose ratios (CDRs) of phenytoin (PHT). METHODS & RESULTS Eleven genetic polymorphisms in the six candidate genes were detected in 269 epileptic patients under maintenance PHT monotherapy by real-time PCR and PCR-RFLP. Results of a bivariate analysis demonstrated that among tested polymorphisms, carriers of the variant CYP2C9*3 tended to require significantly lower maintenance PHT dosages than wild-type carriers (p < 0.0001); on the other hand, carriers of the variants CYP2C9*3 or CYP2C19*3 revealed significantly higher CDRs than wild-type carriers (p < 0.004). In a further multivariate analysis, variants in SCN1A, CYP2C9, CYP2C19 and ABCB1 genes were significantly associated with CDRs of PHT under adjustment of age, gender and epilepsy classifications (adjusted r(2) = 20.07%). CONCLUSION The results of present study indicated that polygenic analysis may provide useful information in PHT therapy optimization.
Collapse
Affiliation(s)
- Chin-Chuan Hung
- Department of Pharmacy, College of Pharmacy, China Medical University, Taichung, Taiwan
| | | | | | | | | | | | | | | |
Collapse
|
6
|
Saruwatari J, Ishitsu T, Nakagawa K. Update on the Genetic Polymorphisms of Drug-Metabolizing Enzymes in Antiepileptic Drug Therapy. Pharmaceuticals (Basel) 2010; 3:2709-2732. [PMID: 27713373 PMCID: PMC4033946 DOI: 10.3390/ph3082709] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Revised: 08/10/2010] [Accepted: 08/17/2010] [Indexed: 11/30/2022] Open
Abstract
Genetic polymorphisms in the genes that encode drug-metabolizing enzymes are implicated in the inter-individual variability in the pharmacokinetics and pharmaco-dynamics of antiepileptic drugs (AEDs). However, the clinical impact of these polymorphisms on AED therapy still remains controversial. The defective alleles of cytochrome P450 (CYP) 2C9 and/or CYP2C19 could affect not only the pharmacokinetics, but also the pharmacodynamics of phenytoin therapy. CYP2C19 deficient genotypes were associated with the higher serum concentration of an active metabolite of clobazam, N-desmethylclobazam, and with the higher clinical efficacy of clobazam therapy than the other CYP2C19 genotypes. The defective alleles of CYP2C9 and/or CYP2C19 were also found to have clinically significant effects on the inter-individual variabilities in the population pharmacokinetics of phenobarbital, valproic acid and zonisamide. EPHX1 polymorphisms may be associated with the pharmacokinetics of carbamazepine and the risk of phenytoin-induced congenital malformations. Similarly, the UDP-glucuronosyltransferase 2B7 genotype may affect the pharmacokinetics of lamotrigine. Gluthatione S-transferase null genotypes are implicated in an increased risk of hepatotoxicity caused by carbamazepine and valproic acid. This article summarizes the state of research on the effects of mutations of drug-metabolizing enzymes on the pharmacokinetics and pharmacodynamics of AED therapies. Future directions for the dose-adjustment of AED are discussed.
Collapse
Affiliation(s)
- Junji Saruwatari
- Division of Pharmacology and Therapeutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, Oe-honmachi 5-1, Kumamoto 862-0973, Japan.
| | - Takateru Ishitsu
- Kumamoto Saishunso National Hospital, Kumamoto, Suya 2659, Koshi, Japan.
| | - Kazuko Nakagawa
- Division of Pharmacology and Therapeutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, Oe-honmachi 5-1, Kumamoto 862-0973, Japan.
- Center for Clinical Pharmaceutical Sciences, Kumamoto University, Oe-honmachi 5-1, Kumamoto 862-0973, Japan.
