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Al-Qurain AA, Upton RN, Tadros R, Roberts MS, Wiese MD. Population Pharmacokinetic Model for Tramadol and O-desmethyltramadol in Older Patients. Eur J Drug Metab Pharmacokinet 2022; 47:387-402. [PMID: 35167052 PMCID: PMC9050769 DOI: 10.1007/s13318-022-00756-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/16/2022] [Indexed: 11/24/2022]
Abstract
BACKGROUND AND OBJECTIVES Tramadol is commonly prescribed to manage chronic pain in older patients. However, there is a gap in the literature describing the pharmacokinetic parameters for tramadol and its active metabolite (O-desmethyltramadol [ODT]) in this population. The objective of this study was to develop and evaluate a population pharmacokinetic model for tramadol and ODT in older patients. METHODS Twenty-one patients who received an extended-release oral tramadol dose (25-100 mg) were recruited. Tramadol and ODT concentrations were determined using a validated liquid chromatography/tandem mass spectrometry method. A population pharmacokinetic model was developed using non-linear mixed-effects modelling. The performance of the model was assessed by visual predictive check. RESULTS A two-compartment, first-order absorption model with linear elimination best described the tramadol concentration data. The absorption rate constant was 2.96/h (between-subject variability [BSV] 37.8%), apparent volume of distribution for the central compartment (V1/F) was 0.373 l (73.8%), apparent volume of distribution for the peripheral compartment (V2/F) was 0.379 l (97.4%), inter-compartmental clearance (Q) was 0.0426 l/h (2.19%) and apparent clearance (CL/F) was 0.00604 l/h (6.61%). The apparent rate of metabolism of tramadol to ODT (kt) was 0.0492 l/h (78.5%) and apparent clearance for ODT (CLm) was 0.143 l/h (21.6%). Identification of Seniors at Risk score (ISAR) and creatinine clearance (CrCL) were the only covariates included in the final model, where a higher value for the ISAR increased the maximum concentration (Cmax) of tramadol and reduced the BSV in Q from 4.71 to 2.19%. A higher value of CrCL reduced tramadol Cmax and half-life (T1/2) and reduced the BSV in V2/F (from 148 to 97.4%) and in CL/F (from 78.9 to 6.61%). CONCLUSION Exposure to tramadol increased with increased frailty and reduced CrCL. Prescribers should consider patients frailty status and CrCL to minimise the risk of tramadol toxicity in such cohort of patients.
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Affiliation(s)
- Aymen A Al-Qurain
- UniSA: School of Pharmacy and Medical Science, Clinical and Health Sciences, University of South Australia, Adelaide, Australia. .,Pharmacy Department, Mohammed Almana College for Medical Sciences, Abdulrazaq Bin Hammam Street, Alsafa, Dammam, Saudi Arabia. .,Department of Health and Biomedical Innovation, University of South Australia, Adelaide, Australia.
| | - Richard N Upton
- UniSA: School of Pharmacy and Medical Science, Clinical and Health Sciences, University of South Australia, Adelaide, Australia
| | - Rami Tadros
- Department of Internal Medicine, Royal Adelaide Hospital, Adelaide, Australia
| | - Michael S Roberts
- UniSA: School of Pharmacy and Medical Science, Clinical and Health Sciences, University of South Australia, Adelaide, Australia.,Department of Therapeutics Research Centre, Diamantina Institute, Translational Research Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Michael D Wiese
- UniSA: School of Pharmacy and Medical Science, Clinical and Health Sciences, University of South Australia, Adelaide, Australia.,Department of Health and Biomedical Innovation, University of South Australia, Adelaide, Australia
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2
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Modelling and Differential Quantification of Electric Cell-Substrate Impedance Sensing Growth Curves. SENSORS 2021; 21:s21165286. [PMID: 34450726 PMCID: PMC8401457 DOI: 10.3390/s21165286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/26/2021] [Accepted: 08/02/2021] [Indexed: 11/29/2022]
Abstract
Measurement of cell surface coverage has become a common technique for the assessment of growth behavior of cells. As an indirect measurement method, this can be accomplished by monitoring changes in electrode impedance, which constitutes the basis of electric cell-substrate impedance sensing (ECIS). ECIS typically yields growth curves where impedance is plotted against time, and changes in single cell growth behavior or cell proliferation can be displayed without significantly impacting cell physiology. To provide better comparability of ECIS curves in different experimental settings, we developed a large toolset of R scripts for their transformation and quantification. They allow importing growth curves generated by ECIS systems, edit, transform, graph and analyze them while delivering quantitative data extracted from reference points on the curve. Quantification is implemented through three different curve fit algorithms (smoothing spline, logistic model, segmented regression). From the obtained models, curve reference points such as the first derivative maximum, segmentation knots and area under the curve are then extracted. The scripts were tested for general applicability in real-life cell culture experiments on partly anonymized cell lines, a calibration setup with a cell dilution series of impedance versus seeded cell number and finally IPEC-J2 cells treated with 1% and 5% ethanol.
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Kowalski JP, Pelletier RD, McDonald MG, Kelly EJ, Rettie AE. Pharmacokinetics, metabolism and off-target effects in the rat of 8-[(1H- benzotriazol-1-yl)amino]octanoic acid, a selective inhibitor of human cytochrome P450 4Z1: β-oxidation as a potential augmenting pathway for inhibition. Xenobiotica 2021; 51:901-915. [PMID: 33993844 DOI: 10.1080/00498254.2021.1930281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
8-[(1H-1,2,3-benzotriazol-1-yl)amino]octanoic acid (8-BOA) was recently identified as a selective and potent mechanism-based inactivator (MBI) of breast cancer-associated CYP4Z1 and exhibited favourable inhibitory activity in vitro, thus meriting in vivo characterization.The pharmacokinetics and metabolism of 8-BOA in rats was examined after a single IV bolus dose of 10 mg/kg. A biphasic time-concentration profile resulted in relatively low clearance and a prolonged elimination half-life.The major circulating metabolites identified in plasma were products of β-oxidation; congeners losing two and four methylene groups accounted for >50% of metabolites by peak area. The -(CH2)2 product was characterized previously as a CYP4Z1 MBI and so represents an active metabolite that may contribute to the desired pharmacological effect.Ex vivo analysis of total CYP content in rat liver and kidney microsomes showed that off-target CYP inactivation was minimal; liver microsomal probe substrate metabolism also demonstrated low off-target inactivation. Standard clinical chemistries provided no indication of acute toxicity.In silico simulations using the free concentration of 8-BOA in plasma suggested that the in vivo dose used here may effectively inactivate CYP4Z1 in a xenografted tumour.
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Affiliation(s)
- John P Kowalski
- Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Seattle, WA, USA.,Department of Drug Metabolism and Pharmacokinetics, Pfizer Boulder R&D, Boulder, CO, USA
| | - Robert D Pelletier
- Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Seattle, WA, USA
| | - Matthew G McDonald
- Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Seattle, WA, USA.,Department of Drug Metabolism and Pharmacokinetics, Pfizer Boulder R&D, Boulder, CO, USA
| | - Edward J Kelly
- Department of Pharmaceutics, School of Pharmacy, University of Washington, Seattle, WA, USA
| | - Allan E Rettie
- Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Seattle, WA, USA
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4
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Greenblatt DJ, Harmatz JS, Zhang Q, Chen Y, Shader RI. Slow Accumulation and Elimination of Diazepam and Its Active Metabolite With Extended Treatment in the Elderly. J Clin Pharmacol 2020; 61:193-203. [PMID: 32856316 DOI: 10.1002/jcph.1726] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 08/02/2020] [Indexed: 11/11/2022]
Abstract
Age-related changes in disposition of diazepam and its principal active metabolite, desmethyldiazepam (DMDZ), during and after extended dosage with diazepam were studied in healthy volunteers. Eight elderly subjects (ages 61-78 years) and 7 young subjects (21-33 years) received 2.5 mg of diazepam twice daily for 15 days. Predose (trough) concentrations of diazepam and DMDZ were measured during the 15 days of dosing, and in the postdosage washout period. Kinetic properties were determined by nonlinear regression using a sequential drug-to-metabolite pharmacokinetic model. Steady-state plasma concentrations of diazepam and DMDZ were 30% to 35% higher in elderly subjects compared to young volunteers, and steady-state clearances correspondingly lower, though differences did not reach significance. Large and significant differences were found between young and elderly groups in mean half-life of diazepam (31 vs 86 hours; P < .005) and DMDZ (40 vs 80 hours; P < .02). Half-life values from the multiple-dose study were closely correlated with values from previous single-dose studies of diazepam (R2 = 0.85) and DMDZ (R2 = 0.94) in the same subjects. With extended dosing of diazepam in the elderly, slow accumulation and delayed washout of diazepam and DMDZ is probable. After discontinuation, withdrawal or rebound effects are reduced in likelihood, but delayed recovery from sedative effects is possible due to slow elimination of active compounds. Safe treatment of elderly patients with diazepam is supported by understanding of age-related changes in pharmacologic and pharmacokinetic properties.
