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Xiong Y, Shi Q, Smith A, Schlenk D, Gan J. Methylation and Demethylation of Emerging Contaminants Changed Bioaccumulation and Acute Toxicity in Daphnia magna. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:15213-15222. [PMID: 37769124 PMCID: PMC10569044 DOI: 10.1021/acs.est.3c03242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 09/13/2023] [Accepted: 09/15/2023] [Indexed: 09/30/2023]
Abstract
Contaminants of emerging concern (CECs) in the environment undergo various transformations, leading to the formation of transformation products (TPs) with a modified ecological risk potential. Although the environmental significance of TPs is increasingly recognized, there has been relatively little research to understand the influences of such transformations on subsequent ecotoxicological safety. In this study, we used four pairs of CECs and their methylated or demethylated derivatives as examples to characterize changes in bioaccumulation and acute toxicity in Daphnia magna, as a result of methylation or demethylation. The experimental results were further compared to quantitative structure-activity relationship (QSAR) predictions. The methylated counterpart in each pair generally showed greater acute toxicity in D. magna, which was attributed to their increased hydrophobicity. For example, the LC50 values of methylparaben (34.4 ± 4.3 mg L-1) and its demethylated product (225.6 ± 17.3 mg L-1) differed about eightfold in D. magna. The methylated derivative generally exhibited greater bioaccumulation than the demethylated counterpart. For instance, the bioaccumulation of methylated acetaminophen was about 33-fold greater than that of acetaminophen. In silico predictions via QSARs aligned well with the experimental results and suggested an increased persistence of the methylated forms. The study findings underline the consequences of simple changes in chemical structures induced by transformations such as methylation and demethylation and highlight the need to consider TPs to achieve a more holistic understanding of the environmental fate and risks of CECs.
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Affiliation(s)
- Yaxin Xiong
- Department of Environmental
Sciences, University of California, Riverside, California 92521, United States
| | - Qingyang Shi
- Department of Environmental
Sciences, University of California, Riverside, California 92521, United States
| | - Aspen Smith
- Department of Environmental
Sciences, University of California, Riverside, California 92521, United States
| | - Daniel Schlenk
- Department of Environmental
Sciences, University of California, Riverside, California 92521, United States
| | - Jay Gan
- Department of Environmental
Sciences, University of California, Riverside, California 92521, United States
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Yamamura Y, Yoshinari K, Yamazoe Y. Construction of a fused grid-based CYP2C19-Template system and the application. Drug Metab Pharmacokinet 2023; 48:100481. [PMID: 36813636 DOI: 10.1016/j.dmpk.2022.100481] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Revised: 10/05/2022] [Accepted: 10/22/2022] [Indexed: 11/11/2022]
Abstract
A ligand-accessible space in the CYP2C19 active site was reconstituted as a fused grid-based Template with the use of structural data of the ligands. An evaluation system of CYP2C19-mediated metabolism has been developed on Template with the introduction of the idea of Trigger-residue initiated ligand-movement and fastening. Reciprocal comparison of the data of simulation on Template with experimental results suggested a unified way of the interaction of CYP2C19 and its ligands through the simultaneous plural-contact with Rear-wall of Template. CYP2C19 was expected to have a room for ligands between vertically standing parallel walls termed Facial-wall and Rear-wall, which were separated by a distance corresponding to 1.5-Ring (grid) diameter size. The ligand sittings were stabilized through contacts with Facial-wall and the left-side borders of Template including specific Position 29 or Left-end after Trigger-residue initiated ligand-movement. Trigger-residue movement is suggested to force ligands to stay firmly in the active site and then to initiate CYP2C19 reactions. Simulation experiments for over 450 reactions of CYP2C19 ligands supported the system established.
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Affiliation(s)
- Yoshiya Yamamura
- Laboratory of Molecular Toxicology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan; Non-Clinical Regulatory Science, Applied Research & Operations, Astellas Pharma Inc., 21, Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan
| | - Kouichi Yoshinari
- Laboratory of Molecular Toxicology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Yasushi Yamazoe
- Division of Drug Metabolism and Molecular Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aramaki-Aoba, Aoba-ku, Sendai, 980-8578, Japan; Division of Risk Assessment, National Institute of Health Sciences, Tonomachi 3-25-26, Kawasaki-ku, Kawasaki, 210-9501, Japan.
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3
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Xiong Y, Shi Q, Sy ND, Dennis NM, Schlenk D, Gan J. Influence of methylation and demethylation on plant uptake of emerging contaminants. ENVIRONMENT INTERNATIONAL 2022; 170:107612. [PMID: 36347118 PMCID: PMC9988749 DOI: 10.1016/j.envint.2022.107612] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 10/29/2022] [Accepted: 10/31/2022] [Indexed: 06/16/2023]
Abstract
Contaminants of emerging concern (CECs) as well as their transformation products (TPs) are often found in treated wastewater and biosolids, raising concerns about their environmental risks. Small changes in chemical structure, such as the addition or loss of a methyl group, as the result of methylation or demethylation reaction, may significantly alter a chemical's physicochemical properties. In this study, we evaluated the difference in accumulation and translocation between four CECs and their respective methylated or demethylated derivatives in plant models. Suspended Arabidopsis thaliana cell culture and wheat seedlings were cultivated in nutrient solutions containing individual compounds at 1 mg/L. The methylated counterparts were generally more hydrophobic and showed comparative or greater accumulation in both plant models. For example, after 1 h incubation, methylparaben was found in A. thaliana cells at levels two orders of magnitude greater than demethylated methylparaben. In contrast, the demethylated counterparts, especially those with the addition of a hydroxyl group after demethylation, showed decreased plant uptake and limited translocation. For example, acetaminophen and demethylated naproxen were not detected in the shoots of wheat seedlings after hydroponic exposure. Results from this study suggest that common transformations such as methylation and demethylation may affect the environmental fate of CECs, and should be considered to obtain a more comprehensive understanding of risks of CECs in the environment.
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Affiliation(s)
- Yaxin Xiong
- Department of Environmental Sciences, University of California, Riverside, CA 92521, USA
| | - Qingyang Shi
- Department of Environmental Sciences, University of California, Riverside, CA 92521, USA
| | - Nathan D Sy
- Department of Environmental Sciences, University of California, Riverside, CA 92521, USA
| | - Nicole M Dennis
- Department of Environmental Sciences, University of California, Riverside, CA 92521, USA
| | - Daniel Schlenk
- Department of Environmental Sciences, University of California, Riverside, CA 92521, USA
| | - Jay Gan
- Department of Environmental Sciences, University of California, Riverside, CA 92521, USA.
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Sandson N. Important Drug-Drug Interactions for the Addiction Psychiatrist. Psychiatr Clin North Am 2022; 45:431-450. [PMID: 36055731 DOI: 10.1016/j.psc.2022.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The misuse of illicit substances, prescribed medications, and alcohol poses obvious health risks to afflicted individuals. When addressing these health risks, the overarching concerns generally relate to the direct effects that various substances can have on the functioning of multiple organ systems: cardiac, pulmonary, central nervous system, and others. What is not always evident, but potentially equally or even more dire, are the risks arising from drug-drug interactions involving illicit drugs and alcohol, whether with each other, or with prescribed medications. This review provides some basics that enable the reader to fruitfully approach the broad topic of drug-drug interactions.
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Affiliation(s)
- Neil Sandson
- Department of Psychiatry, University of Maryland, 126 East Aylesbury Road, Timonium, MD, USA; VA Maryland Health Care System, 10 North Greene St, Baltimore, MD 21201, USA.
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Pal R, Singh K, Khan SA, Chawla P, Kumar B, Akhtar MJ. Reactive metabolites of the anticonvulsant drugs and approaches to minimize the adverse drug reaction. Eur J Med Chem 2021; 226:113890. [PMID: 34628237 DOI: 10.1016/j.ejmech.2021.113890] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 09/01/2021] [Accepted: 09/29/2021] [Indexed: 12/22/2022]
Abstract
Several generations of antiepileptic drugs (AEDs) are available in the market for the treatment of seizures, but these are amalgamated with acute to chronic side effects. The most common side effects of AEDs are dose-related, but some are idiosyncratic adverse drug reactions (ADRs) that transpire due to the formation of reactive metabolite (RM) after the bioactivation process. Because of the adverse reactions patients usually discontinue the medication in between the treatment. The AEDs such as valproic acid, lamotrigine, phenytoin etc., can be categorized under such types because they form the RM which may prevail with life-threatening adverse effects or immune-mediated reactions. Hepatotoxicity, teratogenicity, cutaneous hypersensitivity, dizziness, addiction, serum sickness reaction, renal calculi, metabolic acidosis are associated with the metabolites of drugs such as arene oxide, N-desmethyldiazepam, 2-(1-hydroxyethyl)-2-methylsuccinimide, 2-(sulphamoy1acetyl)-phenol, E-2-en-VPA and 4-en-VPA and carbamazepine-10,11-epoxide, etc. The major toxicities are associated with the moieties that are either capable of forming RM or the functional groups may itself be too reactive prior to the metabolism. These functional groups or fragment structures are typically known as structural alerts or toxicophores. Therefore, minimizing the bioactivation potential of lead structures in the early phases of drug discovery by a modification to low-risk drug molecules is a priority for the pharmaceutical companies. Additionally, excellent potency and pharmacokinetic (PK) behaviour help in ensuring that appropriate (low dose) candidate drugs progress into the development phase. The current review discusses about RMs in the anticonvulsant drugs along with their mechanism vis-a-vis research efforts that have been taken to minimize the toxic effects of AEDs therapy.
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Affiliation(s)
- Rohit Pal
- Department of Pharmaceutical Chemistry, ISF College of Pharmacy, Ghal Kalan, Ferozpur, G.T. Road, Moga, 142001, Punjab, India
| | - Karanvir Singh
- Department of Pharmaceutical Chemistry, ISF College of Pharmacy, Ghal Kalan, Ferozpur, G.T. Road, Moga, 142001, Punjab, India
| | - Shah Alam Khan
- Department of Pharmaceutical Chemistry, College of Pharmacy, National University of Science and Technology, PO 620, PC 130, Azaiba, Bousher, Muscat, Oman
| | - Pooja Chawla
- Department of Pharmaceutical Chemistry, ISF College of Pharmacy, Ghal Kalan, Ferozpur, G.T. Road, Moga, 142001, Punjab, India
| | - Bhupinder Kumar
- Department of Pharmaceutical Chemistry, ISF College of Pharmacy, Ghal Kalan, Ferozpur, G.T. Road, Moga, 142001, Punjab, India.
| | - Md Jawaid Akhtar
- Department of Pharmaceutical Chemistry, ISF College of Pharmacy, Ghal Kalan, Ferozpur, G.T. Road, Moga, 142001, Punjab, India; Department of Pharmaceutical Chemistry, College of Pharmacy, National University of Science and Technology, PO 620, PC 130, Azaiba, Bousher, Muscat, Oman.