| |
Collapse
|
7
|
Zhou SF, Liu JP, Chowbay B. Polymorphism of human cytochrome P450 enzymes and its clinical impact. Drug Metab Rev 2009; 41:89-295. [PMID: 19514967 DOI: 10.1080/03602530902843483] [Citation(s) in RCA: 502] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Pharmacogenetics is the study of how interindividual variations in the DNA sequence of specific genes affect drug response. This article highlights current pharmacogenetic knowledge on important human drug-metabolizing cytochrome P450s (CYPs) to understand the large interindividual variability in drug clearance and responses in clinical practice. The human CYP superfamily contains 57 functional genes and 58 pseudogenes, with members of the 1, 2, and 3 families playing an important role in the metabolism of therapeutic drugs, other xenobiotics, and some endogenous compounds. Polymorphisms in the CYP family may have had the most impact on the fate of therapeutic drugs. CYP2D6, 2C19, and 2C9 polymorphisms account for the most frequent variations in phase I metabolism of drugs, since almost 80% of drugs in use today are metabolized by these enzymes. Approximately 5-14% of Caucasians, 0-5% Africans, and 0-1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant enzyme that demonstrates multiple genetic variants with a potentially functional impact on the efficacy and adverse effects of drugs that are mainly eliminated by this enzyme. Studies into the CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and *3 alleles. Extensive polymorphism also occurs in other CYP genes, such as CYP1A1, 2A6, 2A13, 2C8, 3A4, and 3A5. Since several of these CYPs (e.g., CYP1A1 and 1A2) play a role in the bioactivation of many procarcinogens, polymorphisms of these enzymes may contribute to the variable susceptibility to carcinogenesis. The distribution of the common variant alleles of CYP genes varies among different ethnic populations. Pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and currently available drugs. Further studies are warranted to explore the gene-dose, gene-concentration, and gene-response relationships for these important drug-metabolizing CYPs.
Collapse
Affiliation(s)
- Shu-Feng Zhou
- School of Health Sciences, RMIT University, Bundoora, Victoria, Australia.
| | | | | |
Collapse
|
8
|
Zhou SF, Zhou ZW, Huang M. Polymorphisms of human cytochrome P450 2C9 and the functional relevance. Toxicology 2009; 278:165-88. [PMID: 19715737 DOI: 10.1016/j.tox.2009.08.013] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Revised: 08/18/2009] [Accepted: 08/21/2009] [Indexed: 12/19/2022]
Abstract
Human cytochrome P450 2C9 (CYP2C9) accounts for ∼20% of hepatic total CYP content and metabolizes ~15% clinical drugs such as phenytoin, S-warfarin, tolbutamide, losartan, and many nonsteroidal anti-inflammatory agents (NSAIDs). CYP2C9 is highly polymorphic, with at least 33 variants of CYP2C9 (*1B through *34) being identified so far. CYP2C9*2 is frequent among Caucasians with ~1% of the population being homozygous carriers and 22% are heterozygous. The corresponding figures for the CYP2C9*3 allele are 0.4% and 15%, respectively. There are a number of clinical studies addressing the impact of CYP2C9 polymorphisms on the clearance and/or therapeutic response of therapeutic drugs. These studies have highlighted the importance of the CYP2C9*2 and *3 alleles as a determining factor for drug clearance and drug response. The CYP2C9 polymorphisms are relevant for the efficacy and adverse effects of numerous NSAIDs, sulfonylurea antidiabetic drugs and, most critically, oral anticoagulants belonging to the class of vitamin K epoxide reductase inhibitors. Warfarin has served as a practical example of how pharmacogenetics can be utilized to achieve maximum efficacy and minimum toxicity. For many of these drugs, a clear gene-dose and gene-effect relationship has been observed in patients. In this regard, CYP2C9 alleles can be considered as a useful biomarker in monitoring drug response and adverse effects. Genetic testing of CYP2C9 is expected to play a role in predicting drug clearance and conducting individualized pharmacotherapy. However, prospective clinical studies with large samples are warranted to establish gene-dose and gene-effect relationships for CYP2C9 and its substrate drugs.