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Affiliation(s)
- David J Greenblatt
- Programs in Pharmacology and Drug Development and in Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Jerold S Harmatz
- Programs in Pharmacology and Drug Development and in Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Qingchen Zhang
- Programs in Pharmacology and Drug Development and in Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Yuxi Chen
- Programs in Pharmacology and Drug Development and in Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Richard I Shader
- Programs in Pharmacology and Drug Development and in Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, Massachusetts, USA
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Yu X, Fridman A, Bagchi A, Xu S, Kwasnjuk KA, Lu P, Cancilla MT. Metabolite Identification of Therapeutic Peptides and Proteins by Top-down Differential Mass Spectrometry and Metabolite Database Matching. Anal Chem 2020; 92:8298-8305. [PMID: 32402188 DOI: 10.1021/acs.analchem.0c00652] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
As metabolism impacts the efficacy and safety of therapeutic peptides and proteins (TPPs), understanding of the metabolic fate of TPPs is critical for their preclinical and clinical development. Despite the continued increase of new TPPs entering clinical trials, the metabolite identification (MetID) of these emerging modalities remains challenging. In the present study, we report an analytical workflow for MetID of TPPs. Using insulin detemir as an example, we demonstrated that top-down differential mass spectrometry (dMS) was able to distinguish and discover metabolites from complex biological matrices. For structural interpretation, we developed an algorithm to generate a complete and nonredundant theoretical metabolite database for a TPP of any topology (e.g., branched, multicyclic, etc.). Candidate structures of a metabolite were obtained by matching the monoisotopic mass of a dMS feature to the theoretical metabolite database. Finally, the MS/MS sequence tags enabled unambiguous characterization of metabolite structures when isobaric/isomeric candidates were present. This platform is widely applicable to TPPs with complex structures and will ultimately guide the structural optimization of TPPs in pharmaceutical development.
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Adiwidjaja J, Boddy AV, McLachlan AJ. Physiologically-Based Pharmacokinetic Predictions of the Effect of Curcumin on Metabolism of Imatinib and Bosutinib: In Vitro and In Vivo Disconnect. Pharm Res 2020; 37:128. [PMID: 32529309 DOI: 10.1007/s11095-020-02834-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Accepted: 04/26/2020] [Indexed: 12/14/2022]
Abstract
PURPOSE This study aimed to investigate the potential pharmacokinetic interactions between curcumin, imatinib and bosutinib, combining In Vitro and in silico methods. METHODS In Vitro metabolism of imatinib and bosutinib were investigated in pooled human liver microsomes and recombinant CYP3A4 enzyme in the presence and absence of curcumin and curcumin glucuronide using an LC-MS/MS assay for N-desmethyl metabolites. A physiologically-based pharmacokinetic (PBPK) model for curcumin formulated as solid lipid nanoparticles (SLN) was constructed using In Vitro glucuronidation kinetics and published clinical pharmacokinetic data. The potential effects of curcumin coadministration on systemic exposures of imatinib and bosutinib were predicted in silico using PBPK simulations. RESULTS Curcumin demonstrated potent reversible inhibition of cytochrome P450 (CYP)3A4-mediated N-demethylation of imatinib and bosutinib and CYP2C8-mediated metabolism of imatinib with inhibitory constants (ki,u) of ≤1.5 μmol. L-1. A confirmatory In Vitro study with paclitaxel, the 6α-hydroxylation of which is exclusively mediated by CYP2C8, was consistent with a potent inhibition of this enzyme by curcumin. Curcumin glucuronide also inhibited both CYP enzymes In Vitro, albeit to a lesser extent than that of curcumin. PBPK model simulations predicted that at recommended dosing regimens of SLN curcumin, coadministration would result in an increase in systemic exposures of imatinib and bosutinib of up to only 10%. CONCLUSION A PBPK model for curcumin in a SLN formulation was successfully developed. Although curcumin possesses a strong In Vitro inhibitory activity towards CYP3A4 and CYP2C8 enzymes, its interactions with imatinib and bosutinib were unlikely to be of clinical importance due to curcumin's poor bioavailability.
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Affiliation(s)
- Jeffry Adiwidjaja
- Sydney Pharmacy School, The University of Sydney, Sydney, NSW, 2006, Australia.
| | - Alan V Boddy
- School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA, 5001, Australia
- University of South Australia Cancer Research Institute, University of South Australia, Adelaide, SA, 5000, Australia
| | - Andrew J McLachlan
- Sydney Pharmacy School, The University of Sydney, Sydney, NSW, 2006, Australia
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7
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Callegari E, Varma MVS, Obach RS. Prediction of Metabolite-to-Parent Drug Exposure: Derivation and Application of a Mechanistic Static Model. Clin Transl Sci 2019; 13:520-528. [PMID: 31880865 PMCID: PMC7214656 DOI: 10.1111/cts.12734] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 11/27/2019] [Indexed: 12/02/2022] Open
Abstract
In the development of new drugs, the prediction of metabolite‐to‐parent plasma exposure ratio in humans prior to administration in a clinical study has emerged as an important need. In this work, we derived a mechanistic static model based on first principles to estimate metabolite‐to‐parent plasma exposure ratio, considering the contribution of liver and gut metabolism and drug transport. Knowledge (or assumptions) of mechanisms of clearance and organs involved is required. Input parameters needed included intrinsic clearance, fraction of clearance to the metabolite of interest, various binding values, and, in some cases, active transport clearance. The principles are illustrated with four drugs that yield six metabolites, with one in which clearance is dependent on a pathway subject to genetic polymorphism. Overall, the approach yielded metabolite‐to‐parent ratios within about twofold of the actual values and, thus, can be valuable in decision making in the drug development process.
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Affiliation(s)
- Ernesto Callegari
- Pharmacokinetics, Pharmacodynamics, & Metabolism, Medicine Design, Pfizer Inc., Groton, Connecticut, USA
| | - Manthena V S Varma
- Pharmacokinetics, Pharmacodynamics, & Metabolism, Medicine Design, Pfizer Inc., Groton, Connecticut, USA
| | - R Scott Obach
- Pharmacokinetics, Pharmacodynamics, & Metabolism, Medicine Design, Pfizer Inc., Groton, Connecticut, USA
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8
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Population Pharmacokinetics of Artemether, Dihydroartemisinin, and Lumefantrine in Rwandese Pregnant Women Treated for Uncomplicated Plasmodium falciparum Malaria. Antimicrob Agents Chemother 2018; 62:AAC.00518-18. [PMID: 30061282 PMCID: PMC6153812 DOI: 10.1128/aac.00518-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 07/23/2018] [Indexed: 12/12/2022] Open
Abstract
The artemisinin-based combination therapy artemether-lumefantrine is commonly used in pregnant malaria patients. However, the effect of pregnancy-related changes on exposure is unclear, and pregnancy has been associated with decreased efficacy in previous studies. This study aimed to characterize the population pharmacokinetics of artemether, its active metabolite dihydroartemisinin, and lumefantrine in 22 Rwandese pregnant women in their second (n = 11) or third (n = 11) trimester with uncomplicated Plasmodium falciparum malaria. These patients were enrolled from Rwamagana district hospital and received the standard fixed oral dose combination of 80 mg of artemether and 480 mg of lumefantrine twice daily for 3 days. Venous plasma concentrations were quantified for all three analytes using liquid chromatography coupled with tandem mass spectroscopy, and data were analyzed using nonlinear mixed-effects modeling. Lumefantrine pharmacokinetics was described by a flexible but highly variable absorption, with a mean absorption time of 4.04 h, followed by a biphasic disposition model. The median area under the concentration-time curve from 0 h to infinity (AUC0-∞) for lumefantrine was 641 h · mg/liter. Model-based simulations indicated that 11.7% of the study population did not attain the target day 7 plasma concentration (280 ng/ml), a threshold associated with increased risk of recrudescence. The pharmacokinetics of artemether was time dependent, and the autoinduction of its clearance was described using an enzyme turnover model. The turnover half-life was predicted to be 30.4 h. The typical oral clearance, which started at 467 liters/h, increased 1.43-fold at the end of treatment. Simulations suggested that lumefantrine pharmacokinetic target attainment appeared to be reassuring in Rwandese pregnant women, particularly compared to target attainment in Southeast Asia. Larger cohorts will be required to confirm this finding.