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A Physiologically Based Pharmacokinetic Model for Predicting Diazepam Pharmacokinetics after Intravenous, Oral, Intranasal, and Rectal Applications. Pharmaceutics 2021; 13:pharmaceutics13091480. [PMID: 34575556 PMCID: PMC8465253 DOI: 10.3390/pharmaceutics13091480] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 09/07/2021] [Accepted: 09/13/2021] [Indexed: 12/17/2022] Open
Abstract
Diazepam is one of the most prescribed anxiolytic and anticonvulsant that is administered through intravenous (IV), oral, intramuscular, intranasal, and rectal routes. To facilitate the clinical use of diazepam, there is a need to develop formulations that are convenient to administer in ambulatory settings. The present study aimed to develop and evaluate a physiologically based pharmacokinetic (PBPK) model for diazepam that is capable of predicting its pharmacokinetics (PK) after IV, oral, intranasal, and rectal applications using a whole-body population-based PBPK simulator, Simcyp®. The model evaluation was carried out using visual predictive checks, observed/predicted ratios (Robs/pred), and the average fold error (AFE) of PK parameters. The Diazepam PBPK model successfully predicted diazepam PK in an adult population after doses were administered through IV, oral, intranasal, and rectal routes, as the Robs/pred of all PK parameters were within a two-fold error range. The developed model can be used for the development and optimization of novel diazepam dosage forms, and it can be extended to simulate drug response in situations where no clinical data are available (healthy and disease).
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Skoda J, Dusek J, Drastik M, Stefela A, Dohnalova K, Chalupsky K, Smutny T, Micuda S, Gerbal-Chaloin S, Pavek P. Diazepam Promotes Translocation of Human Constitutive Androstane Receptor (CAR) via Direct Interaction with the Ligand-Binding Domain. Cells 2020; 9:cells9122532. [PMID: 33255185 PMCID: PMC7761063 DOI: 10.3390/cells9122532] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/07/2020] [Accepted: 11/20/2020] [Indexed: 11/17/2022] Open
Abstract
The constitutive androstane receptor (CAR) is the essential regulator of genes involved both in xenobiotic and endobiotic metabolism. Diazepam has been shown as a potent stimulator of CAR nuclear translocation and is assumed as an indirect CAR activator not interacting with the CAR cavity. In this study, we sought to determine if diazepam is a ligand directly interacting with the CAR ligand binding domain (LBD) and if it regulates its target genes in a therapeutically relevant concentration. We used different CAR constructs in translocation and luciferase reporter assays, recombinant CAR-LBD in a TR-FRET assay, and target genes induction studied in primary human hepatocytes (PHHs), HepaRG cells, and in CAR humanized mice. We also used in silico docking and CAR-LBD mutants to characterize the interaction of diazepam and its metabolites with the CAR cavity. Diazepam and its metabolites such as nordazepam, temazepam, and oxazepam are activators of CAR+Ala in translocation and two-hybrid assays and fit the CAR cavity in docking experiments. In gene reporter assays with CAR3 and in the TR-FRET assay, only diazepam significantly interacts with CAR-LBD. Diazepam also promotes up-regulation of CYP2B6 in PHHs and in HepaRG cells. However, in humanized CAR mice, diazepam significantly induces neither CYP2B6 nor Cyp2b10 genes nor does it regulate critical genes involved in glucose and lipids metabolism and liver proliferation. Thus, we demonstrate that diazepam interacts with human CAR-LBD as a weak ligand, but it does not significantly affect expression of tested CAR target genes in CAR humanized mice.
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Affiliation(s)
- Josef Skoda
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, 500 05 Hradec Kralove, Czech Republic; (J.S.); (J.D.); (A.S.); (T.S.)
| | - Jan Dusek
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, 500 05 Hradec Kralove, Czech Republic; (J.S.); (J.D.); (A.S.); (T.S.)
| | - Martin Drastik
- Department of Physical Chemistry and Biophysics, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, 500 05 Hradec Kralove, Czech Republic;
| | - Alzbeta Stefela
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, 500 05 Hradec Kralove, Czech Republic; (J.S.); (J.D.); (A.S.); (T.S.)
| | - Klara Dohnalova
- 1 Medical Faculty, Charles University, Katerinská 32, 121 08 Prague, Czech Republic;
- Czech Centre for Phenogenomics, Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic;
| | - Karel Chalupsky
- Czech Centre for Phenogenomics, Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic;
| | - Tomas Smutny
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, 500 05 Hradec Kralove, Czech Republic; (J.S.); (J.D.); (A.S.); (T.S.)
| | - Stanislav Micuda
- Department of Pharmacology, Medical Faculty in Hradec Kralove, Charles University, Simkova 870, 500 03 Hradec Kralove, Czech Republic;
| | | | - Petr Pavek
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, 500 05 Hradec Kralove, Czech Republic; (J.S.); (J.D.); (A.S.); (T.S.)
- Correspondence: ; Tel.: +420-495-067-334
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Tanna RS, Tian DD, Cech NB, Oberlies NH, Rettie AE, Thummel KE, Paine MF. Refined Prediction of Pharmacokinetic Kratom-Drug Interactions: Time-Dependent Inhibition Considerations. J Pharmacol Exp Ther 2020; 376:64-73. [PMID: 33093187 DOI: 10.1124/jpet.120.000270] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 10/08/2020] [Indexed: 02/06/2023] Open
Abstract
Preparations from the leaves of the kratom plant (Mitragyna speciosa) are consumed for their opioid-like effects. Several deaths have been associated with kratom used concomitantly with some drugs. Pharmacokinetic interactions are potential underlying mechanisms of these fatalities. Accumulating in vitro evidence has demonstrated select kratom alkaloids, including the abundant indole alkaloid mitragynine, as reversible inhibitors of several cytochromes P450 (CYPs). The objective of this work was to refine the mechanistic understanding of potential kratom-drug interactions by considering both reversible and time-dependent inhibition (TDI) of CYPs in the liver and intestine. Mitragynine was tested against CYP2C9 (diclofenac 4'-hydroxylation), CYP2D6 (dextromethorphan O-demethylation), and CYP3A (midazolam 1'-hydroxylation) activities in human liver microsomes (HLMs) and CYP3A activity in human intestinal microsomes (HIMs). Comparing the absence to presence of NADPH during preincubation of mitragynine with HLMs or HIMs, an ∼7-fold leftward shift in IC50 (∼20 to 3 μM) toward CYP3A resulted, prompting determination of TDI parameters (HLMs: K I , 4.1 ± 0.9 μM; k inact , 0.068 ± 0.01 min-1; HIMs: K I , 4.2 ± 2.5 μM; k inact , 0.079 ± 0.02 min-1). Mitragynine caused no leftward shift in IC50 toward CYP2C9 (∼40 μM) and CYP2D6 (∼1 μM) but was a strong competitive inhibitor of CYP2D6 (K i , 1.17 ± 0.07 μM). Using a recommended mechanistic static model, mitragynine (2-g kratom dose) was predicted to increase dextromethorphan and midazolam area under the plasma concentration-time curve by 1.06- and 5.69-fold, respectively. The predicted midazolam area under the plasma concentration-time curve ratio exceeded the recommended cutoff (1.25), which would have been missed if TDI was not considered. SIGNIFICANCE STATEMENT: Kratom, a botanical natural product increasingly consumed for its opioid-like effects, may precipitate potentially serious pharmacokinetic interactions with drugs. The abundant kratom indole alkaloid mitragynine was shown to be a time-dependent inhibitor of hepatic and intestinal cytochrome P450 3A activity. A mechanistic static model predicted mitragynine to increase systemic exposure to the probe drug substrate midazolam by 5.7-fold, necessitating further evaluation via dynamic models and clinical assessment to advance the understanding of consumer safety associated with kratom use.
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Affiliation(s)
- Rakshit S Tanna
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (R.S.T., D.-D.T., M.F.P.); Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, North Carolina (N.B.C., N.H.O.); Departments of Medicinal Chemistry (A.E.R.) and Pharmaceutics (K.E.T.), School of Pharmacy, University of Washington, Seattle, Washington; and Center of Excellence for Natural Product Drug Interaction Research, Spokane, Washington (N.B.C., N.H.O., A.E.R., K.E.T., M.F.P.)
| | - Dan-Dan Tian
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (R.S.T., D.-D.T., M.F.P.); Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, North Carolina (N.B.C., N.H.O.); Departments of Medicinal Chemistry (A.E.R.) and Pharmaceutics (K.E.T.), School of Pharmacy, University of Washington, Seattle, Washington; and Center of Excellence for Natural Product Drug Interaction Research, Spokane, Washington (N.B.C., N.H.O., A.E.R., K.E.T., M.F.P.)
| | - Nadja B Cech
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (R.S.T., D.-D.T., M.F.P.); Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, North Carolina (N.B.C., N.H.O.); Departments of Medicinal Chemistry (A.E.R.) and Pharmaceutics (K.E.T.), School of Pharmacy, University of Washington, Seattle, Washington; and Center of Excellence for Natural Product Drug Interaction Research, Spokane, Washington (N.B.C., N.H.O., A.E.R., K.E.T., M.F.P.)
| | - Nicholas H Oberlies
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (R.S.T., D.-D.T., M.F.P.); Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, North Carolina (N.B.C., N.H.O.); Departments of Medicinal Chemistry (A.E.R.) and Pharmaceutics (K.E.T.), School of Pharmacy, University of Washington, Seattle, Washington; and Center of Excellence for Natural Product Drug Interaction Research, Spokane, Washington (N.B.C., N.H.O., A.E.R., K.E.T., M.F.P.)
| | - Allan E Rettie
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (R.S.T., D.-D.T., M.F.P.); Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, North Carolina (N.B.C., N.H.O.); Departments of Medicinal Chemistry (A.E.R.) and Pharmaceutics (K.E.T.), School of Pharmacy, University of Washington, Seattle, Washington; and Center of Excellence for Natural Product Drug Interaction Research, Spokane, Washington (N.B.C., N.H.O., A.E.R., K.E.T., M.F.P.)
| | - Kenneth E Thummel
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (R.S.T., D.-D.T., M.F.P.); Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, North Carolina (N.B.C., N.H.O.); Departments of Medicinal Chemistry (A.E.R.) and Pharmaceutics (K.E.T.), School of Pharmacy, University of Washington, Seattle, Washington; and Center of Excellence for Natural Product Drug Interaction Research, Spokane, Washington (N.B.C., N.H.O., A.E.R., K.E.T., M.F.P.)
| | - Mary F Paine
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (R.S.T., D.-D.T., M.F.P.); Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, North Carolina (N.B.C., N.H.O.); Departments of Medicinal Chemistry (A.E.R.) and Pharmaceutics (K.E.T.), School of Pharmacy, University of Washington, Seattle, Washington; and Center of Excellence for Natural Product Drug Interaction Research, Spokane, Washington (N.B.C., N.H.O., A.E.R., K.E.T., M.F.P.)