Collapse
Affiliation(s)
- Shu-Feng Zhou
- School of Health Sciences, RMIT University, Victoria 3083, Australia.
| | | | | |
Collapse
|
9
|
Tutor‐Crespo MJ, Hermida J, Tutor JC. Phenytoin immunoassay measurements in serum samples from patients with renal insufficiency: comparison with high-performance liquid chromatography. J Clin Lab Anal 2007; 21:119-23. [PMID: 17385679 PMCID: PMC6649125 DOI: 10.1002/jcla.20115] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The debate continues regarding the possible interference of phenytoin metabolites in phenytoin immunoassays, and its clinical importance for patients with renal failure. The aim of this study was to compare the results obtained using the Abbott fluorescence polarization immunoassay (FPIA), Dade enzyme-multiplied immunoassay technique (EMIT), and high-performance liquid chromatography (HPLC) to establish the significance of the differences in conditions of renal failure. Thirty-six adult patients who had been treated with phenytoin and whose renal function ranged from normal to severely impaired were chosen for this study. In accordance with previously established validation criteria for analytical methods for the determination of drugs, a 15% bias from the HPLC phenytoin values was considered an acceptable limit. The mean (+/-SEM) glomerular filtration rate (GFR) of the patients was 37.5+/-4.6 mL/min (range = 10-102 mL/min). The mean values found using FPIA (10.8+/-1.2 microg/mL) and EMIT (10.8+/-1.3 microg/mL) presented acceptable deviations with respect to HPLC (10.5+/-1.2 microg/mL), and a high correlation was found among the results (N = 36) of the different methods (r > or = 0.987, P < 0.001). An FPIA deviation above the 15% bias limit with respect to HPLC was found only in two cases with very low serum phenytoin concentrations and low GFR values (< 20 mL/min), although it does not appear to be important in terms of adjusting drug dosage. According to our data, FPIA and EMIT gave accurate results for total phenytoin in serum samples from patients with renal failure.
Collapse
Affiliation(s)
| | - Jesús Hermida
- Laboratorio Central, Hospital Clínico Universitario, Santiago de Compostela, Spain
| | - J. Carlos Tutor
- Laboratorio Central, Hospital Clínico Universitario, Santiago de Compostela, Spain
| |
Collapse
|
10
|
Zhou S, Chan E, Duan W, Huang M, Chen YZ. Drug bioactivation, covalent binding to target proteins and toxicity relevance. Drug Metab Rev 2005; 37:41-213. [PMID: 15747500 DOI: 10.1081/dmr-200028812] [Citation(s) in RCA: 197] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A number of therapeutic drugs with different structures and mechanisms of action have been reported to undergo metabolic activation by Phase I or Phase II drug-metabolizing enzymes. The bioactivation gives rise to reactive metabolites/intermediates, which readily confer covalent binding to various target proteins by nucleophilic substitution and/or Schiff's base mechanism. These drugs include analgesics (e.g., acetaminophen), antibacterial agents (e.g., sulfonamides and macrolide antibiotics), anticancer drugs (e.g., irinotecan), antiepileptic drugs (e.g., carbamazepine), anti-HIV agents (e.g., ritonavir), antipsychotics (e.g., clozapine), cardiovascular drugs (e.g., procainamide and hydralazine), immunosupressants (e.g., cyclosporine A), inhalational anesthetics (e.g., halothane), nonsteroidal anti-inflammatory drugs (NSAIDSs) (e.g., diclofenac), and steroids and their receptor modulators (e.g., estrogens and tamoxifen). Some herbal and dietary constituents are also bioactivated to reactive metabolites capable of binding covalently and inactivating cytochrome P450s (CYPs). A number of important target proteins of drugs have been identified by mass spectrometric techniques and proteomic approaches. The covalent binding and formation of drug-protein adducts are generally considered to be related to drug toxicity, and selective protein covalent binding by drug metabolites may lead to selective organ toxicity. However, the mechanisms involved in the protein adduct-induced toxicity are largely undefined, although it has been suggested that drug-protein adducts may cause toxicity either through impairing physiological functions of the modified proteins or through immune-mediated mechanisms. In addition, mechanism-based inhibition of CYPs may result in toxic drug-drug interactions. The clinical consequences of drug bioactivation and covalent binding to proteins are unpredictable, depending on many factors that are associated with the administered drugs and patients. Further studies using proteomic and genomic approaches with high throughput capacity are needed to identify the protein targets of reactive drug metabolites, and to elucidate the structure-activity relationships of drug's covalent binding to proteins and their clinical outcomes.