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9
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Ufuk A, Kosa RE, Gao H, Bi YA, Modi S, Gates D, Rodrigues AD, Tremaine LM, Varma MVS, Houston JB, Galetin A. In Vitro-In Vivo Extrapolation of OATP1B-Mediated Drug-Drug Interactions in Cynomolgus Monkey. J Pharmacol Exp Ther 2018; 365:688-699. [PMID: 29643253 DOI: 10.1124/jpet.118.247767] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 04/06/2018] [Indexed: 12/31/2022] Open
Abstract
Hepatic organic anion-transporting polypeptides (OATP) 1B1 and 1B3 are clinically relevant transporters associated with significant drug-drug interactions (DDIs) and safety concerns. Given that OATP1Bs in cynomolgus monkey share >90% degree of gene and amino acid sequence homology with human orthologs, we evaluated the in vitro-in vivo translation of OATP1B-mediated DDI risk using this preclinical model. In vitro studies using plated cynomolgus monkey hepatocytes showed active uptake Km values of 2.0 and 3.9 µM for OATP1B probe substrates, pitavastatin and rosuvastatin, respectively. Rifampicin inhibited pitavastatin and rosuvastatin active uptake in monkey hepatocytes with IC50 values of 3.0 and 0.54 µM, respectively, following preincubation with the inhibitor. Intravenous pharmacokinetics of 2H4-pitavastatin and 2H6-rosuvastatin (0.2 mg/kg) and the oral pharmacokinetics of cold probes (2 mg/kg) were studied in cynomolgus monkeys (n = 4) without or with coadministration of single oral ascending doses of rifampicin (1, 3, 10, and 30 mg/kg). A rifampicin dose-dependent reduction in i.v. clearance of statins was observed. Additionally, oral pitavastatin and rosuvastatin plasma exposure increased up to 19- and 15-fold at the highest dose of rifampicin, respectively. Use of in vitro IC50 obtained following 1 hour preincubation with rifampicin (0.54 µM) predicted correctly the change in mean i.v. clearance and oral exposure of statins as a function of mean unbound maximum plasma concentration of rifampicin. This study demonstrates quantitative translation of in vitro OATP1B IC50 to predict DDIs using cynomolgus monkey as a preclinical model and provides further confidence in application of in vitro hepatocyte data for the prediction of clinical OATP1B-mediated DDIs.
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Affiliation(s)
- Ayşe Ufuk
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, University of Manchester, Manchester, United Kingdom (A.U., J.B.H., A.G.); and Pharmacokinetics, Dynamics, and Metabolism (R.E.K., H.G., Y.-A.B., A.D.R., L.M.T., M.V.S.V.) and Research Formulations, Pharmaceutical Sciences (S.M., D.G.), Medicine Design, Pfizer Worldwide R&D, Groton, Connecticut
| | - Rachel E Kosa
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, University of Manchester, Manchester, United Kingdom (A.U., J.B.H., A.G.); and Pharmacokinetics, Dynamics, and Metabolism (R.E.K., H.G., Y.-A.B., A.D.R., L.M.T., M.V.S.V.) and Research Formulations, Pharmaceutical Sciences (S.M., D.G.), Medicine Design, Pfizer Worldwide R&D, Groton, Connecticut
| | - Hongying Gao
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, University of Manchester, Manchester, United Kingdom (A.U., J.B.H., A.G.); and Pharmacokinetics, Dynamics, and Metabolism (R.E.K., H.G., Y.-A.B., A.D.R., L.M.T., M.V.S.V.) and Research Formulations, Pharmaceutical Sciences (S.M., D.G.), Medicine Design, Pfizer Worldwide R&D, Groton, Connecticut
| | - Yi-An Bi
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, University of Manchester, Manchester, United Kingdom (A.U., J.B.H., A.G.); and Pharmacokinetics, Dynamics, and Metabolism (R.E.K., H.G., Y.-A.B., A.D.R., L.M.T., M.V.S.V.) and Research Formulations, Pharmaceutical Sciences (S.M., D.G.), Medicine Design, Pfizer Worldwide R&D, Groton, Connecticut
| | - Sweta Modi
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, University of Manchester, Manchester, United Kingdom (A.U., J.B.H., A.G.); and Pharmacokinetics, Dynamics, and Metabolism (R.E.K., H.G., Y.-A.B., A.D.R., L.M.T., M.V.S.V.) and Research Formulations, Pharmaceutical Sciences (S.M., D.G.), Medicine Design, Pfizer Worldwide R&D, Groton, Connecticut
| | - Dana Gates
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, University of Manchester, Manchester, United Kingdom (A.U., J.B.H., A.G.); and Pharmacokinetics, Dynamics, and Metabolism (R.E.K., H.G., Y.-A.B., A.D.R., L.M.T., M.V.S.V.) and Research Formulations, Pharmaceutical Sciences (S.M., D.G.), Medicine Design, Pfizer Worldwide R&D, Groton, Connecticut
| | - A David Rodrigues
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, University of Manchester, Manchester, United Kingdom (A.U., J.B.H., A.G.); and Pharmacokinetics, Dynamics, and Metabolism (R.E.K., H.G., Y.-A.B., A.D.R., L.M.T., M.V.S.V.) and Research Formulations, Pharmaceutical Sciences (S.M., D.G.), Medicine Design, Pfizer Worldwide R&D, Groton, Connecticut
| | - Larry M Tremaine
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, University of Manchester, Manchester, United Kingdom (A.U., J.B.H., A.G.); and Pharmacokinetics, Dynamics, and Metabolism (R.E.K., H.G., Y.-A.B., A.D.R., L.M.T., M.V.S.V.) and Research Formulations, Pharmaceutical Sciences (S.M., D.G.), Medicine Design, Pfizer Worldwide R&D, Groton, Connecticut
| | - Manthena V S Varma
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, University of Manchester, Manchester, United Kingdom (A.U., J.B.H., A.G.); and Pharmacokinetics, Dynamics, and Metabolism (R.E.K., H.G., Y.-A.B., A.D.R., L.M.T., M.V.S.V.) and Research Formulations, Pharmaceutical Sciences (S.M., D.G.), Medicine Design, Pfizer Worldwide R&D, Groton, Connecticut
| | - J Brian Houston
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, University of Manchester, Manchester, United Kingdom (A.U., J.B.H., A.G.); and Pharmacokinetics, Dynamics, and Metabolism (R.E.K., H.G., Y.-A.B., A.D.R., L.M.T., M.V.S.V.) and Research Formulations, Pharmaceutical Sciences (S.M., D.G.), Medicine Design, Pfizer Worldwide R&D, Groton, Connecticut
| | - Aleksandra Galetin
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, University of Manchester, Manchester, United Kingdom (A.U., J.B.H., A.G.); and Pharmacokinetics, Dynamics, and Metabolism (R.E.K., H.G., Y.-A.B., A.D.R., L.M.T., M.V.S.V.) and Research Formulations, Pharmaceutical Sciences (S.M., D.G.), Medicine Design, Pfizer Worldwide R&D, Groton, Connecticut
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Abstract
This tutorial explains the pharmacokinetics of a prodrug and its active metabolite (or parent drug) using a two-step, consecutive, first-order irreversible reaction as a basic model for prodrug metabolism. In this model, the prodrug is metabolized and produces the parent drug, which is subsequently eliminated. The mathematical expressions for pharmacokinetic parameters were derived step by step. In addition, we visualized these expressions to help understand the relationship between pharmacokinetic parameters easily. For the elimination rate-limited and formation rate-limited metabolism, we analyzed the plasma drug concentration versus time curve of a prodrug administered intravenously.
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Affiliation(s)
- Seungil Cho
- Molecular Diagnostics and Imaging Center, School of Medicine, Kyungpook National University; Clinical Trial Center, Kyungpook National University Hospital, Daegu 41944, Korea
| | - Young-Ran Yoon
- Molecular Diagnostics and Imaging Center, School of Medicine, Kyungpook National University; Clinical Trial Center, Kyungpook National University Hospital, Daegu 41944, Korea
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Effects of dronedarone, amiodarone and their active metabolites on sequential metabolism of arachidonic acid to epoxyeicosatrienoic and dihydroxyeicosatrienoic acids. Biochem Pharmacol 2017; 146:188-198. [DOI: 10.1016/j.bcp.2017.09.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 09/22/2017] [Indexed: 12/23/2022]
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12
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Obach RS, Lin J, Kimoto E, Duvvuri S, Nicholas T, Kadar EP, Tremaine LM, Sawant-Basak A. Estimation of Circulating Drug Metabolite Exposure in Human Using In Vitro Data and Physiologically Based Pharmacokinetic Modeling: Example of a High Metabolite/Parent Drug Ratio. Drug Metab Dispos 2017; 46:89-99. [PMID: 29150544 DOI: 10.1124/dmd.117.078279] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 11/14/2017] [Indexed: 12/15/2022] Open
Abstract
(R)-4-((4-(((4-((tetrahydrofuran-3-yl)oxy)benzo[d]isoxazol-3-yl)oxy)methyl)piperidin-1-yl)methyl)tetrahydro-2H-pyran-4-ol (TBPT), a serotonin-4 receptor partial agonist, is metabolized to two metabolites: an N-dealkylation product [(R)-3-(piperidin-4-ylmethoxy)-4-((tetrahydrofuran-3-yl)oxy)benzo[d]isoxazole (M1)] and a cyclized oxazolidine structure [7-(((4-(((R)-tetrahydrofuran-3-yl)oxy)benzo[d]isoxazol-3-yl)oxy)methyl)octahydro-3H (M2)]. After administration of TBPT to humans the exposure to M1 was low and the exposure to M2 was high, relative to the parent drug, despite this being the opposite in vitro. In this study, projection of the plasma metabolite/parent (M/P) ratios for M1 and M2 was attempted using in vitro metabolism, binding, and permeability data in static and dynamic physiologically based pharmacokinetic (PBPK) models. In the static model, the fraction of parent clearance yielding the metabolite (which also required taking into account secondary metabolites of M1 and M2), the clearance of the metabolites and parent, and an estimate of the availability of the metabolites from the liver were combined to yield estimated parent/metabolite ratios of 0.32 and 23 for M1 and M2, respectively. PBPK modeling that used in vitro and physicochemical data input yielded estimates of 0.26 and 20, respectively. The actual values were 0.12 for M1/TBPT and 58 for M2/TBPT. Thus, the ratio for M1 was overpredicted, albeit at values less than unity. The ratio for M2/TBPT was underpredicted, and the high ratio of 58 may exceed a limiting ceiling of the approach. Nevertheless, when considered in the context of determining whether a potential circulating metabolite may be quantitatively important prior to administration of a drug for the first time to humans, the approaches succeeded in highlighting the importance of M2 (M/P ratio >> 1) relative to M1, despite M1 being much greater than M2 in vitro.