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Rahman H, Haque SM, Siddiqui MR. A Comprehensive Review on Importance and Quantitation of Atypical Antipsychotic Drugs and their Active Metabolites in Commercial Dosage Forms. CURR PHARM ANAL 2020. [DOI: 10.2174/1573412915666190328214323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Background:
Schizophrenia is a severe mental illness that affects more than twenty-one
million people throughout the world. Schizophrenia also causes early death. Schizophrenia and other
related psychotic ailments are controlled by the prescription of antipsychotic drugs, which act by blocking
certain chemical receptors in the brain and thus relieves the symptoms of psychotic disorder. These
drugs are present in the different dosage forms in the market and provided in a certain amount as per the
need of the patients.
Objective:
Since such medications treat mental disorders, it is very important to have a perfect and accurate
dose so that the risk factor is not affected by a higher or lower dose, which is not sufficient for
the treatment. For accurate assay of these kinds of drugs, different analytical methods were developed
ranging from older spectrophotometric techniques to latest hyphenated methods.
Results:
The current review highlights the role of different analytical techniques that were employed in
the determination and identification of antipsychotic drugs and their metabolites. Techniques such as
spectrophotometry, fluorimetry, liquid chromatography, liquid chromatography-mass spectrometry, gas
chromatography, and gas chromatography-mass spectrometry employed in the method development of
such antipsychotic drugs were reported in the review. Different metabolites, identified using the hyphenated
techniques, were also mentioned in the review. The synthesis pathways of few of the metabolites
were mentioned.
Conclusion:
The review summarizes the analyses of different antipsychotic drugs and their metabolites.
A brief introduction of illnesses and their symptoms and possible medications were highlighted. Synthesis
pathways of the associated metabolites were also mentioned.
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Affiliation(s)
- Habibur Rahman
- Department of General Studies, Jubail Industrial College, P.O. Box No. 10099, Zip Code–31961, Jubail, Saudi Arabia
| | - S.K. Manirul Haque
- Department of Chemical & Process Engineering Technology, Jubail Industrial College, P.O. Box No 10099, Zip Code- 31961, Jubail, Saudi Arabia
| | - Masoom Raza Siddiqui
- Chemistry Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
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Salerno S, Tasselli F, Drioli E, De Bartolo L. Poly(ε-Caprolactone) Hollow Fiber Membranes for the Biofabrication of a Vascularized Human Liver Tissue. MEMBRANES 2020; 10:E112. [PMID: 32471264 PMCID: PMC7344547 DOI: 10.3390/membranes10060112] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 05/23/2020] [Accepted: 05/26/2020] [Indexed: 01/01/2023]
Abstract
The creation of a liver tissue that recapitulates the micro-architecture and functional complexity of a human organ is still one of the main challenges of liver tissue engineering. Here we report on the development of a 3D vascularized hepatic tissue based on biodegradable hollow fiber (HF) membranes of poly(ε-caprolactone) (PCL) that compartmentalize human hepatocytes on the external surface and between the fibers, and endothelial cells into the fiber lumen. To this purpose, PCL HF membranes were prepared by a dry-jet wet phase inversion spinning technique tailoring the operational parameters in order to obtain fibers with suitable properties. After characterization, the fibers were applied to generate a human vascularized hepatic unit by loading endothelial cells in their inner surface and hepatocytes on the external surface. The unit was connected to a perfusion system, and the morpho-functional behavior was evaluated. The results demonstrated the large integration of endothelial cells with the internal surface of individual PCL fibers forming vascular-like structures, and hepatocytes covered completely the external surface and the space between fibers. The perfused 3D hepatic unit retained its functional activity at high levels up to 18 days. This bottom-up tissue engineering approach represents a rational strategy to create relatively 3D vascularized tissues and organs.
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Affiliation(s)
- Simona Salerno
- CNR-ITM, Institute on Membrane Technology, National Research Council of Italy, via P. Bucci, cubo 17/C, I-87036 Rende, Italy; (S.S.); (F.T.); (E.D.)
| | - Franco Tasselli
- CNR-ITM, Institute on Membrane Technology, National Research Council of Italy, via P. Bucci, cubo 17/C, I-87036 Rende, Italy; (S.S.); (F.T.); (E.D.)
| | - Enrico Drioli
- CNR-ITM, Institute on Membrane Technology, National Research Council of Italy, via P. Bucci, cubo 17/C, I-87036 Rende, Italy; (S.S.); (F.T.); (E.D.)
- Department of Energy, Engineering, Hanyang University, Seoul 04763, Korea
| | - Loredana De Bartolo
- CNR-ITM, Institute on Membrane Technology, National Research Council of Italy, via P. Bucci, cubo 17/C, I-87036 Rende, Italy; (S.S.); (F.T.); (E.D.)
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Dallmann A, Ince I, Coboeken K, Eissing T, Hempel G. A Physiologically Based Pharmacokinetic Model for Pregnant Women to Predict the Pharmacokinetics of Drugs Metabolized Via Several Enzymatic Pathways. Clin Pharmacokinet 2019; 57:749-768. [PMID: 28924743 DOI: 10.1007/s40262-017-0594-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
BACKGROUND Physiologically based pharmacokinetic modeling is considered a valuable tool for predicting pharmacokinetic changes in pregnancy to subsequently guide in-vivo pharmacokinetic trials in pregnant women. The objective of this study was to extend and verify a previously developed physiologically based pharmacokinetic model for pregnant women for the prediction of pharmacokinetics of drugs metabolized via several cytochrome P450 enzymes. METHODS Quantitative information on gestation-specific changes in enzyme activity available in the literature was incorporated in a pregnancy physiologically based pharmacokinetic model and the pharmacokinetics of eight drugs metabolized via one or multiple cytochrome P450 enzymes was predicted. The tested drugs were caffeine, midazolam, nifedipine, metoprolol, ondansetron, granisetron, diazepam, and metronidazole. Pharmacokinetic predictions were evaluated by comparison with in-vivo pharmacokinetic data obtained from the literature. RESULTS The pregnancy physiologically based pharmacokinetic model successfully predicted the pharmacokinetics of all tested drugs. The observed pregnancy-induced pharmacokinetic changes were qualitatively and quantitatively reasonably well predicted for all drugs. Ninety-seven percent of the mean plasma concentrations predicted in pregnant women fell within a twofold error range and 63% within a 1.25-fold error range. For all drugs, the predicted area under the concentration-time curve was within a 1.25-fold error range. CONCLUSION The presented pregnancy physiologically based pharmacokinetic model can quantitatively predict the pharmacokinetics of drugs that are metabolized via one or multiple cytochrome P450 enzymes by integrating prior knowledge of the pregnancy-related effect on these enzymes. This pregnancy physiologically based pharmacokinetic model may thus be used to identify potential exposure changes in pregnant women a priori and to eventually support informed decision making when clinical trials are designed in this special population.
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Affiliation(s)
- André Dallmann
- Department of Pharmaceutical and Medical Chemistry, Clinical Pharmacy, Westfälische Wilhelms-University Münster, 48149, Münster, Germany.
| | - Ibrahim Ince
- Clinical Pharmacometrics, Bayer AG, 51368, Leverkusen, Germany
| | - Katrin Coboeken
- Clinical Pharmacometrics, Bayer AG, 51368, Leverkusen, Germany
| | - Thomas Eissing
- Clinical Pharmacometrics, Bayer AG, 51368, Leverkusen, Germany
| | - Georg Hempel
- Department of Pharmaceutical and Medical Chemistry, Clinical Pharmacy, Westfälische Wilhelms-University Münster, 48149, Münster, Germany
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Yamazoe Y, Goto T, Tohkin M. Reconstitution of CYP3A4 active site through assembly of ligand interactions as a grid-template: Solving the modes of the metabolism and inhibition. Drug Metab Pharmacokinet 2019; 34:113-125. [DOI: 10.1016/j.dmpk.2018.10.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 09/30/2018] [Accepted: 10/10/2018] [Indexed: 01/16/2023]
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Yilmaz Y, Williams G, Walles M, Manevski N, Krähenbühl S, Camenisch G. Comparison of Rat and Human Pulmonary Metabolism Using Precision-cut Lung Slices (PCLS). Drug Metab Lett 2019; 13:53-63. [PMID: 30345935 DOI: 10.2174/1872312812666181022114622] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 09/28/2018] [Accepted: 10/08/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Although the liver is the primary organ of drug metabolism, the lungs also contain drug-metabolizing enzymes and may, therefore, contribute to the elimination of drugs. In this investigation, the Precision-cut Lung Slice (PCLS) technique was standardized with the aims of characterizing and comparing rat and human pulmonary drug metabolizing activity. METHOD Due to the limited availability of human lung tissue, standardization of the PCLS method was performed with rat lung tissue. Pulmonary enzymatic activity was found to vary significantly with rat age and rat strain. The Dynamic Organ Culture (DOC) system was superior to well-plates for tissue incubations, while oxygen supply appeared to have a limited impact within the 4h incubation period used here. RESULTS The metabolism of a range of phase I and phase II probe substrates was assessed in rat and human lung preparations. Cytochrome P450 (CYP) activity was relatively low in both species, whereas phase II activity appeared to be more significant. CONCLUSION PCLS is a promising tool for the investigation of pulmonary drug metabolism. The data indicates that pulmonary CYP activity is relatively low and that there are significant differences in enzyme activity between rat and human lung.