Collapse
Affiliation(s)
- Shufeng Zhou
- Department of Pharmacy, Faculty of Science, National University of Singapore, Singapore.
| | | | | | | | | |
Collapse
|
11
|
Nakajima M, Sakata N, Ohashi N, Kume T, Yokoi T. Involvement of multiple UDP-glucuronosyltransferase 1A isoforms in glucuronidation of 5-(4'-hydroxyphenyl)-5-phenylhydantoin in human liver microsomes. Drug Metab Dispos 2002; 30:1250-6. [PMID: 12386132 DOI: 10.1124/dmd.30.11.1250] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In humans, orally administered phenytoin, 5,5-diphenylhydantoin, is mainly excreted as 5-(4'-hydroxyphenyl)-5-phenylhydantoin (4'-HPPH) O-glucuronide. Phenytoin is oxidized to 4'-HPPH by CYP2C9 and to a minor extent by CYP2C19, and then 4'-HPPH is metabolized to 4'-HPPH O-glucuronide by UDP-glucuronosyltransferase (UGT). In the present study, 4'-HPPH O-glucuronidation in human liver microsomes was investigated. The metabolite formed by incubation with human liver microsomes, 4'-HPPH, and UDP-glucuronic acid was identified as 4'-HPPH O-glucuronide by liquid chromatography-tandem mass spectrometry analysis. The 4'-HPPH O-glucuronosyltransferase activity in human liver microsomes was not saturated at concentrations up to 500 microM of 4'-HPPH. Any commercially available recombinant human UGTs (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B7, and UGT2B15) expressed in baculovirus-infected insect cells did not show detectable 4'-HPPH O-glucuronide. The 4'-HPPH O-glucuronidation in pooled human liver microsomes was inhibited by beta-estradiol as a typical substrate for UGT1A1 (IC(50) = 21.1 microM) and imipramine as a typical substrate for UGT1A4 (IC(50) = 57.7 microM). The inhibitory effects of propofol as a specific substrate for UGT1A9 (IC(50) = 167.1 microM) and emodin as a substrate for UGT1A8 and UGT1A10 (IC(50) = 287.6 microM) were not prominent. The interindividual difference in the 4'-HPPH O-glucuronidation in 14 human liver microsomes was 28.5-fold (0.023-0.656 nmol/min/mg of protein). The 4'-HPPH O-glucuronosyltransferase activity in 11 human liver microsomes was significantly (r = 0.609, P < 0.05) correlated with the 4-nitrophenol glucuronosyltransferase activity, which is catalyzed by UGT1A6 and UGT1A9. These results suggest that multiple UGT1As such as UGT1A1, UGT1A4, UGT1A6, and UGT1A9 are involved in 4'-HPPH O-glucuronidation in human liver microsomes, although the percentage contribution of each UGT1A could not be estimated. Large interindividual differences in the glucuronidation of 4'-HPPH might be responsible for the nonlinearity of the phenytoin plasma concentration or adverse reactions in humans.
Collapse
Affiliation(s)
- Miki Nakajima
- Division of Drug Metabolism, Faculty of Pharmaceutical Sciences, Kanazawa University, Kanazawa, Japan
| | | | | | | | | |
Collapse
|
12
|
Komatsu T, Yamazaki H, Nakajima M, Yokoi T. Identification of catalase in human livers as a factor that enhances phenytoin dihydroxy metabolite formation by human liver microsomes. Biochem Pharmacol 2002; 63:2081-90. [PMID: 12110367 DOI: 10.1016/s0006-2952(02)01024-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have reported previously that the formation of a 3',4'-dihydroxylated metabolite of phenytoin (3',4'-diHPPH) by human liver microsomal cytochrome P450 (P450) is enhanced by the addition of human liver cytosol [Komatsu et al., Drug Metab Dispos 2000;28:1361-8]. The enhancing factor was determined in this study. The addition of cytosolic proteins precipitated by 50% ammonium sulfate to incubation mixtures increased the rate of microsomal 3',4'-diHPPH formation. This fraction was separated further by diethylaminoethyl-, carboxymethyl-, and hydroxyapatite-column chromatography. The amino acid sequence of the purified protein of approximately 55kDa by electrophoresis revealed this protein to be a catalase. The addition of purified or authentic catalase to the incubation mixtures increased the rates of microsomal 3',4'-diHPPH formation from 3'- and 4'-hydroxylated metabolites and from phenytoin in a concentration-dependent manner. In reconstituted systems containing CYP2C9, CYP2C19, and CYP3A4, the formation of 3',4'-diHPPH was also enhanced by catalase to different extents. This is the first report that catalase in livers enhances drug oxidation activities catalyzed by P450 in human liver microsomes.