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Affiliation(s)
- R Scott Obach
- Department of Pharmacokinetics, Dynamics, and Drug Metabolism, Pfizer Inc., Groton, Connecticut (RSO, JL, EK, EPK, and RSO), and Cambridge, Massachusetts (ASB); and Department of Clinical Pharmacology, Pfizer Inc., Cambridge, Massachusetts (SD and TN)
| | - Jian Lin
- Department of Pharmacokinetics, Dynamics, and Drug Metabolism, Pfizer Inc., Groton, Connecticut (RSO, JL, EK, EPK, and RSO), and Cambridge, Massachusetts (ASB); and Department of Clinical Pharmacology, Pfizer Inc., Cambridge, Massachusetts (SD and TN)
| | - Emi Kimoto
- Department of Pharmacokinetics, Dynamics, and Drug Metabolism, Pfizer Inc., Groton, Connecticut (RSO, JL, EK, EPK, and RSO), and Cambridge, Massachusetts (ASB); and Department of Clinical Pharmacology, Pfizer Inc., Cambridge, Massachusetts (SD and TN)
| | - Sridhar Duvvuri
- Department of Pharmacokinetics, Dynamics, and Drug Metabolism, Pfizer Inc., Groton, Connecticut (RSO, JL, EK, EPK, and RSO), and Cambridge, Massachusetts (ASB); and Department of Clinical Pharmacology, Pfizer Inc., Cambridge, Massachusetts (SD and TN)
| | - Timothy Nicholas
- Department of Pharmacokinetics, Dynamics, and Drug Metabolism, Pfizer Inc., Groton, Connecticut (RSO, JL, EK, EPK, and RSO), and Cambridge, Massachusetts (ASB); and Department of Clinical Pharmacology, Pfizer Inc., Cambridge, Massachusetts (SD and TN)
| | - Eugene P Kadar
- Department of Pharmacokinetics, Dynamics, and Drug Metabolism, Pfizer Inc., Groton, Connecticut (RSO, JL, EK, EPK, and RSO), and Cambridge, Massachusetts (ASB); and Department of Clinical Pharmacology, Pfizer Inc., Cambridge, Massachusetts (SD and TN)
| | - Larry M Tremaine
- Department of Pharmacokinetics, Dynamics, and Drug Metabolism, Pfizer Inc., Groton, Connecticut (RSO, JL, EK, EPK, and RSO), and Cambridge, Massachusetts (ASB); and Department of Clinical Pharmacology, Pfizer Inc., Cambridge, Massachusetts (SD and TN)
| | - Aarti Sawant-Basak
- Department of Pharmacokinetics, Dynamics, and Drug Metabolism, Pfizer Inc., Groton, Connecticut (RSO, JL, EK, EPK, and RSO), and Cambridge, Massachusetts (ASB); and Department of Clinical Pharmacology, Pfizer Inc., Cambridge, Massachusetts (SD and TN)
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Nguyen HQ, Lin J, Kimoto E, Callegari E, Tse S, Obach RS. Prediction of Losartan-Active Carboxylic Acid Metabolite Exposure Following Losartan Administration Using Static and Physiologically Based Pharmacokinetic Models. J Pharm Sci 2017; 106:2758-2770. [DOI: 10.1016/j.xphs.2017.03.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 03/22/2017] [Accepted: 03/27/2017] [Indexed: 01/02/2023]
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Nguyen HQ, Callegari E, Obach RS. The Use of In Vitro Data and Physiologically-Based Pharmacokinetic Modeling to Predict Drug Metabolite Exposure: Desipramine Exposure in Cytochrome P4502D6 Extensive and Poor Metabolizers Following Administration of Imipramine. ACTA ACUST UNITED AC 2016; 44:1569-78. [PMID: 27440861 DOI: 10.1124/dmd.116.071639] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 07/18/2016] [Indexed: 02/06/2023]
Abstract
Major circulating drug metabolites can be as important as the drugs themselves in efficacy and safety, so establishing methods whereby exposure to major metabolites following administration of parent drug can be predicted is important. In this study, imipramine, a tricyclic antidepressant, and its major metabolite desipramine were selected as a model system to develop metabolite prediction methods. Imipramine undergoes N-demethylation to form the active metabolite desipramine, and both imipramine and desipramine are converted to hydroxylated metabolites by the polymorphic enzyme CYP2D6. The objective of the present study is to determine whether the human pharmacokinetics of desipramine following dosing of imipramine can be predicted using static and dynamic physiologically-based pharmacokinetic (PBPK) models from in vitro input data for CYP2D6 extensive metabolizer (EM) and poor metabolizer (PM) populations. The intrinsic metabolic clearances of parent drug and metabolite were estimated using human liver microsomes (CYP2D6 PM and EM) and hepatocytes. Passive diffusion clearance of desipramine, used in the estimation of availability of the metabolite, was predicted from passive permeability and hepatocyte surface area. The predicted area under the curve (AUCm/AUCp) of desipramine/imipramine was 12- to 20-fold higher in PM compared with EM subjects following i.v. or oral doses of imipramine using the static model. Moreover, the PBPK model was able to recover simultaneously plasma profiles of imipramine and desipramine in populations with different phenotypes of CYP2D6. This example suggested that mechanistic PBPK modeling combined with information obtained from in vitro studies can provide quantitative solutions to predict in vivo pharmacokinetics of drugs and major metabolites in a target human population.
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Affiliation(s)
- Hoa Q Nguyen
- Department of Pharmacokinetics, Dynamics, and Metabolism, Pfizer Global Research and Development, Groton, Connecticut
| | - Ernesto Callegari
- Department of Pharmacokinetics, Dynamics, and Metabolism, Pfizer Global Research and Development, Groton, Connecticut
| | - R Scott Obach
- Department of Pharmacokinetics, Dynamics, and Metabolism, Pfizer Global Research and Development, Groton, Connecticut
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Nguyen HQ, Kimoto E, Callegari E, Obach RS. Mechanistic Modeling to Predict Midazolam Metabolite Exposure from In Vitro Data. ACTA ACUST UNITED AC 2016; 44:781-91. [PMID: 26956641 DOI: 10.1124/dmd.115.068601] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 03/07/2016] [Indexed: 12/12/2022]
Abstract
Methods to predict the pharmacokinetics of drugs in humans from in vitro data have been established, but corresponding methods to predict exposure to circulating metabolites are unproven. The objective of this study was to use in vitro methods combined with static and dynamic physiologically based pharmacokinetic (PBPK) models to predict metabolite exposures, using midazolam and its major metabolites as a test system. Intrinsic clearances (CLint) of formation of individual metabolites were determined using human liver microsomes. Metabolic CLintof hydroxymidazolam metabolites via oxidation and glucuronidation were also determined. Passive diffusion intrinsic clearances of hydroxymidazolam metabolites were determined using sandwich cultured human hepatocytes and the combination of this term along with the metabolic CLint, and liver blood flow was used to estimate the fraction of the metabolite that can enter the systemic circulation after formation in the liver. The metabolite/parent drug area under the plasma concentration-time curve ratio (AUCm/AUCp) was predicted using a static model relating the fraction of midazolam clearance to each metabolite, the clearance rates of midazolam and hydroxymidazolam metabolites, and the availability of the metabolites. Additionally, the human disposition of midazolam metabolites was simulated using a SimCYP PBPK model. Both approaches yielded AUCm/AUCpratios that were in agreement with the in vivo ratios. This study shows that in vivo midazolam metabolite exposure can be predicted from in vitro data and PBPK modeling. This study emphasized the importance of metabolite systemic availability from its tissue of formation, which remains a challenge to quantitative prediction.