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Affiliation(s)
- Yildiz Yilmaz
- Pharmacokinetic Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Gareth Williams
- Pharmacokinetic Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Markus Walles
- Pharmacokinetic Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Nenad Manevski
- Pharmacokinetic Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Stephan Krähenbühl
- Clinical Pharmacology and Toxicology, University Hospital, Basel, Switzerland
| | - Gian Camenisch
- Pharmacokinetic Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
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Hedrich WD, Hassan HE, Wang H. Insights into CYP2B6-mediated drug-drug interactions. Acta Pharm Sin B 2016; 6:413-425. [PMID: 27709010 PMCID: PMC5045548 DOI: 10.1016/j.apsb.2016.07.016] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 05/18/2016] [Accepted: 05/27/2016] [Indexed: 01/11/2023] Open
Abstract
Mounting evidence demonstrates that CYP2B6 plays a much larger role in human drug metabolism than was previously believed. The discovery of multiple important substrates of CYP2B6 as well as polymorphic differences has sparked increasing interest in the genetic and xenobiotic factors contributing to the expression and function of the enzyme. The expression of CYP2B6 is regulated primarily by the xenobiotic receptors constitutive androstane receptor (CAR) and pregnane X receptor (PXR) in the liver. In addition to CYP2B6, these receptors also mediate the inductive expression of CYP3A4, and a number of important phase II enzymes and drug transporters. CYP2B6 has been demonstrated to play a role in the metabolism of 2%–10% of clinically used drugs including widely used antineoplastic agents cyclophosphamide and ifosfamide, anesthetics propofol and ketamine, synthetic opioids pethidine and methadone, and the antiretrovirals nevirapine and efavirenz, among others. Significant inter-individual variability in the expression and function of the human CYP2B6 gene exists and can result in altered clinical outcomes in patients receiving treatment with CYP2B6-substrate drugs. These variances arise from a number of sources including genetic polymorphism, and xenobiotic intervention. In this review, we will provide an overview of the key players in CYP2B6 expression and function and highlight recent advances made in assessing clinical ramifications of important CYP2B6-mediated drug–drug interactions.
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Key Words
- 4-OH-CPA, 4-hydroxycyclophosphamide
- C/EBP, CCAAT/enhancer-binding protein
- CAR
- CAR, constitutive androstane receptor
- CHOP, cyclophosphamide–doxorubicin–vincristine–prednisone
- CITCO, (6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime)
- COUP-TF, chicken ovalbumin upstream promoter-transcription factor
- CPA, cyclophosphamide
- CYP, cytochrome P450
- CYP2B6
- Cyclophosphamide
- DDI, drug–drug interaction
- DEX, dexamethasone
- Drug–drug interaction
- E2, estradiol
- EFV, efavirenz
- ERE, estrogen responsive element
- Efavirenz
- GR, glucocorticoid receptor
- GRE, glucocorticoid responsive element
- HAART, highly active antiretroviral therapy
- HNF, hepatocyte nuclear factor
- IFA, Ifosfamide
- MAOI, monoamine oxidase inhibitor
- NNRTI, non-nucleotide reverse-transcriptase inhibitor
- NR1/2, nuclear receptor binding site 1/2
- NVP, nevirapine
- PB, phenobarbital
- PBREM, phenobarbital-responsive enhancer module
- PCN, pregnenolone 16 alpha-carbonitrile
- PXR
- PXR, pregnane X receptor
- Polymorphism
- RIF, rifampin
- SNP, single nucleotide polymorphism
- TCPOBOP, 1,4-bis[3,5-dichloropyridyloxy]benzene
- UGT, UDP-glucuronosyl transferase
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Affiliation(s)
| | | | - Hongbing Wang
- Corresponding author at: Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 Penn Street, Baltimore, MD 21201, USA. Tel.: +1 410 706 1280; fax: +1 410 706 5017.
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Jin T, Zhang X, Geng T, Shi X, Wang L, Yuan D, Kang L. Genotype‑phenotype analysis of CYP2C19 in the Tibetan population and its potential clinical implications in drug therapy. Mol Med Rep 2016; 13:2117-23. [PMID: 26781306 PMCID: PMC4768997 DOI: 10.3892/mmr.2016.4776] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Accepted: 12/18/2015] [Indexed: 12/12/2022] Open
Abstract
Cytochrome P450 2C19 (CYP2C19) is a highly polymorphic gene, it codes for a protein responsible for the metabolism of multiple clinically important therapeutic agents. However, there is currently no available data on the distribution of CYP2C19 mutant alleles in the Tibetan population. The aim of the present study was to identify different CYP2C19 mutant alleles and determine their frequencies, along with genotypic frequencies, in the Tibetan population. The whole CYP2C19 gene was amplified and sequenced in 96 unrelated, healthy Tibetans from the Tibet Autonomous Region of China, the promoter region, exons, introns and the 3'‑UTR were screened for genetic variants. Three novel genetic polymorphisms in CYP2C19 were detected among a total of 27 different mutations. The allele frequencies of CYP2C19*1A, *1B, *2A, *3A and *17 were 50, 28.13, 15.10, 5.21 and 1.56%, respectively. The most common genotype combinations were CYP2C19*1A/*1B (56.25%) and *1A/*2A (30.21%). One novel non‑synonymous mutation (Asn to Lys) in CYP2C19 was identified, and this mutation was predicted to be intolerant and benign by SIFT and PolyPhen‑2, respectively. The observations of the present study may have important clinical implications for the use of medications metabolized by CYP2C19 among Tibetans.
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Affiliation(s)
- Tianbo Jin
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi 712082, P.R. China
| | - Xiyang Zhang
- School of Life Sciences, Northwest University, Xi'an, Shaanxi 710069, P.R. China
| | - Tingting Geng
- Department of Endocrinology, The First Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, Shaanxi 710061, P.R. China
| | - Xugang Shi
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi 712082, P.R. China
| | - Li Wang
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi 712082, P.R. China
| | - Dongya Yuan
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi 712082, P.R. China
| | - Longli Kang
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi 712082, P.R. China
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Holovenko MI, Larionov VB. [Kinetics of hydrolysis of 1,4-benzodiazepine derivative by carboxylesterases in mice organism]. UKRAINIAN BIOCHEMICAL JOURNAL 2014; 86:150-7. [PMID: 25509194 DOI: 10.15407/ubj86.04.150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Chemical modification of the physiologically active substances and creation of prodrugs is one of the ways for pharmacotherapy optimization. The aim of the work was determination of the kinetic parameters ofnonspecific esterases that catalyze hydrolysis of new hypnotic drug Levana (1,4-benzodiazepine derivative). The experiments were carried out using the 14C-labelled Levana and its active metabolite - 3-hydrixyphenazepam. In vitro it was shown that Levana undergoes spontaneous hydrolysis even in buffer solution (pH 7.4), though in plasma and homogenates of brain and liver this process is more intensive (conventional Vmax was 6.9 ± 0.5, 19 ± 4 and 12 ± 1 mM/(h·mg of protein, correspondingly). The samples mentioned differ by activity of tissue esterases being most active in the liver (conventional K 0.45 ± 0.04 mM for the liver and 47 ± 11 mM for the brain). In plasma carboxylesterase activity (for Levana) is the lowest (conventional K 129 ± 10 mM). In vivo it was shown that Levana more easily permeates brain-blood barrier (compared to 3-hydroxyphenazepam), that leads to higher concentrations (after hydrolysis) of its metabolite in brain tissue. Also it is quantitatively estimated as the increase of concentration (brain/blood) ratio ~1.4 times.
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Calcaterra NE, Barrow JC. Classics in chemical neuroscience: diazepam (valium). ACS Chem Neurosci 2014; 5:253-60. [PMID: 24552479 DOI: 10.1021/cn5000056] [Citation(s) in RCA: 152] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Diazepam (Valium) is among the most successful drugs from the onset of the psychopharmacological revolution that began during the 1950s. Efficacious in treating a wide-spectrum of CNS disorders, including anxiety and epilepsy, it set the standard for pharmacotherapy in terms of potency, onset of action, and safety. In this Review, the legacy of diazepam to chemical neuroscience will be considered along with its synthesis, pharmacology, drug metabolism, adverse events and dependence, clinical use, and regulatory issues.
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Affiliation(s)
- Nicholas E. Calcaterra
- Department
of Pharmacology, Johns Hopkins University, Baltimore, Maryland 21205, United States
| | - James C. Barrow
- Department
of Pharmacology, Johns Hopkins University, Baltimore, Maryland 21205, United States
- Lieber Institute for Brain Development, Baltimore, Maryland 21205, United States
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Schiffman SS, Rother KI. Sucralose, a synthetic organochlorine sweetener: overview of biological issues. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2013; 16:399-451. [PMID: 24219506 PMCID: PMC3856475 DOI: 10.1080/10937404.2013.842523] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Sucralose is a synthetic organochlorine sweetener (OC) that is a common ingredient in the world's food supply. Sucralose interacts with chemosensors in the alimentary tract that play a role in sweet taste sensation and hormone secretion. In rats, sucralose ingestion was shown to increase the expression of the efflux transporter P-glycoprotein (P-gp) and two cytochrome P-450 (CYP) isozymes in the intestine. P-gp and CYP are key components of the presystemic detoxification system involved in first-pass drug metabolism. The effect of sucralose on first-pass drug metabolism in humans, however, has not yet been determined. In rats, sucralose alters the microbial composition in the gastrointestinal tract (GIT), with relatively greater reduction in beneficial bacteria. Although early studies asserted that sucralose passes through the GIT unchanged, subsequent analysis suggested that some of the ingested sweetener is metabolized in the GIT, as indicated by multiple peaks found in thin-layer radiochromatographic profiles of methanolic fecal extracts after oral sucralose administration. The identity and safety profile of these putative sucralose metabolites are not known at this time. Sucralose and one of its hydrolysis products were found to be mutagenic at elevated concentrations in several testing methods. Cooking with sucralose at high temperatures was reported to generate chloropropanols, a potentially toxic class of compounds. Both human and rodent studies demonstrated that sucralose may alter glucose, insulin, and glucagon-like peptide 1 (GLP-1) levels. Taken together, these findings indicate that sucralose is not a biologically inert compound.