Collapse
Affiliation(s)
- Tomoko Komatsu
- Division of Drug Metabolism, Faculty of Pharmaceutical Sciences, Kanazawa University, Kanazawa, Japan
| | | | | | | |
Collapse
|
13
|
Miyata M, Motoki K, Tamura E, Furukawa M, Gonzalez FJ, Yamazoe Y. Relative importance of maternal and embryonic microsomal epoxide hydrolase in 7,12-dimethylbenz[a]anthracene-induced developmental toxicity. Biochem Pharmacol 2002; 63:1077-84. [PMID: 11931840 DOI: 10.1016/s0006-2952(02)00847-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Microsomal epoxide hydrolase (mEH) catalyzes the hydrolysis of epoxide intermediates derived from drugs and environmental chemicals. The response of in vivo (embryo) and in vitro (embryo fibroblast) tests were analyzed using mEH-null and wild-type mice to determine the relative role of maternal and embryonic mEH in the developmental toxicity induced by 7,12-dimethylbenz[a]anthracene (DMBA). Embryos derived from DMBA-treated [50mg/kg, daily from gestational day (GD) 11 to GD 15] dams were analyzed. Although weight (P=0.0009) and crown-rump length (P=0.0003) of wild-type fetuses on GD 18 were significantly lower than those of mEH-null fetuses, respectively, no significant difference was found between mEH-null and heterozygous fetuses of mEH-null dams. Cell viability was decreased to 50% in wild-type mouse embryo fibroblasts (MEFs) treated with 3 microM DMBA, but no significant decrease was found in mEH-null MEFs. DMBA-3,4-diol produced a significant decrease in cell viability and suppressed the proliferation of wild-type MEFs at a 10-fold lower concentration than did DMBA. Although mEH protein was expressed in liver microsomes from wild-type embryos (GD 15), DMBA-3,4-diol was not detected among the DMBA metabolites. However, it was detected in the serum of wild-type pregnant mice treated with DMBA, but not in that of mEH-null mice. These results suggest that maternal mEH plays a major role in DMBA-induced developmental toxicity, and embryonic mEH is less involved in the toxicity.
Collapse
MESH Headings
- 9,10-Dimethyl-1,2-benzanthracene/analogs & derivatives
- 9,10-Dimethyl-1,2-benzanthracene/analysis
- 9,10-Dimethyl-1,2-benzanthracene/metabolism
- 9,10-Dimethyl-1,2-benzanthracene/toxicity
- Analysis of Variance
- Animals
- Carcinogens/metabolism
- Carcinogens/toxicity
- Cell Survival/drug effects
- Embryo, Mammalian/cytology
- Embryo, Mammalian/drug effects
- Embryo, Mammalian/enzymology
- Epoxide Hydrolases/metabolism
- Fibroblasts/drug effects
- Mice
- Mice, Inbred C57BL
Collapse
Affiliation(s)
- Masaaki Miyata
- Division of Drug Metabolism and Molecular Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
| | | | | | | | | | | |
Collapse
|
14
|
Guan F, Uboh CE, Soma LR, Birks EK, Teleis D, Rudy JA, Watson AO, Tsang DS. Quantification of phenytoin and its metabolites in equine plasma and urine using high-performance liquid chromatography. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 2000; 746:209-18. [PMID: 11076073 DOI: 10.1016/s0378-4347(00)00330-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A reliable and sensitive method for the extraction and quantification of phenytoin (5,5'-diphenylhydantoin), its major metabolite, 5-(p-hydroxyphenyl)-5-phenylhydantoin (p-HPPH) and minor metabolite, 5-(m-hydroxyphenyl)-5-phenylhydantoin (m-HPPH) in horse urine and plasma is described. The method involves the use of solid-phase extraction (SPE), liquid-liquid extraction (LLE), enzyme hydrolysis (EH) and high-performance liquid chromatography (HPLC). The minor metabolite, 5-(m-hydroxyphenyl)-5-phenylhydantoin (m-HPPH) was not present in a reliably quantifiable concentration in all samples. The new method described was successfully applied in the pharmacokinetic studies and elimination profile of phenytoin and p-HPPH following oral or intravenous administration in the horse.