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Affiliation(s)
- Hoa Q Nguyen
- Pfizer Global Research and Development, Department of Pharmacokinetics, Dynamics, and Metabolism, Groton, Connecticut
| | - Emi Kimoto
- Pfizer Global Research and Development, Department of Pharmacokinetics, Dynamics, and Metabolism, Groton, Connecticut
| | - Ernesto Callegari
- Pfizer Global Research and Development, Department of Pharmacokinetics, Dynamics, and Metabolism, Groton, Connecticut
| | - R Scott Obach
- Pfizer Global Research and Development, Department of Pharmacokinetics, Dynamics, and Metabolism, Groton, Connecticut
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Gasparetto JC, Peccinini RG, de Francisco TMG, Cerqueira LB, Campos FR, Pontarolo R. A kinetic study of the main guaco metabolites using syrup formulation and the identification of an alternative route of coumarin metabolism in humans. PLoS One 2015; 10:e0118922. [PMID: 25757073 PMCID: PMC4355590 DOI: 10.1371/journal.pone.0118922] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 01/14/2015] [Indexed: 11/19/2022] Open
Abstract
For decades guaco species have been empirically used for the treatment of respiratory diseases. However, studies have shown that the toxic and therapeutic effects of the main guaco metabolites are dose-dependent, and none clinical study was done to evaluate the behavior of these substances in humans. In this work, a pilot study measuring the kinetic profile of the main guaco metabolites was performed leading to the knowledge of an alternative route of coumarin metabolism in humans. Initial screenings demonstrated that the administration of 60 mL of guaco syrup (single dose) did not provide sufficient levels of coumarin (COU), 7-hydroxycoumarin (7-HCOU), o-coumaric acid (OCA) and kaurenoic acid (KAU). The pharmacokinetic parameters were calculated by orally administering 60 mL of guaco syrup spiked with 1500 mg of COU. The kinetic study demonstrated that the plasmatic levels of 7-HCOU (considered the main metabolite of COU) were 10 times lower than the levels of COU, and the kinetic profile of 7-HCOU suggests sequential metabolism in the liver with low access of 7-HCOU to the systemic circulation. The study also demonstrated that OCA is one of the main bioavailable metabolites of COU. Therefore, the hydrolysis of the lactone ring forming a carboxylated compound is one of the possible routes of COU metabolism in humans. The half-lives of COU, 7-HCOU and OCA were approximately 4.0, 1.0 and 3.0 h, respectively and there was evidence that the recommended dosage of guaco syrup did not provide sufficient levels of COU, 7-HCOU or OCA to obtain a bronchodilation effect. Clinical studies are necessary to prove the efficacy and safety of products based on guaco.
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Affiliation(s)
| | - Rosângela Gonçalves Peccinini
- Department of Natural Active Principles and Toxicology, Universidade Estadual Paulista Julio de Mesquita Filho, Araraquara, SP, Brazil
| | | | | | | | - Roberto Pontarolo
- Department of Pharmacy, Universidade Federal do Paraná, Curitiba, PR, Brazil
- * E-mail:
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Linares OA, Fudin J, Schiesser WE, Daly Linares AL, Boston RC. CYP2D6 Phenotype-Specific Codeine Population Pharmacokinetics. J Pain Palliat Care Pharmacother 2015; 29:4-15. [DOI: 10.3109/15360288.2014.997854] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Abstract
This chapter describes the types of irreversible inhibition of drug-metabolizing enzymes and the methods commonly employed to quantify the irreversible inhibition and subsequently predict the extent and time course of clinically important drug-drug interactions.
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Affiliation(s)
- Michael Mohutsky
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
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Fan J, de Lannoy IA. Pharmacokinetics. Biochem Pharmacol 2014; 87:93-120. [DOI: 10.1016/j.bcp.2013.09.007] [Citation(s) in RCA: 169] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 09/06/2013] [Accepted: 09/09/2013] [Indexed: 11/29/2022]
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Wang Z, Lin YS, Dickmann LJ, Poulton EJ, Eaton DL, Lampe JW, Shen DD, Davis CL, Shuhart MC, Thummel KE. Enhancement of hepatic 4-hydroxylation of 25-hydroxyvitamin D3 through CYP3A4 induction in vitro and in vivo: implications for drug-induced osteomalacia. J Bone Miner Res 2013; 28:1101-16. [PMID: 23212742 PMCID: PMC3609874 DOI: 10.1002/jbmr.1839] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 10/12/2012] [Accepted: 11/26/2012] [Indexed: 01/08/2023]
Abstract
Long-term therapy with certain drugs, especially cytochrome P450 (P450; CYP)-inducing agents, confers an increased risk of osteomalacia that is attributed to vitamin D deficiency. Human CYP24A1, CYP3A4, and CYP27B1 catalyze the inactivation and activation of vitamin D and have been implicated in the adverse drug response. In this study, the inducibility of these enzymes and monohydroxylation of 25-hydroxyvitamin D3 (25OHD3) were evaluated after exposure to P450-inducing drugs. With human hepatocytes, treatment with phenobarbital, hyperforin, carbamazepine, and rifampin significantly increased the levels of CYP3A4, but not CYP24A1 or CYP27B1 mRNA. In addition, rifampin pretreatment resulted in an 8-fold increase in formation of the major metabolite of 25OHD3, 4β,25(OH)2D3. This inductive effect was blocked by the addition of 6',7'-dihydroxybergamottin, a selective CYP3A4 inhibitor. With human renal proximal tubular HK-2 cells, treatment with the same inducers did not alter CYP3A4, CYP24A1, or CYP27B1 expression. 24R,25(OH)2 D3 was the predominant monohydroxy metabolite produced from 25OHD3, but its formation was unaffected by the inducers. With healthy volunteers, the mean plasma concentration of 4β,25(OH)2D3 was increased 60% (p < 0.01) after short-term rifampin administration. This was accompanied by a statistically significant reduction in plasma 1α,25(OH)2D3 (-10%; p = 0.03), and a nonsignificant change in 24R,25(OH)2D3 (-8%; p = 0.09) levels. Further analysis revealed a negative correlation between the increase in 4β,25(OH)2D3 and decrease in 1α,25(OH)2D3 levels. Examination of the plasma monohydroxy metabolite/25OHD3 ratios indicated selective induction of the CYP3A4-dependent 4β-hydroxylation pathway of 25OHD3 elimination. These results suggest that induction of hepatic CYP3A4 may be important in the etiology of drug-induced osteomalacia.
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Affiliation(s)
- Zhican Wang
- Department of Pharmaceutics, University of Washington, Seattle, WA, USA
| | - Yvonne S. Lin
- Department of Pharmaceutics, University of Washington, Seattle, WA, USA
| | - Leslie J. Dickmann
- Biochemistry and Biophysics Group, Department of Pharmacokinetics and Drug Metabolism, Amgen, Seattle, WA, USA
| | - Emma-Jane Poulton
- Department of Environmental Health Sciences, and Medicine, University of Washington, Seattle, WA, USA
| | - David L. Eaton
- Department of Environmental Health Sciences, and Medicine, University of Washington, Seattle, WA, USA
| | - Johanna W. Lampe
- Public Health Science Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Danny D. Shen
- Department of Pharmaceutics, University of Washington, Seattle, WA, USA
| | - Connie L. Davis
- Division of Nephrology, University of Washington, Seattle, WA, USA
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Abstract
Characterization of the circulating metabolites for a new chemical entity in humans is essential for safety assessment, an understanding of their contributions to pharmacologic activities, and their potential involvement in drug-drug interactions. This review examines the abundance of metabolites relative to the total parent drug [metabolite-to-parent (M/P) ratio] from 125 drugs in relation to their structural and physicochemical characteristics, lipoidal permeability, protein binding, and fractional formation from parent (fm). Our analysis suggests that fm is the major determinant of total drug M/P ratio for amine, alcohol, N- and S-oxide, and carboxylic acid metabolites. Passage from the hepatocyte to systemic circulation does not appear to be limiting owing to the vast majority of metabolites formed being relatively lipid permeable. In some cases, active transport plays an important role in this process (e.g., carboxylic acid metabolites). Differences in total parent drug clearance and metabolite clearance are attenuated by the reduction in lipophilicity introduced by the metabolic step and resultant compensatory changes in unbound clearance and protein binding. A small subclass of these drugs (e.g., terfenadine) is unintentional prodrugs with very high parent drug clearance, resulting in very high M/P ratios. In contrast, arenol metabolites show a more complex relationship with fm due largely to the new metabolic routes (conjugation) available to the metabolite compared with the parent drug molecule. For these metabolites, a more thorough understanding of the elimination clearance of the metabolite is critical to discern the likelihood of whether the phenol will constitute a major circulating metabolite.