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Affiliation(s)
- Susan S. Schiffman
- Department of Electrical and Computer Engineering, College of Engineering, North Carolina State University, Raleigh, North Carolina, USA
- Address correspondence to Susan S. Schiffman, PhD, Department of Electrical and Computer Engineering, College of Engineering, North Carolina State University, Raleigh, NC 27695-7911, USA. E-mail:
| | - Kristina I. Rother
- Section on Pediatric Diabetes & Metabolism, Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, Bethesda, Maryland, USA
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Saeed LH, Mayet AY. Genotype-phenotype analysis of CYP2C19 in healthy saudi individuals and its potential clinical implication in drug therapy. Int J Med Sci 2013; 10:1497-502. [PMID: 24046523 PMCID: PMC3775106 DOI: 10.7150/ijms.6795] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 07/29/2013] [Indexed: 01/01/2023] Open
Abstract
UNLABELLED CYP2C19 is a cytochrome P450 enzyme, which is involved in the metabolism of some clinically important medications and is encoded by a highly polymorphic gene. There is no available data on the distribution of the CYP2C19 *4 and *17 mutant alleles in the Saudi Arabian population. The aim of the study was to determine different CYP2C19 mutant allele (*2, *4 and *17) frequencies in healthy Saudi subjects and to determine genotype frequencies for these mutations. The CYP2C19 genotypes were then classified into phenotypes. RESULT In 201 adults of Saudi ethnicity, the allele frequencies were CYP2C19*1 (62.9%), *17 (25.7%), *2 (11.2%) and *4 (0.2%). The most prevalent genotype combinations were CYP2C19 *1/*1 (40.3%) and *1/*17 (30.4%). The distribution of CYP2C19 phenotypes was divided into extensive metabolizers (EM) 77.6%, intermediate metabolizers (IM) 14.9%, ultra-rapid metabolizers (UM) 7% and poor metabolizers (PM) 0.4%. This finding has important clinical implications for the use of CYP2C19 metabolized medications in the Saudi population and further studies are needed.
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Affiliation(s)
- Leena H Saeed
- 1. King Fahad Medical City, P.O. Box 59046, Riyadh 11525, Kingdom of Saudi Arabia
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Salerno S, Campana C, Morelli S, Drioli E, De Bartolo L. Human hepatocytes and endothelial cells in organotypic membrane systems. Biomaterials 2011; 32:8848-59. [PMID: 21871658 DOI: 10.1016/j.biomaterials.2011.08.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 08/04/2011] [Indexed: 10/17/2022]
Abstract
The realization of organotypic liver model that exhibits stable phenotype is a major challenge in the field of liver tissue engineering. In this study we developed liver organotypic co-culture systems by using synthetic and biodegradable membranes with primary human hepatocytes and human umbilical vein endothelial cells (HUVEC). Synthetic membranes prepared by a polymeric blend constituted of modified polyetheretherketone (PEEK-WC) and polyurethane (PU) and biodegradable chitosan membranes were developed by phase inversion technique and used in homotypic and organotypic culture systems. The morphological and functional characteristics of cells in the organotypic co-culture membrane systems were evaluated in comparison with homotypic cultures and traditional systems. Hepatocytes in the organotypic co-culture systems exhibit compact polyhedral cells with round nuclei and well demarcated cell-cell borders like in vivo, as a result of heterotypic interaction with HUVECs. In addition HUVECs formed tube-like structures directly through the interactions with the membranes and hepatocytes and indirectly through the secretion of ECM proteins which secretion improved in the organotypic co-culture membrane systems. The heterotypic cell-cell contacts have beneficial effect on the hepatocyte albumin production, urea synthesis and drug biotransformation. The developed organotypic co-culture membrane systems elicit liver specific functions in vitro and could be applied for the realization of engineered liver tissues to be used in tissue engineering, drug metabolism studies and bioartificial liver devices.
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Affiliation(s)
- Simona Salerno
- Institute on Membrane Technology, National Research Council of Italy, ITM-CNR, c/o University of Calabria, Rende (CS), Italy
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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.
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Affiliation(s)
- Shu-Feng Zhou
- School of Health Sciences, RMIT University, Victoria 3083, Australia.
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Acikgöz A, Karim N, Giri S, Schmidt-Heck W, Bader A. Two compartment model of diazepam biotransformation in an organotypical culture of primary human hepatocytes. Toxicol Appl Pharmacol 2009; 234:179-91. [DOI: 10.1016/j.taap.2008.09.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Accepted: 09/25/2008] [Indexed: 10/21/2022]
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Wang H, Tompkins LM. CYP2B6: new insights into a historically overlooked cytochrome P450 isozyme. Curr Drug Metab 2008; 9:598-610. [PMID: 18781911 DOI: 10.2174/138920008785821710] [Citation(s) in RCA: 226] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Human CYP2B6 has been thought to account for a minor portion (<1%) of total hepatic cytochrome P450 (CYP) content and to have a minor function in human drug metabolism. Recent studies, however, indicate that the average relative contribution of CYP2B6 to total hepatic CYP content ranges from 2% to 10%. An increased interest in CYP2B6 research has been stimulated by the identification of an ever-increasing substrate list for this enzyme, polymorphic and ethnic variations in expression levels, and evidence for cross-regulation with CYP3A4, UGT1A1 and several hepatic drug transporters by the nuclear receptors pregnane X receptor and constitutive androstane receptor. Moreover, 20- to 250-fold interindividual variation in CYP2B6 expression has been demonstrated, presumably due to transcriptional regulation and polymorphisms. These individual differences may result in variable systemic exposure to drugs metabolized by CYP2B6, including the antineoplastics cyclophosphamide and ifosfamide, the antiretrovirals nevirapine and efavirenz, the anesthetics propofol and ketamine, the synthetic opioid methadone, and the anti-Parkinsonian selegiline. The potential clinical significance of CYP2B6 further enforces the need for a comprehensive review of this xenobiotic metabolizing enzyme. This communication summarizes recent advances in our understanding of this traditionally neglected enzyme and provides an overall picture of CYP2B6 with respect to expression, localization, substrate-specificity, inhibition, regulation, polymorphisms and clinical significance. Emphasis is given to nuclear receptor mediated transcriptional regulation, genetic polymorphisms, and their clinical significance.
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Affiliation(s)
- Hongbing Wang
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland at Baltimore, 20 Penn Street, Baltimore, MD 21201, USA.
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Mizuno K, Katoh M, Okumura H, Nakagawa N, Negishi T, Hashizume T, Nakajima M, Yokoi T. Metabolic Activation of Benzodiazepines by CYP3A4. Drug Metab Dispos 2008; 37:345-51. [DOI: 10.1124/dmd.108.024521] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Lee MD, Ayanoglu E, Gong L. Drug-induced changes in P450 enzyme expression at the gene expression level: a new dimension to the analysis of drug-drug interactions. Xenobiotica 2007; 36:1013-80. [PMID: 17118918 DOI: 10.1080/00498250600861785] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Drug-drug interactions (DDIs) caused by direct chemical inhibition of key drug-metabolizing cytochrome P450 enzymes by a co-administered drug have been well documented and well understood. However, many other well-documented DDIs cannot be so readily explained. Recent investigations into drug and other xenobiotic-mediated expression changes of P450 genes have broadened our understanding of drug metabolism and DDI. In order to gain additional information on DDI, we have integrated existing information on drugs that are substrates, inhibitors, or inducers of important drug-metabolizing P450s with new data on drug-mediated expression changes of the same set of cytochrome P450s from a large-scale microarray gene expression database of drug-treated rat tissues. Existing information on substrates and inhibitors has been updated and reorganized into drug-cytochrome P450 matrices in order to facilitate comparative analysis of new information on inducers and suppressors. When examined at the gene expression level, a total of 119 currently marketed drugs from 265 examined were found to be cytochrome P450 inducers, and 83 were found to be suppressors. The value of this new information is illustrated with a more detailed examination of the DDI between PPARalpha agonists and HMG-CoA reductase inhibitors. This paper proposes that the well-documented, but poorly understood, increase in incidence of rhabdomyolysis when a PPARalpha agonist is co-administered with a HMG-CoA reductase inhibitor is at least in part the result of PPARalpha-induced general suppression of drug metabolism enzymes in liver. The authors believe this type of information will provide insights to other poorly understood DDI questions and stimulate further laboratory and clinical investigations on xenobiotic-mediated induction and suppression of drug metabolism.
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Affiliation(s)
- M D Lee
- Iconix Biosciences, Mountain View, CA 94043, USA.
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Tanaka E, Nakamura T, Inomata S, Honda K. Effects of Premedication Medicines on the Formation of the CYP3A4-Dependent Metabolite of Ropivacaine, 2', 6'-Pipecoloxylidide, on Human Liver Microsomes in vitro. Basic Clin Pharmacol Toxicol 2006; 98:181-3. [PMID: 16445592 DOI: 10.1111/j.1742-7843.2006.pto_265.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Ropivacaine is a relatively new amide-type local anaesthetic, mainly used for surgery and postoperative pain relief. In this study we have investigated the interaction between the CYP3A4 metabolite of ropivacaine, 2',6'-pipecoloxylidide (PPX), and premedication with, i.e., psychotropic and antianxiety agents (diazepam, midazolam), hypnotics (thiamylal), local anaesthetics (lidocaine), depolarizing muscular relaxants (vecuronium), antihypertensive (clonidine) and H(2)-receptor antagonist (cimetidine) using human liver microsomes in vitro. The effects of the interaction between PPX and premedications were examined using a human liver microsomal preparation in vitro. The concentrations of ropivacaine and PPX were determined by HPLC with UV detection. The apparent Michaelis-Menten constant (Km) and the maximal velocity of total metabolic formation (V(max)) of PPX, the main metabolite of ropivacaine in human liver microsomes, were 17.7 (microM, mean) and 711 (nmol/min./mg protein, mean), respectively. Five premedications (diazepam, lidocaine, cimetidine, vecuronium and clonidine) did not inhibit ropivacaine metabolism in human liver microsomes at concentrations within the therapeutic range. However, midazolam and thiamylal weakly inhibited ropivacaine metabolism in competitive manner (IC(50) 7.8 microM and 250 microM, respectively). The results show lack of interaction between ropivacaine and seven premedication medicines within the therapeutic range of ropivacaine using human liver microsomes in vitro.
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Affiliation(s)
- Einosuke Tanaka
- Institute of Community Medicine, University of Tsukuba, Ibaraki-ken 305-8575, Japan.