Collapse
Affiliation(s)
- F Guan
- University of Pennsylvania School of Veterinary Medicine Department of Clinical Studies, Kennett Square 19348, USA
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Cloyd JC, Remmel RP. Antiepileptic drug pharmacokinetics and interactions: impact on treatment of epilepsy. Pharmacotherapy 2000; 20:139S-151S. [PMID: 10937813 DOI: 10.1592/phco.20.12.139s.35255] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
An understanding of epilepsy therapy's pharmacokinetic and drug interaction principles-combined with knowledge of antiepileptic drug (AED) clinical pharmacology-allows more effective use of these drugs. The most desirable pharmacokinetic characteristic is a linear relationship between dose and steady-state concentration, as this determines the ease or difficulty in determining the appropriate dose. Drug-drug interactions affecting AED metabolism are common, clinically important, and, until recently, often unpredictable. Advances in molecular biology have identified specific enzymes responsible for AED metabolism and interactions. Clinicians now can identify potential interactions and avoid or manage them by adjusting drug dosage. Most newer AEDs follow or approximate linear pharmacokinetics, are absorbed extensively and consistently, are not significantly bound to plasma proteins, do not form active metabolites, and have few, if any, drug interactions. In cases where interactions occur between newer AEDs and other drugs, knowledge of these interactions reduces the likelihood of serious adverse events. The pharmacokinetics of the newer AEDs simplify drug dosing and monitoring and should lead to improved patient care.
Collapse
Affiliation(s)
- J C Cloyd
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis 55455, USA
| | | |
Collapse
|
16
|
Abstract
Hypersensitivity reactions to the aromatic antiepileptic drugs (AEDs) phenytoin (PHT) and carbamazepine (CBZ) appear to have an immune etiology. Current models of drug hypersensitivity center around the concept of drug bioactivation to reactive metabolites that irreversibly modify cellular proteins. These modified proteins are believed to initiate (or serve as targets of) an autoimmune-like attack on specific drug-modified proteins in target organs (e.g., liver, skin) of susceptible individuals. Consistent with this model, antibodies to drug-modified and native proteins have been identified in the sera of patients experiencing several drug hypersensitivity reactions. New models must incorporate an understanding of the mechanisms by which drug-modified proteins are processed and presented to the immune system in the appropriate context to culminate in the clinical manifestations of "hypersensitivity." Idiosyncratic toxicities associated with new AEDs, such as lamotrigine and felbamate, appear mechanistically distinct from PHT and CBZ hypersensitivity but may involve similar processes: bioactivation, detoxification, covalent adduct formation, processing and presentation of antigen to the immune system, and consequent formation of antibody and T-cell immune effectors. The goal of research is to develop a "susceptibility profile" for identifying individuals at risk for these forms of drug toxicity.