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Affiliation(s)
- Cho-Ming Loi
- Pfizer, Inc., 10646 Science Center Drive, San Diego, CA 92121, USA.
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Obach RS. Pharmacologically active drug metabolites: impact on drug discovery and pharmacotherapy. Pharmacol Rev 2013; 65:578-640. [PMID: 23406671 DOI: 10.1124/pr.111.005439] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Metabolism represents the most prevalent mechanism for drug clearance. Many drugs are converted to metabolites that can retain the intrinsic affinity of the parent drug for the pharmacological target. Drug metabolism redox reactions such as heteroatom dealkylations, hydroxylations, heteroatom oxygenations, reductions, and dehydrogenations can yield active metabolites, and in rare cases even conjugation reactions can yield an active metabolite. To understand the contribution of an active metabolite to efficacy relative to the contribution of the parent drug, the target affinity, functional activity, plasma protein binding, membrane permeability, and pharmacokinetics of the active metabolite and parent drug must be known. Underlying pharmacokinetic principles and clearance concepts are used to describe the dispositional behavior of metabolites in vivo. A method to rapidly identify active metabolites in drug research is described. Finally, over 100 examples of drugs with active metabolites are discussed with regard to the importance of the metabolite(s) in efficacy and safety.
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Affiliation(s)
- R Scott Obach
- Pfizer Inc., Eastern Point Rd., Groton, CT 06340, USA.
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Fleishaker JC, Smith TC, Friedman HL, Hulst LK. Separation of the Pharmacokinetic/Pharmacodynamic Properties of Oral and IV Adinazolam Mesylate and N-Desmethyladinazolam Mesylate in Healthy Volunteers. ACTA ACUST UNITED AC 2012. [DOI: 10.1007/bf03258394] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Evidence of CYP3A allosterism in vivo: analysis of interaction between fluconazole and midazolam. Clin Pharmacol Ther 2011; 91:442-9. [PMID: 22048224 PMCID: PMC3830930 DOI: 10.1038/clpt.2011.178] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The allosteric effect of fluconazole (effector) on the formation of 1’-hydroxymidazolam (1’-OH-MDZ) and 4-hydroxymidazolam (4-OH-MDZ) from the CYP3A4/5 substrate, midazolam (MDZ), was examined in healthy volunteers. Following pre-treatment of fluconazole, AUC4-OH/AUCMDZ increased 35–62%, while AUC1’-OH/AUCMDZ decreased 5–37%; AUC1’-OH/AUC4-OH ratio decreased 46–58% by fluconazole and had no association with CYP3A5 genotype. 1’-OH-MDZ formation in vitro was more susceptible than 4-OH-MDZ formation to inhibition by fluconazole. Fluconazole decreased the intrinsic formation clearance ratio of 1’-OH-MDZ/4-OH-MDZ to an extent that was quantitatively comparable to in vivo observations. The elimination clearance of midazolam metabolites appeared unaffected by fluconazole. This study demonstrated that fluconazole alters midazolam product formation both in vivo and in vitro in a manner consistent with an allosteric interaction. The 1'-OH-MDZ/4-OH-MDZ ratio may serve as a biomarker of such interactions between midazolam, CYP3A4/5 and other putative effectors.
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Lutz JD, Fujioka Y, Isoherranen N. Rationalization and prediction of in vivo metabolite exposures: the role of metabolite kinetics, clearance predictions and in vitro parameters. Expert Opin Drug Metab Toxicol 2011; 6:1095-109. [PMID: 20557268 DOI: 10.1517/17425255.2010.497487] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
IMPORTANCE OF THE FIELD Due to growing concerns over toxic or active metabolites, significant efforts have been focused on qualitative identification of potential in vivo metabolites from in vitro data. However, limited tools are available to quantitatively predict their human exposures. AREAS COVERED IN THIS REVIEW Theory of clearance predictions and metabolite kinetics is reviewed together with supporting experimental data. In vitro and in vivo data of known circulating metabolites and their parent drugs were collected and the predictions of in vivo exposures of the metabolites were evaluated. WHAT THE READER WILL GAIN The theory and data reviewed will be useful in early identification of human metabolites that will circulate at significant levels in vivo and help in designing in vivo studies that focus on characterization of metabolites. It will also assist in rationalization of metabolite-to-parent ratios used as markers of specific enzyme activity. TAKE HOME MESSAGE The relative importance of a metabolite in comparison to the parent compound as well as other metabolites in vivo can only be predicted using the metabolite's in vitro formation and elimination clearances, and the in vivo disposition of a metabolite can only be rationalized when the elimination pathways of that metabolite are known.
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Affiliation(s)
- Justin D Lutz
- Department of Pharmaceutics, University of Washington, School of Pharmacy, H272 Health Science Building, Box 357610, Seattle, WA 98195-7610, USA
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Zhou ZW, Zhou SF. Application of mechanism-based CYP inhibition for predicting drug-drug interactions. Expert Opin Drug Metab Toxicol 2009; 5:579-605. [PMID: 19466877 DOI: 10.1517/17425250902926099] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND A mechanism-based inhibition of CYPs is characterized by NADPH-, time- and concentration-dependent enzyme inactivation and substrate protection. A significant inactivation of CYPs and particularly the main human hepatic and intestinal CYPs could result in clinical drug-drug interactions (DDIs) and adverse drug reactions. OBJECTIVE To address whether DDIs owing to mechanism-based CYP inhibition is predictable based on in vitro inhibitory data. METHOD Medline (by means of PubMed up to 26 March 2009) has been searched using proper relevant terms. RESULT/CONCLUSION It is possible to predict DDIs caused by mechanism-based CYP inhibition, although the in vitro data do not necessarily translate directly into relative extents of inhibition in vivo because in vivo clinical consequences depend on additional factors that are not easily accounted for in vitro and for reversible inhibition. Incorporation of other important parameters such as CYP degradation rate (k(deg)), relative contribution of the CYP inactivated to the victim drug elimination (f(m(CYP))) and inhibition of intestinal CYP-mediated first-pass metabolism of the object drug (F'(gut)/F(gut) ratio) into the prediction models significantly improves the prediction. Uncertainty of the prediction is mainly from the variability in the estimates of these critical parameters.
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Affiliation(s)
- Zhi-Wei Zhou
- RMIT University, Discipline of Chinese Medicine, School of Health Sciences, Bundoora, Victoria, Australia
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Tonn GR, Wong SG, Wong SC, Johnson MG, Ma J, Cho R, Floren LC, Kersey K, Berry K, Marcus AP, Wang X, Van Lengerich B, Medina JC, Pearson PG, Wong BK. An Inhibitory Metabolite Leads to Dose- and Time-Dependent Pharmacokinetics of (R)-N-{1-[3-(4-Ethoxy-phenyl)-4-oxo-3,4-dihydro-pyrido[2,3-d]pyrimidin-2-yl]-ethyl}-N-pyridin-3-yl-methyl-2-(4-trifluoromethoxy-phenyl)-acetamide (AMG 487) in Human Subjects After Multiple Dosing. Drug Metab Dispos 2008; 37:502-13. [DOI: 10.1124/dmd.108.021931] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
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Prueksaritanont T, Lin JH, Baillie TA. Complicating factors in safety testing of drug metabolites: Kinetic differences between generated and preformed metabolites. Toxicol Appl Pharmacol 2006; 217:143-52. [PMID: 17055014 DOI: 10.1016/j.taap.2006.08.009] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2006] [Revised: 08/25/2006] [Accepted: 08/29/2006] [Indexed: 12/15/2022]
Abstract
This paper aims to provide a scientifically based perspective on issues surrounding the proposed toxicology testing of synthetic drug metabolites as a means of ensuring adequate nonclinical safety evaluation of drug candidates that generate metabolites considered either to be unique to humans or are present at much higher levels in humans than in preclinical species. We put forward a number of theoretical considerations and present several specific examples where the kinetic behavior of a preformed metabolite given to animals or humans differs from that of the corresponding metabolite generated endogenously from its parent. The potential ramifications of this phenomenon are that the results of toxicity testing of the preformed metabolite may be misleading and fail to characterize the true toxicological contribution of the metabolite when formed from the parent. It is anticipated that such complications would be evident in situations where (a) differences exist in the accumulation of the preformed versus generated metabolites in specific tissues, and (b) the metabolite undergoes sequential metabolism to a downstream product that is toxic, leading to differences in tissue-specific toxicity. Owing to the complex nature of this subject, there is a need to treat drug metabolite issues in safety assessment on a case-by-case basis, in which a knowledge of metabolite kinetics is employed to validate experimental paradigms that entail administration of preformed metabolites to animal models.