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Nakazono K, Watanabe Y, Nakaya S, Asami Y, Masuhara K, Itoh F, Ogata H. Impairment state of cognitive performance and the affecting factors in outpatients following gastrointestinal endoscopy after single-dose diazepam. YAKUGAKU ZASSHI 2005; 125:307-14. [PMID: 15738630 DOI: 10.1248/yakushi.125.307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Diazepam is commonly used as premedicant for endoscopic procedures. Wide interindividual differences have been observed in the residual cognitive effects of the drug after gastrointestinal endoscopy. Our aim was to clarify the major factors, including pharmacokinetic factors, contributing to this wide variation in residual cognitive effect after gastrointestinal endoscopy in the study. Sixty-one outpatients undergoing gastrointestinal endoscopy participated in the study. Cognitive effects were evaluated in the diazepam group (n=52) by the digit symbol substitution test (DSST) twice before and 30 min after an intravenous administration of 5 mg diazepam; in the intervening time gastrointestinal endoscopy was performed. Plasma concentrations of diazepam were determined by HPLC. The control group (n=9) was tested by DSST in the same manner. The cognitive effects according to the change in DSST score was significantly decline in the diazepam group compared with the control group (by 0.2 versus -4.6; P=0.014). This prospective study confirmed that cognition was significantly impaired after gastrointestinal endoscopy by premedication to subjects with 5 mg diazepam. There were very wide variations in change in DSST score. However we could not identify the independent variables that best predicted DSST score difference in a multiple regression analysis for age, plasma albumin level, and plasma diazepam concentration 30 min after intravenous administration. We should pay attention to patients' individual states in cognitive performance following gastrointestinal endoscopy after single-dose diazepam.
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Affiliation(s)
- Kenichi Nakazono
- Course of Clinical Pharmacy, Graduate School of Pharmaceutical Sciences, Meiji Pharmaceutical University, Tokyo 204-8588, Japan
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Nagashima A, Tanaka E, Inomata S, Honda K, Misawa S. A study of the in vitro interaction between lidocaine and premedications using human liver microsomes*. J Clin Pharm Ther 2005; 30:185-8. [PMID: 15811173 DOI: 10.1111/j.1365-2710.2004.00617.x] [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: 11/30/2022]
Abstract
OBJECTIVE To investigate potential interactions between lidocaine (lignocaine) metabolism and premedication drugs, i.e. psychotropic and antianxiety agents (diazepam, midazolam), hypnotics (pentobarbital, thiamylal), depolarizing neuromuscular blocking agents (vecuronium, pancuronium and suxamethonium), an antihypertensive agent (clonidine) and an H2-receptor blocking agent (cimetidine) using human liver microsomes in vitro. METHODS The interaction effects between lidocaine and premedication were examined using human liver microsomal preparations and monitored for enzyme activity. The lidocaine and its main metabolite (monoethylglycinexylide) were measured by HPLC/UV. RESULTS Lidocaine metabolism was non-competitively inhibited by midazolam (Ki = 77.6 microM). Thiamylal was a competitive inhibitor of lidocaine metabolism (Ki = 885 microM). Cimethidine, pancuronium and vecuronium weakly inhibited lidocaine metabolism in a concentration-depend manner over the therapeutic range in human liver microsomes. On the contrary, suxamethonium, pentobarbital and clonidine did not inhibit lidocaine metabolism over the therapeutic range in human liver microsomes. CONCLUSION These results show that the interactions between lidocaine and midazolam and thiamylal are of potential toxicological and clinical significance.
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Affiliation(s)
- A Nagashima
- Institute of Community Medicine, University of Tsukuba, Ibaraki-ken, Japan
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Clarot F, Proust B, Vaz E, Goullé JP. Tramadol-benzodiazepines and buprenorphine-benzodiazepines: two potentially fatal cocktails? ACTA ACUST UNITED AC 2005; 10:125-6. [PMID: 15275034 DOI: 10.1016/s1353-1131(03)00039-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Hiratsuka M, Hinai Y, Konno Y, Nozawa H, Konno S, Mizugaki M. Three novel single nucleotide polymorphisms (SNPs) of the CYP2B6 gene in Japanese individuals. Drug Metab Pharmacokinet 2004; 19:155-8. [PMID: 15499182 DOI: 10.2133/dmpk.19.155] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We sequenced all exons and exon-intron junctions of the CYP2B6 gene from 200 Japanese individuals. We found three novel single nucleotide polymorphisms (SNPs) (1375A>G, 1427G>A and 1454A>T) causing amino acid substitutions (Met(459)Val, Gly(476)Asp and Gln(485)Leu in exon 9), respectively. The detected SNP was as follows: 1) SNP, 031226Hiratsuka01; GENE NAME, CYP2B6; ACCESSION NUMBER, AC023172; LENGTH, 25 base; 5'-CAGAACTTCTCCA/GTGGCCAGCCCCG-3'. 2) SNP, 031226Hiratsuka02; GENE NAME, CYP2B6; ACCESSION NUMBER, AC023172; LENGTH, 25 base; 5'-CCCAGGAGTGTGG/ATGTGGGCAAAAT-3'. 3) SNP, 031226Hiratsuka03; GENE NAME, CYP2B6; ACCESSION NUMBER, AC023172; LENGTH, 25 base; 5'-CCCCAACATACCA/TGATCCGCTTCCT-3'.
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Affiliation(s)
- Masahiro Hiratsuka
- Department of Clinical Pharmaceutics, Tohoku Pharmaceutical University, Sendai, Japan
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Micuda S, Mundlova L, Anzenbacherova E, Anzenbacher P, Chladek J, Fuksa L, Martinkova J. Inhibitory effects of memantine on human cytochrome P450 activities: prediction of in vivo drug interactions. Eur J Clin Pharmacol 2004; 60:583-9. [PMID: 15378224 DOI: 10.1007/s00228-004-0825-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2004] [Accepted: 07/21/2004] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The aim of the present study was to predict the drug interaction potential of memantine by elucidation of its inhibitory effects on cytochrome P450 enzymes using pooled human liver microsomes (HLM) and recombinant P450s. METHODS The inhibitory potency of memantine on CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 activities was examined with specific probe drugs in HLM and recombinant P450s. The in vivo drug interactions of memantine were predicted in vitro using the [ I]/([ I] + KI) values. RESULTS In HLM, memantine inhibited CYP2B6 and CYP2D6 activities, with KI (IC50) values of 76.7 (279.7) and 94.9 (368.7) microM, respectively. Both inhibitions were competitive. In addition, cDNA-expressed P450s were used to confirm these results. Memantine strongly inhibited recombinant CYP2B6 activity with IC50 ( KI) value of 1.12 (0.51) microM and activity of recombinant CYP2D6 with IC50 (KI) value of 242.4 (84.4) microM. With concentrations up to 1,000 microM, memantine showed no appreciable effect on CYP1A2, CYP2E1, CYP2C9, or CYP3A4 activities and a slight decrease of CYP2A6 and CYP2C19 activities. Based on [ I]/([ I] + KI) values calculated using peak total plasma concentration (or enzyme-available concentration in the liver) of memantine and the KI obtained in HLM, 1.3 (13.5), and 1.0% (11.2%), inhibition of the clearance of CYP2B6 and CYP2D6 substrates could be expected, respectively. Nevertheless, when considering KI values obtained from cDNA-expressed CYP2B6, as generally recommended, even 66.2% (95.9%) decrease in metabolism of coadministered CYP2B6 substrates could be anticipated. CONCLUSION Memantine exerts selective inhibition of CYP2B6 activity at clinically relevant concentrations, suggesting the potential for clinically significant drug interactions. Inhibition of other CYPs during memantine therapy is unlikely. Moreover, memantine represents a new, potent, selective inhibitor of recombinant CYP2B6, which may prove useful for screening purposes during early phases of in vitro drug metabolism studies with new chemical entities.
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Affiliation(s)
- Stanislav Micuda
- Department of Pharmacology, Medical Faculty of Charles University, Simkova 870, PO Box 38, 500 38, Hradec Kralove, Czech Republic.
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Niemi M, Backman JT, Fromm MF, Neuvonen PJ, Kivistö KT. Pharmacokinetic interactions with rifampicin : clinical relevance. Clin Pharmacokinet 2003; 42:819-50. [PMID: 12882588 DOI: 10.2165/00003088-200342090-00003] [Citation(s) in RCA: 513] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The antituberculosis drug rifampicin (rifampin) induces a number of drug-metabolising enzymes, having the greatest effects on the expression of cytochrome P450 (CYP) 3A4 in the liver and in the small intestine. In addition, rifampicin induces some drug transporter proteins, such as intestinal and hepatic P-glycoprotein. Full induction of drug-metabolising enzymes is reached in about 1 week after starting rifampicin treatment and the induction dissipates in roughly 2 weeks after discontinuing rifampicin. Rifampicin has its greatest effects on the pharmacokinetics of orally administered drugs that are metabolised by CYP3A4 and/or are transported by P-glycoprotein. Thus, for example, oral midazolam, triazolam, simvastatin, verapamil and most dihydropyridine calcium channel antagonists are ineffective during rifampicin treatment. The plasma concentrations of several anti-infectives, such as the antimycotics itraconazole and ketoconazole and the HIV protease inhibitors indinavir, nelfinavir and saquinavir, are also greatly reduced by rifampicin. The use of rifampicin with these HIV protease inhibitors is contraindicated to avoid treatment failures. Rifampicin can cause acute transplant rejection in patients treated with immunosuppressive drugs, such as cyclosporin. In addition, rifampicin reduces the plasma concentrations of methadone, leading to symptoms of opioid withdrawal in most patients. Rifampicin also induces CYP2C-mediated metabolism and thus reduces the plasma concentrations of, for example, the CYP2C9 substrate (S)-warfarin and the sulfonylurea antidiabetic drugs. In addition, rifampicin can reduce the plasma concentrations of drugs that are not metabolised (e.g. digoxin) by inducing drug transporters such as P-glycoprotein. Thus, the effects of rifampicin on drug metabolism and transport are broad and of established clinical significance. Potential drug interactions should be considered whenever beginning or discontinuing rifampicin treatment. It is particularly important to remember that the concentrations of many of the other drugs used by the patient will increase when rifampicin is discontinued as the induction starts to wear off.