Collapse
Affiliation(s)
- J S Leeder
- The Children's Mercy Hospital, Department of Pediatrics, University of Missouri-Kansas City, 64108, USA
| |
Collapse
|
17
|
Mays DC, Pawluk LJ, Apseloff G, Davis WB, She ZW, Sagone AL, Gerber N. Metabolism of phenytoin and covalent binding of reactive intermediates in activated human neutrophils. Biochem Pharmacol 1995; 50:367-80. [PMID: 7646538 DOI: 10.1016/0006-2952(95)00151-o] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
ontivation of neutrophils by phorbol-12-myristate-13-acetate (PMA) causes rapid production of superoxide radical (O2-), leading to the formation of additional reactive oxygen species, including hydrogen peroxide (H2O2), hypochlorous acid (HOCl), and possibly hydroxyl radical (.OH). These reactive oxygen species have been associated with the oxidation of some drugs. We investigated the metabolism of phenytoin (5,5-diphenylhydantoin) and the covalent binding of reactive intermediates to cellular macromolecules in activated neutrophils. In incubations with 100 microM phenytoin, PMA-stimulated neutrophils from six human subjects produced p-, m-, and o-isomers of 5-(hydroxyphenyl)-5-phenylhydantoin (HPPH) in a ratio of 1.0:2.1:2.8, respectively, as well as unidentified polar products. Analysis of cell pellets demonstrated that phenytoin was bioactivated to reactive intermediates that bound irreversibly to macromolecules in neutrophils. Glutathione, catalase, superoxide dismutase, azide, and indomethacin all diminished the metabolism of phenytoin and the covalent binding of its reactive intermediates. The iron-inactivating chelators desferrioxamine and diethylenetriaminepentaacetic acid had little or no effect on the metabolism of phenytoin by neutrophils, demonstrating that adventitious iron was not contributing via Fenton chemistry. In an .OH-generating system containing H2O2 and Fe2+ chelated with ADP, phenytoin was oxidized rapidly to unidentified polar products and to p-, m-, and o-HPPH (ratio 1.0:1.7:1.5, respectively). Reagent HOCl and human myeloperoxidase (MPO), in the presence of Cl- and H2O2, both formed the reactive dichlorophenytoin but no HPPH. However, no chlorinated phenytoin was detected in activated neutrophils, possibly because of its high reactivity. These findings, which demonstrated that activated neutrophils biotransform phenytoin in vitro to hydroxylated products and reactive intermediates that bind irreversibly to tissue macromolecules, are consistent with phenytoin hydroxylation by .OH generated by a transition metal-independent process, chlorination by HOCl generated by MPO, and possibly cooxidation by neutrophil hydroperoxidases. Neutrophils activated in vivo may similarly convert phenytoin to reactive intermediates, which could contribute to some of the previously unexplained adverse effects of the drug.
Collapse
Affiliation(s)
- D C Mays
- Department of Pharmacology, Ohio State University, Columbus 43210, USA
| | | | | | | | | | | | | |
Collapse
|
18
|
Edeki TI, Brase DA. Phenytoin disposition and toxicity: role of pharmacogenetic and interethnic factors. Drug Metab Rev 1995; 27:449-69. [PMID: 8521750 DOI: 10.3109/03602539508998331] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- T I Edeki
- Department of Pharmacology, Meharry Medical College, Nashville, TN 37208, USA
| | | |
Collapse
|
19
|
Eadie MJ, McKinnon GE, Dickinson RG, Hooper WD, Lander CM. Phenytoin metabolism during pregnancy. Eur J Clin Pharmacol 1992; 43:389-92. [PMID: 1451718 DOI: 10.1007/bf02220614] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The steady-state 72 h urinary excretion of various phenytoin metabolites has been measured in 10 epileptic women, whose plasma phenytoin concentrations relative to the phenytoin dose fell during pregnancy and rose again post-partum. In later pregnancy and post partum, a mean of 61.3% and 48.9%, respectively, of the total daily phenytoin dose was eliminated as 5-(4-hydroxyphenyl)-5-phenylhydantoin (p-HPPH). Even though p-HPPH accounts for not much more than half the total daily phenytoin dose, increased excretion of this metabolite sufficed to account for the elimination of the entire increase in the dose of phenytoin required during pregnancy. There was no definite increase in the excretion of any other (minor) metabolite measured. Thus pregnancy seems not to enhance uniformly the capacity of the various metabolic pathways of phenytoin.
Collapse
Affiliation(s)
- M J Eadie
- Department of Medicine, University of Queensland, Royal Brisbane Hospital, Australia
| | | | | | | | | |
Collapse
|
20
|
Abstract
This review discussed various analytical methods for the determination of antiepileptic drugs and their metabolites in biological tissues. The emphasis was on the reports published since their last review [J. T. Burke and J. P. Thenot, J. Chromatogr., 340 (1985) 199]. Both chromatographic and immunological procedure were cited and compared. Methods for individual and simultaneous quantitation of standard antiepileptic drugs and their metabolites were considered. In addition, a discussion of free drug determination and procedures for new candidate antiepileptic drugs were included.
Collapse
Affiliation(s)
- I M Kapetanovic
- Preclinical Pharmacology Section, NINDS, NIH, Bethesda, MD 20892
| |
Collapse
|