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Prueksaritanont T, Kuo Y, Tang C, Li C, Qiu Y, Lu B, Strong-Basalyga K, Richards K, Carr B, Lin JH. In vitro and in vivo CYP3A64 induction and inhibition studies in rhesus monkeys: a preclinical approach for CYP3A-mediated drug interaction studies. Drug Metab Dispos 2006; 34:1546-55. [PMID: 16782766 DOI: 10.1124/dmd.106.009878] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In this study, induction and inhibition of rhesus monkey CYP3A64 versus human CYP3A4 were characterized in vitro, and the corresponding pharmacokinetic consequences were evaluated in rhesus monkeys. In monkey hepatocytes, rifampin markedly induced CYP3A64 mRNA (EC50 = 0.5 microM; Emax = 6-fold) and midazolam (MDZ) 1'-hydroxylase activity (EC50 = 0.2 microM; Emax = 2-fold). Compound A (N-[2(R)-hydroxy-1(S)-indanyl-5-[2(S)-(1,1-dimethylethylaminocarbonyl)-4-[(furo[2,3-b]pyridin-5-yl)-methyl]piperazin-1-yl]-4(S)-hydroxy-2(R)-phenylmethylpentanamide), a known potent and mechanism-based inhibitor of CYP3A4, strongly inhibited the formation of 1'-hydroxy MDZ by recombinant CYP3A64 in a concentration- and time-dependent manner (KI = 0.25 microM; k(inact) = 0.4 min(-1)). Similar corresponding results also were obtained with human CYP3A4 in the presence of rifampin or compound A. In rhesus monkeys, MDZ exhibited a relatively high metabolic clearance (primarily via 1'-hydroxylation followed by glucuronidation) and a low hepatic availability (Fh = 16%). Consistent with the induction of hepatic metabolism of a high-clearance compound, pretreatment with rifampin (18 mg/kg p.o. for 5 days) did not significantly affect the i.v. kinetics of MDZ, but caused a pronounced reduction (approximately 10-fold) in the systemic exposure to MDZ and, consequently, its Fh following intrahepatic portal vein administration (i.pv.) of MDZ. A comparable extent of the pharmacokinetic interaction also was obtained after a 1.8 mg/kg rifampin dose. Also consistent with the in vitro CYP3A64 inhibition finding, compound A (6 mg/kg i.v.) markedly increased (10-fold) the i.pv. administered MDZ exposure. At the doses studied, plasma concentrations of rifampin or compound A reached or exceeded their respective in vitro EC50 or KI values. These findings suggest the potential applicability of the in vitro-in vivo relationship approach in rhesus monkeys for studying CYP3A-mediated interactions in humans.
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Panhard X, Goujard C, Legrand M, Taburet AM, Diquet B, Mentré F. Population pharmacokinetic analysis for nelfinavir and its metabolite M8 in virologically controlled HIV-infected patients on HAART. Br J Clin Pharmacol 2005; 60:390-403. [PMID: 16187971 PMCID: PMC1884828 DOI: 10.1111/j.1365-2125.2005.02456.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2004] [Accepted: 01/26/2005] [Indexed: 11/27/2022] Open
Abstract
AIMS To describe the pharmacokinetics of nelfinavir and its main metabolite M8 in HIV-infected patients with a sustained virological response, to characterize the effect of covariates and to estimate inter- and intra-individual variability in the pharmacokinetics. METHODS Three hundred and twenty concentrations of both nelfinavir and M8 were measured in 46 patients enrolled in the COPHAR 1-ANRS 102 study. Blood samples were taken at a first visit (one sample before drug administration and four samples at fixed times after) and at a second visit 1 to 3 months later (one before and one 3 h after drug administration). The data from both visits on nelfinavir and M8 were modelled jointly in all patients using a population approach. RESULTS A one-compartment model with first-order absorption and elimination best described nelfinavir data, with an additional compartment incorporating a first order rate-constant describing the metabolism of the drug to M8. For nelfinavir, the apparent volume of distribution (V/F ) (95% confidence interval for the mean), was 309 l (185, 516), the absorption rate constant (k(a)) was 0.4 h(-1) (0.2, 0.8), and the apparent clearance (CL/F ) was 37.3 l h(-1) (32, 44). For M8, V(m) /(Fk(m)) and CL(m)/(Fk(m)) were 866 l h(-1) (351, 2161) and 1670 l (965, 2894), respectively. The interindividual variabilities were 34.9%, 34.3% and 62.2% for V/F, CL/F and CL(m)/(Fk(m)), respectively. The interoccasion variability was 27.8% for CL/F. The mean half-lives were 05.38 h and 00.44 h for nelfinavir and M8, respectively. Significant but opposite effects of comedication with zidovudine were found on nelfinavir CL/F and M8 CL(m)/(Fk(m)), but they were not considered to be clinically relevant. CONCLUSIONS A joint model was found to describe adequately nelfinavir and M8 concentrations and was used to estimate pharmacokinetic parameters for M8. The model can be used to build reference pharmacokinetic profiles for therapeutic drug monitoring of the drug.
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Affiliation(s)
- X Panhard
- INSERM U738, Department of Epidemiology, Biostatistics and Clinical research, AP-HP, Bichat University Hospital, Paris, France.
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Kharasch ED, Whittington D, Hoffer C, Krudys K, Craig K, Vicini P, Sheffels P, Lalovic B. Paradoxical Role of Cytochrome P450 3A in the Bioactivation and Clinical Effects of Levo-??-Acetylmethadol. Clin Pharmacokinet 2005; 44:731-51. [PMID: 15966756 DOI: 10.2165/00003088-200544070-00005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
OBJECTIVE Levo-alpha-acetylmethadol (LAAM, levacetylmethadol) is a long-acting opioid agonist used for the prevention of opioid withdrawal. LAAM undergoes sequential N-demethylation to norLAAM and dinorLAAM, which are more potent and longer-acting than LAAM. Hepatic and intestinal microsomal N-demethylation in vitro is catalysed mainly by cytochrome P450 (CYP) 3A4; however, the role of CYP3A in LAAM disposition in humans in vivo is unknown. This investigation tested the hypothesis that CYP3A induction (or inhibition) would increase (or decrease) LAAM metabolism and bioactivation and, thus, clinical effects. It also related changes in LAAM disposition during enzyme inhibition or induction to any changes in pharmacological effect. METHODS Healthy volunteers (n = 13) completed the three-way, randomised, balanced crossover study. Subjects received oral LAAM (0.25 mg/kg) after CYP3A induction (rifampicin [rifampin]), inhibition (troleandomycin) or nothing (controls). Plasma and urine LAAM, norLAAM and dinorLAAM were determined by electrospray high-performance liquid chromatography/mass spectrometry (HPLC/MS). Dark-adapted pupil diameter change from baseline (miosis) was the LAAM effect measure. Results were analysed by noncompartmental methods and by a combined pharmacokinetic/pharmacodynamic model. RESULTS Compared with controls, CYP3A induction (or inhibition) decreased (or increased) plasma LAAM concentrations and mean area under the plasma concentration-time curve from time zero to infinity (AUC(infinity) 199 +/- 91 [control] versus 11.3 +/- 4.0 [rifampicin] and 731 +/- 229 ng . h/mL [troleandomycin]; p < 0.05), and increased (or decreased) median formation clearances of norLAAM (1740 versus 14 100 and 302 mL/h/kg; p < 0.05) and dinorLAAM (636 versus 7840 and 173 mL/h/kg; p < 0.05). Surprisingly, however, CYP3A induction (or inhibition) decreased (or increased) mean plasma metabolite AUC from 0 to 96 hours (AUC(96)) [norLAAM + dinorLAAM] (859 +/- 241 versus 107 +/- 48 and 1185 +/- 179 ng . h/mL; p < 0.05) and clinical effects (mean miosis AUC(96) 128 +/- 40 versus 22.5 +/- 14.9 and 178 +/- 81 mm . h; p < 0.05). Clinical effects were best correlated with plasma norLAAM concentrations. CONCLUSION CYP3A mediates human LAAM N-demethylation and bioactivation to norLAAM and dinorLAAM in vivo. Paradoxically, however, CYP3A induction decreased and inhibition increased LAAM active metabolite concentrations and clinical effects. This suggests a CYP3A-mediated metabolic pathway leading to inactive metabolites, which predominates over CYP3A-dependent bioactivation. These results highlight the need for clinical investigations to validate in vitro drug metabolism studies.
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Affiliation(s)
- Evan D Kharasch
- Department of Anesthesiology, University of Washington, Seattle, Washington 98195, USA.