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Affiliation(s)
- Mikko Niemi
- Department of Clinical Pharmacology, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland
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Abstract
Insomnia, an inability to initiate or maintain sleep, affects approximately one-third of the American population. Conventional benzodiazepines, such as triazolam and midazolam, were the treatment of choice for short-term insomnia for many years but are associated with adverse effects such as rebound insomnia, withdrawal and dependency. The newer hypnosedatives include zolpidem, zaleplon and zopiclone. These agents may be preferred over conventional benzodiazepines to treat short-term insomnia because they may be less likely to cause significant rebound insomnia or tolerance and are as efficacious as the conventional benzodiazepines. This review aims to summarise the published clinical drug interaction studies involving zolpidem, zaleplon and zopiclone. The pharmacokinetic and pharmacodynamic interactions that may be clinically important are highlighted. Clinical trials have studied potential interactions of zaleplon, zolpidem and zopiclone with the following types of drugs: cytochrome P450 (CYP) inducers (rifampicin), CYP inhibitors (azoles, ritonavir and erythromycin), histamine H(2) receptor antagonists (cimetidine and ranitidine), antidepressants, antipsychotics, antagonists of benzodiazepines and drugs causing sedation. Rifampicin significantly induced the metabolism of the newer hypnosedatives and decreased their sedative effects, indicating that a dose increase of these agents may be necessary when they are administered with rifampicin. Ketoconazole, erythromycin and cimetidine inhibited the metabolism of the newer hypnosedatives and enhanced their sedative effects, suggesting that a dose reduction may be required. Addition of ethanol to treatment with the newer hypnosedatives resulted in additive sedative effects without altering the pharmacokinetic parameters of the drugs. Compared with some of the conventional benzodiazepines, fewer clinically important interactions appear to have been reported in the literature with zaleplon, zolpidem and zopiclone. The fact that these drugs are newer to the market and have not been as extensively studied as the conventional benzodiazepines may be the reason for this. Another explanation may be a difference in CYP metabolism. While triazolam and midazolam are biotransformed almost entirely via CYP3A4, the newer hypnosedatives are biotransformed by several CYP isozymes in addition to CYP3A4, resulting in CYP3A4 inhibitors and inducers having a lesser effect on their biotransformation.
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Affiliation(s)
- Leah M Hesse
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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Jinno H, Tanaka-Kagawa T, Ohno A, Makino Y, Matsushima E, Hanioka N, Ando M. Functional characterization of cytochrome P450 2B6 allelic variants. Drug Metab Dispos 2003; 31:398-403. [PMID: 12642465 DOI: 10.1124/dmd.31.4.398] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cytochrome P450 (P450) 2B6 is a hepatic enzyme of potential importance for the metabolism of clinically used drugs and environmental or abused toxicants. Genetic polymorphisms of CYP2B6 (CYP2B6*2, CYP2B6*3, CYP2B6*4, CYP2B6*5, CYP2B6*6 and CYP2B6*7; wild-type, CYP2B6*1) were found previously in white and Japanese populations. In the present study, the goal was to investigate the effects of amino acid substitutions on CYP2B6 function. Wild-type (CYP2B6.1) and all of the known variants of CYP2B6 (CYP2B6.2, CYP2B6.3, CYP2B6.4, CYP2B6.5, CYP2B6.6, and CYP2B6.7) were transiently expressed in COS-1 cells, and their 7-ethoxy-4-trifluoromethylcoumarin O-deethylation activities were determined. The levels of the variant CYP2B6 proteins were relatively low compared with that of CYP2B6.1, although the differences were not significant. The activities of 7-ethoxy-4-trifluoromethylcoumarin O-deethylation on the basis of the CYP2B6 protein level at low (0.5 microM) and high (50 microM) substrate concentrations varied among wild-type and variant CYP2B6 proteins. All CYP2B6 enzymes showed typical Michaelis-Menten kinetics. The K(m) value of CYP2B6.6 was significantly higher than that of CYP2B6.1. Those CYP2B6 variants having a Lys262Arg substitution (CYP2B6.4, CYP2B6.6, and CYP2B6.7) showed increased values for V(max) and V(max)/K(m), whereas the kinetic parameters of CYP2B6.2 and CYP2B6.3 were not affected by the corresponding amino acid substitution. These results may mean that Lys262 in combination with other amino acid residues such as Gln172 and Arg487 is associated with the CYP2B6 function and that the genetic polymorphism of CYP2B6 leads to interindividual differences in xenobiotic metabolism.
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Affiliation(s)
- Hideto Jinno
- Division of Environmental Chemistry, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
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Nagashima A, Tanak E, Inomata S, Misawa S. A study of the in vitro clinical interaction between lidocaine and premedications using rat liver microsomes. Hum Exp Toxicol 2002; 21:453-6. [PMID: 12412639 DOI: 10.1191/0960327102ht279oa] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In this study, we have investigated the relationship between lidocaine metabolism and premedication, i.e., psychotropic and anti-anxiety agents (diazepam, midazolam), hypnotics (pentobarbital, thiamylal), depolarizing muscular relaxants (vecuronium, pancuronium and suxamethonium), an active anti-hypertensive (clonidine) and an H2 receptor antagonist (cimetidine) using rat hepatic microsomes in vitro. Lidocaine metabolism was noncompetitively inhibited by midazolam (Ki=29.0 microM). Thilamylal was a moderate competitive inhibitor of lidocaine metabolism (Ki=77.8 microM). Pentobarbital, diazepam and cimetidine weakly inhibited lidocaine metabolism formation in a concentration-dependent manner at high substrate concentrations. On the other hand, vecuronium, pancuronium, suxamethonium and clonidine did not inhibit lidocaine metabolism over the therapeutic range. These results show that the interaction between lidocaine and midazolam and thiamylal, catalyzed by a similar cytochrome P450, is of potential importance in toxicological and clinical studies.
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Affiliation(s)
- A Nagashima
- Institute of Community Medicine, University of Tsukuba, Japan
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Härtter S, Tybring G, Friedberg T, Weigmann H, Hiemke C. The N-demethylation of the doxepin isomers is mainly catalyzed by the polymorphic CYP2C19. Pharm Res 2002; 19:1034-7. [PMID: 12180536 DOI: 10.1023/a:1016478708902] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE This study was conducted to identify the cytochrome P450s (CYPs) responsible for the metabolism of the cis- and trans-isomers of the tricyclic antidepressant doxepin to its pharmacologically active N-desmethylmetabolite by in vitro techniques. METHODS The doxepin N-demethylation was studied by means of pooled human liver microsomes and chemical inhibitors, recombinant human (rh)-CYPs, and geno- and phenotyped human liver microsomes. RESULTS The N-demethylation of both isomers was inhibited most prominently by tranylcypromine (CYP2C19) to more than 50%. Furafylline (CYP1A2) and sulfaphenazole (CYP2C9) inhibited the N-demethylation to a lesser extent while quinidine (CYP2D6) or troleandomycine (CYP3A4) had no effect. Rh-CYP2C19, -CYP1A2, and -CYP2C9 were able to N-demethylate cis- and trans-doxepin. Only traces of trans-desmethyldoxepin were detectable when CYP3A4 was used. The maximum velocity in the cis- and transdoxepin N-demethylation was significantly (P < 0.05) lower in microsomes with low CYP2C19 activity (345 +/- 44 and 508 +/- 75 pmol/min/ mg protein, respectively) compared to those with high CYP2C19 activity (779 +/- 132 and 1,189 +/- 134 pmollmin/mg). CONCLUSION The present study demonstrates a significant contribution of the polymorphic CYP2C19 to the N-demethylation of doxepin. CYP2C9 and CYP1A2 play a minor role and CYP3A4 does not contribute substantially.
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Wang Q, Halpert JR. Combined three-dimensional quantitative structure-activity relationship analysis of cytochrome P450 2B6 substrates and protein homology modeling. Drug Metab Dispos 2002; 30:86-95. [PMID: 11744616 DOI: 10.1124/dmd.30.1.86] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Understanding the basis of the substrate specificity of cytochrome P450 2B6 (CYP2B6) is important for determining the role of this enzyme in drug metabolism and for predicting new substrates. Pharmacophores were generated for 16 structurally diverse CYP2B6 substrates with Catalyst after overlapping the reaction sites. Two pharmacophores were determined for the CYP2B6 binding site. Both include two hydrophobes and one hydrogen bond acceptor. The three-dimensional structure of CYP2B6 was then modeled based on the crystal structure of CYP2C5. Benzyloxyresorufin and 7-ethoxy-4-trifluoromethylcoumarin, the two lowest K(m) substrates in the training set, were then docked in the active site of CYP2B6. The pharmacophores were combined with the CYP2B6 model by comparing the docking results and the mapping of the two substrates with the pharmacophores. The results indicated that the active site of CYP2B6 complements the pharmacophores. The pharmacophores and the CYP2B6 model were used in conjunction to predict the K(m) values of substrates in a test set of five compounds and yielded satisfactory predictions for benzphetamine, cinnarizine, bupropion, and verapamil but not lidocaine. The CYP2B6 model, the pharmacophores, and the combination of the model with these pharmacophores provide insight into the interactions of CYP2B6 with substrates. The pharmacophores may be used as queries to search a database to predict new substrates for CYP2B6 when the reaction site is known (N- or O-dealkylation). For C-hydroxylation, the CYP2B6 model is helpful in evaluating the possible reaction sites in order for the pharmacophores to predict corresponding K(m) values.
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Affiliation(s)
- Qinmi Wang
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-1031, USA
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Venkatakrishnan K, Von Moltke LL, Greenblatt DJ. Human drug metabolism and the cytochromes P450: application and relevance of in vitro models. J Clin Pharmacol 2001; 41:1149-79. [PMID: 11697750 DOI: 10.1177/00912700122012724] [Citation(s) in RCA: 209] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The cytochromes P450 (CYPs) constitute a superfamily of hemoprotein enzymes that are responsible for the biotransformation of numerous xenobiotics, including therapeutic agents. Studies of the biochemical and enzymatic properties of these enzymes and their molecular genetics and regulation of gene expression and activity have greatly enhanced our understanding of several aspects of clinical pharmacology such as pharmacokinetic variability, drug toxicity, and drug interactions. This review evaluates the major human hepatic drug-metabolizing CYP enzymes and their clinically relevant substrates, inhibitors, and inducers. Also discussed are the molecular bases and clinical implications of genetic polymorphisms that affect the CYPs. Much of the information on the specificity of substrates and inhibitors of the CYP enzymes is derived from in vitro studies using human liver microsomes and heterologously expressed CYP enzymes. These methods are discussed, and guidelines are provided for designing enzyme kinetic and reaction phenotyping studies using multiple approaches. The strengths, weaknesses, and discrepancies among the different approaches are considered using representative examples. The mathematical models used in predicting the pharmacokinetic clearance of a drug from in vitro estimates of intrinsic clearance and the principles of quantitative in vitro-in vivo scaling of metabolic drug interactions are also discussed.
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Affiliation(s)
- K Venkatakrishnan
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, New England Medical Center Hospital, Boston, MA 02111, USA
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Shou M, Lu T, Krausz KW, Sai Y, Yang T, Korzekwa KR, Gonzalez FJ, Gelboin HV. Use of inhibitory monoclonal antibodies to assess the contribution of cytochromes P450 to human drug metabolism. Eur J Pharmacol 2000; 394:199-209. [PMID: 10771285 DOI: 10.1016/s0014-2999(00)00079-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Three inhibitory monoclonal antibodies specific to cytochrome P450 3A4/5 (CYP3A4/5), CYP2C8/9/19 and CYP2E1, respectively, were used to assess the contribution of the P450s to the metabolism of seven substrates in liver microsomes from 18 human donors, as measured by monoclonal antibody inhibition phenotyping of the substrate conversion to product(s). Metabolism of seven substrates by recombinant cytochromes P450 and human liver microsomes was performed in the presence of monoclonal antibodies and their metabolites were analyzed by high-performance liquid chromatography (HPLC) or gas chromatography-mass spectrophotometry (GC-MS) to measure the magnitude of inhibition. Our results showed that CYP3A4/5 contributes to testosterone 6beta-hydroxylation, taxol phenol formation, diazepam 3-hydroxylation, diazepam N-demethylation, and aflatoxin B1 3-hydroxylation in human liver by 79.2%, 81.5%, 73. 2%, 34.5% and 80%, respectively. CYP2E1 contributes to chlorzoxazone 6-hydroxylation, p-nitroanisole O-demethylation, and toluene hydroxylation by 45.8%, 27.7% and 44.2% respectively, and CYP2C8/9/19 contribute to diazepam N-demethylation by 30.6%. The additive contribution (75.3%) of human CYP3A and CYP2C to diazepam N-demethylation was also observed in the presence of both anti-CYP3A4/5 and anti-CYP2C8/9/19 monoclonal antibodies. The contribution of individual P450s to the specific metabolic reaction in human liver varies greatly in the individual donors and the substrates examined. Thus, inhibitory monoclonal antibodies could play a unique role in defining the single or subfamily of cytochrome P450 that is responsible for the metabolism of specific drugs.
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Affiliation(s)
- M Shou
- Department of Drug Metabolism, WP75A-203, Merck Research Laboratories, West Point, PA 19486, USA.
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Lewis DF, Lake BG, Dickins M, Eddershaw PJ, Tarbit MH, Goldfarb PS. Molecular modelling of CYP2B6, the human CYP2B isoform, by homology with the substrate-bound CYP102 crystal structure: evaluation of CYP2B6 substrate characteristics, the cytochrome b5 binding site and comparisons with CYP2B1 and CYP2B4. Xenobiotica 1999; 29:361-93. [PMID: 10375007 DOI: 10.1080/004982599238560] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
1. Molecular modelling studies of CYP2B isoforms from rat (CYP2B1), rabbit (CYP2B4) and man (CYP2B6) are reported, with particular emphasis on substrate interactions with the human CYP2B isoform, CYP2B6. 2. The findings represent an advance on our previous study that focused primarily on the rat CYP2B isoform, CYP2B1, and involved homology modelling with substrate-free CYP102. 3. The current work utilizes the recently published substrate-bound CYP102 crystal structure as a template for construction of the CYP2B subfamily isoforms and shows, in particular, that known CYP2B6 substrate specificity and regioselectivity can be rationalized by putative active site interactions.
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Affiliation(s)
- D F Lewis
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Guildford, UK.
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Shiraga T, Kaneko H, Iwasaki K, Tozuka Z, Suzuki A, Hata T. Identification of cytochrome P450 enzymes involved in the metabolism of zotepine, an antipsychotic drug, in human liver microsomes. Xenobiotica 1999; 29:217-29. [PMID: 10219963 DOI: 10.1080/004982599238623] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
1. Studies using human liver microsomes and recombinant human cytochrome P450 (P450) enzymes and flavin-containing monooxygenase (FMO) were performed to identify the enzymes responsible for the formation of zotepine metabolites in man. 2. Human liver microsomes produced four metabolites and a tentative order of importance was: norzotepine, 3-hydroxyzotepine, zotepine S-oxide and 2-hydroxyzotepine. Zotepine N-oxide was also detected, but it could not be quantified. 3. The rates of formation of the major metabolite, norzotepine, and zotepine S-oxide (at a substrate concentration of 20 microM) were significantly correlated with the testosterone 6beta-hydroxylase activities and CYP3A4 contents of the 12 different human liver microsomal samples. Inhibition studies with P450 enzyme selective inhibitors and anti-rat CYP3A2 antibodies also indicated a predominant role of CYP3A4 in the formation of norzotepine and zotepine S-oxide. Furafylline and sulphaphenazole inhibited the N-demethylation of zotepine by up to approximately 30%. 4. Correlation and inhibition data for the 2- and 3-hydroxylation of zotepine were consistent with the predominant role of CYP1A2 and 2D6 in the formation of these metabolites, respectively. 5. Recombinant CYP1A1, 1A2, 2B6, 2C19, 3A4 and 3A5 efficiently catalysed N-demethylation of zotepine. CYP1A1, 1A2, 2B6 and 3A4 were also active for S-oxidation. CYP1A2 and 2D6*1-Val374 efficiently produced 2-hydroxyzotepine and 3-hydroxyzotepine, respectively. Recombinant human FMO3 did not catalyse zotepine S-oxidation. 6. These results suggest that both the N-demethylation and S-oxidation of zotepine are mediated mainly by CYP3A4, and that CYP1A2 and 2D6 play an important role in the 2- and 3-hydroxylation of zotepine, respectively.
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Affiliation(s)
- T Shiraga
- Biopharmaceutical and Pharmacokinetic Research Laboratories, Fujisawa Pharmaceutical Co., Ltd, Osaka, Japan
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Reilly PE, Mason SR, Read MA. Human, rat and crocodile liver microsomal monooxygenase activities measured using diazepam and nifedipine: effects of CYP3A inhibitors and relationship to immunochemically detected CYP3A apoprotein. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART C, PHARMACOLOGY, TOXICOLOGY & ENDOCRINOLOGY 1999; 122:197-204. [PMID: 10190045 DOI: 10.1016/s0742-8413(98)10106-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Nifedipine oxidase and diazepam C3-hydroxylase were tested as activities for selectively measuring CYP3A enzymes using liver microsomes from male and female human organ donors, male and female Wistar rats and male and female estuarine crocodiles. The association between CYP3A enzymes and these monooxygenations was confirmed for the human samples. Male rat samples had lower specific contents of CYP3A apoprotein than the human samples but had equivalent (nifedipine) or higher (diazepam) monooxygenase specific activities. CYP3A apoprotein was undetectable in female rat samples which had very low activities towards both substrates. Enzyme inhibition studies showed that diazepam C3-hydroxylase of male rat liver was attributable to CYP3A but corresponding results for female rats suggested a contribution from non-CYP3A enzyme. Western blotting with immunochemical detection using anti-CYP3A4 IgG suggested the presence of putative CYP3A apoprotein in male and female crocodile liver samples and inhibition studies with diazepam as substrate suggested the presence of CYP3A subfamily monooxygenase activity in these enzyme preparations. Results for nifedipine oxidase with male and female rat liver and male crocodile liver suggested major contributions to catalysis from non-CYP3A enzymes. Inhibition studies suggested that a higher proportion of nifedipine oxidase in female crocodile liver may be attributable to the putative CYP3A enzyme(s) than in male crocodile liver. These results show the need for care in the assessment of CYP3A activity of fractionated tissues when using these substrates in cross-species studies and where gender is a variable.
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Affiliation(s)
- P E Reilly
- Department of Biochemistry University of Queensland, Brisbane, Australia.
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Venkatakrishnan K, von Moltke LL, Greenblatt DJ. Relative quantities of catalytically active CYP 2C9 and 2C19 in human liver microsomes: application of the relative activity factor approach. J Pharm Sci 1998; 87:845-53. [PMID: 9649353 DOI: 10.1021/js970435t] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The relative catalytic activities of CYP2C9 and CYP2C19 in human liver microsomes has been determined using the approach of relative activity factors (RAFs). Tolbutamide methylhydroxylation and S-mephenytoin 4'-hydroxylation were used as measures of CYP2C9 and CYP2C19 activity, respectively. The kinetics of these reactions were studied in human liver microsomes, in microsomes from human lymphoblastoid cells, and in insect cells expressing CYP2C9 and CYP2C19. RAFs were calculated as the ratio of Vmax (reaction velocity at saturating substrate concentrations) in human liver microsomes of the isoform-specific index reaction divided by the Vmax of the reaction catalyzed by the cDNA expressed isoform. RAFs were also determined for SUPERMIX, a commercially available mixture of cDNA expressed human drug metabolizing CYPs formulated to achieve a balance of enzyme activities similar to that found in human liver microsomes. Lymphoblast RAF2C9 in human liver microsomes ranged from 54 to 145 pmol CYP/mg protein (mean value: 87), while a value of 251 pmol CYP/mg protein was obtained for SUPERMIX. Insect cell RAF2C9 in human liver microsomes ranged from 1.6 to 143 pmol CYP/mg protein (mean value: 49), while a value of 201 pmol CYP/mg protein was obtained for SUPERMIX. Both lymphoblast and insect cell RAF2C19 in human liver microsomes ranged from 4 to 45 pmol CYP/mg protein (mean values: 29 and 28, respectively), while a value of 29 pmol CYP/mg protein was obtained for SUPERMIX. The nature of the cDNA expression system used had no effect on the kinetic parameters of CYP2C9 as a tolbutamide methylhydroxylase, or of CYP2C19 as a S-mephenytoin hydroxylase. However insect cell expressed CYP2C19 (which includes oxidoreductase) had substantially greater activity as a tolbutamide methylhydroxylase when compared to lymphoblast expressed CYP2C19. The ratio of mean lymphoblast-determined RAF2C9 to RAF2C19 in human livers was 3.0 (range 1.6-17.9; n = 10), while this ratio for SUPERMIX was 8.6. The ratio of mean insect cell-determined RAF2C9 to RAF2C19 in human livers was 1.7 (range 0.04-16.2; n = 10), while this ratio for SUPERMIX was 7.0. Neither ratio is in agreement with the 20:1 ratio of immunoquantified levels of CYP2C9 and 2C19 in human liver microsomes reported in previous studies. SUPERMIX may contain catalytically active CYP2C9 in levels higher than those in human liver microsomes.
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Affiliation(s)
- K Venkatakrishnan
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, New England Medical Center Hospital, Boston, Massachusetts, USA
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