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Martinez M, Langston C, Martin T, Conner D. Challenges associated with the evaluation of veterinary product bioequivalence: an AAVPT perspective. J Vet Pharmacol Ther 2002; 25:201-20. [PMID: 12081616 DOI: 10.1046/j.1365-2885.2002.00407.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Generic Animal Drug Patent Term Restoration Act (GADPTRA) enacted in 1988 provided the same benefits to animal drug products that were granted to human generic products. It has been over 13 years since the GADPTRA was enacted, and veterinary drug sponsors and regulators have gained enormous insight and experience into some of the unique challenges associated with the determination of product bioequivalence for veterinary dosage forms. Moreover, advances in information and technology have opened both new issues that must be addressed and new mechanisms for demonstrating product bioequivalence. While many aspects of the existing Center for Veterinary Medicine Bioequivalence Guidance continue to provide invaluable guidance to the animal drug industry, there are also aspects of this guidance that are being called into question. Therefore, during the 2001 annual meeting of the American Academy of Veterinary Pharmacology and Therapeutics, participants were asked to address issues and concerns associated with the evaluation of veterinary product bioequivalence. This manuscript provides a summary of the concerns and discussions that transpired.
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Affiliation(s)
- M Martinez
- Center for Veterinary Medicine, Food and Drug Administration, Rockville, MD 20855, USA.
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Abstract
The half-life of a drug, which expresses a change in concentration in units of time, is perhaps the most easily understood pharmacokinetic parameter and provides a succinct description of many concentration-time profiles. The calculation of a half-life implies a linear, first-order, time-invariant process. No drug perfectly obeys such assumptions, although in practise this is often a valid approximation and provides invaluable quantitative information. Nevertheless, the physiological processes underlying half-life should not be forgotten. The concept of clearance facilitates the interpretation of factors affecting drug elimination, such as enzyme inhibition or renal impairment. Relating clearance to the observed concentration-time profile is not as naturally intuitive as is the case with half-life. As such, these 2 approaches to parameterising a linear pharmacokinetic model should be viewed as complementary rather than alternatives. The interpretation of pharmacokinetic parameters when there are multiple disposition phases is more challenging. Indeed, in any pharmacokinetic model, the half-lives are only one component of the parameters required to specify the concentration-time profile. Furthermore, pharmacokinetic parameters are of little use without a dose history. Other factors influencing the relevance of each disposition phase to clinical end-points must also be considered. In summarising the pharmacokinetics of a drug, statistical aspects of the estimation of a half-life are often overlooked. Half-lives are rarely reported with confidence intervals or measures of variability in the population, and some approaches to this problem are suggested. Half-life is an important summary statistic in pharmacokinetics, but care must be taken to employ it appropriately in the context of dose history and clinically relevant pharmacodynamic end-points.
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Affiliation(s)
- J G Wright
- Cancer Research Unit, University of Newcastle, Medical School, Newcastle upon Tyne, England.
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Mihara K, Svensson US, Tybring G, Hai TN, Bertilsson L, Ashton M. Stereospecific analysis of omeprazole supports artemisinin as a potent inducer of CYP2C19. Fundam Clin Pharmacol 2000; 13:671-5. [PMID: 10626755 DOI: 10.1111/j.1472-8206.1999.tb00379.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The purpose of the study was to determine the enantiomer pharmacokinetics of omeprazole and 5-hydroxy-omeprazole before and after administration of the antimalarial artemisinin to confirm artemisinin's ability to induce CYP2C19. Nine healthy male Vietnamese subjects were given a single 20 mg dose of omeprazole orally 1 week before (day - 7) artemisinin administration. Artemisinin was then given orally (500 mg) for 7 days (days 1-7). On days 1 and 7, a single 20 mg dose of omeprazole was coadministered with artemisinin. After a washout period of 6 days, a single 20 mg dose of omeprazole was again administered together with a single 500 mg of artemisinin (day 14). Stereoselective pharmacokinetics of omeprazole and 5-hydroxyomeprazole was determined on days of omeprazole administration. Seven days of artemisinin administration significantly decreased the AUC of both omeprazole enantiomers (day 7), compared with day 1 (P < 0.001). All values were normalized after the washout period. Artemisinin increased the AUC ratio of R-5-hydroxyomeprazole/R-omeprazole significantly (P < 0.01) on day 7. The AUC ratio of omeprazole sulphone/S-omeprazole did not differ between study days. Artemisinin decreased the AUC of S-omeprazole to the same extent as that of R-omeprazole in extensive CYP2C19 metabolizers. suggesting that artemisinin induces a different enzyme in addition to CYP2C19. These results support and strengthen earlier findings that artemisinin induces CYP2C19 as well as at least one enzyme other than CYP3A4.
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Affiliation(s)
- K Mihara
- Department of Medical Laboratory Sciences and Technology, Karolinska Institute, Huddinge University Hospital, Sweden
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Reed-Hagen AE, Tsuchiya M, Shimada K, Wentland JA, Obach RS. Pharmacokinetics of ezlopitant, a novel non-peptidic neurokinin-1 receptor antagonist in preclinical species and metabolite kinetics of the pharmacologically active metabolites. Biopharm Drug Dispos 1999; 20:429-39. [PMID: 10951432 DOI: 10.1002/1099-081x(199912)20:9<429::aid-bdd209>3.0.co;2-d] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The pharmacokinetics of ezlopitant were determined in the rat, gerbil, guinea pig, ferret, dog and monkey after intravenous and oral administration. In general, ezlopitant is marked by high clearance values that approach or exceed hepatic blood flow values, moderate to high values for steady-state volume of distribution (3. 9-28 L/kg), and terminal phase half-life values ranging from 0.6 h in the guinea pig to 7.7 h in the rat. Oral bioavailability ranged from <0.2% (guinea pig) to 28% (dog). Data from portal vein cannulated dogs suggested that 37% of an oral dose of ezlopitant enters the portal vein as an unchanged drug in this species. Ezlopitant is metabolized to two pharmacologically active metabolites, an alkene (CJ-12 458) and a benzyl alcohol (CJ-12 764). After administration of the parent compound, CJ-12 764 was found in greater abundance than CJ-12 458 in all species examined. Ezlopitant and CJ-12 458 were highly protein bound in plasma (or serum), whereas the protein binding of CJ-12 764 was somewhat lower. Measurement of the kinetics of ezlopitant, CJ-12 458 and CJ-12 764 in the cerebrospinal fluid (CSF) of dogs demonstrated that all three compounds can partition into the CSF, and thereby, be capable of contributing to centrally mediated pharmacological effects. Thus, these data suggest that the pharmacological activity exhibited by ezlopitant in preclinical species in vivo is likely a result of the parent compound plus the active metabolites. Furthermore, the contributions of ezlopitant and the active metabolites to pharmacological activity probably varies with the identity of the model species, as well as the dose and route of ezlopitant administration.
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Affiliation(s)
- A E Reed-Hagen
- Drug Metabolism Department, Central Research, Pfizer, Inc., Groton, CT 06340, USA
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Hassan M, Svensson US, Ljungman P, Björkstrand B, Olsson H, Bielenstein M, Abdel-Rehim M, Nilsson C, Johansson M, Karlsson MO. A mechanism-based pharmacokinetic-enzyme model for cyclophosphamide autoinduction in breast cancer patients. Br J Clin Pharmacol 1999; 48:669-77. [PMID: 10594468 PMCID: PMC2014348 DOI: 10.1046/j.1365-2125.1999.00090.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS This study investigated the pharmacokinetics of cyclophosphamide (CP) and its main metabolite 4-hydroxycyclophosphamide (4-OH-CP) in patients with breast cancer undergoing high dose chemotherapy prior to autologous stem cell transplantation. An enzyme turn-over model was also developed to study the time course of cyclophosphamide induction. METHODS Fourteen patients received a combination of CP (6 g m-2 ), thiotepum (500 mg m-2 ) and carboplatin (800 mg m-2 ) as a 96 h infusion. Plasma concentrations of CP and 4-OH-CP were determined with h.p.l.c. and a pharmacokinetic and enzyme turn-over model applied to data using NONMEM. RESULTS CP plasma concentrations were described by a two-compartment model with a noninducible and an inducible pathway, the latter forming 4-OH-CP. In the final enzyme model, CP affects the amount of enzymes by increasing the enzyme production rate. CP concentrations decreased during the infusion with no subsequent change in 4-OH-CP concentrations. CP inducible and noninducible clearance were estimated to 1.76 l h-1 (90% C.I. 0.92-2.58) and 1.14 l h-1 (0.31-1.85), respectively. The induction resulted in an approximately doubled CP clearance through the inducible pathway at the end of treatment. The model predicted the enzyme turn-over half-life to be 24 h. CONCLUSIONS The presented mechanism-based enzyme induction model where the pharmacokinetics of the inducer and the enzyme pool counterbalance each other successfully described CP autoinduction. It is reasonable to believe that CP affects its own elimination by increasing the enzyme production rate and thereby increasing the amount of enzyme by which CP is eliminated.
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Affiliation(s)
- M Hassan
- Department of Hematology, Huddinge University Hospital, Huddinge; Department of Medical Laboratory Science and Technology, Division of Clinical Pharmacology, Huddinge University Hospital, Huddinge; Karolinska Pharmacy, Sweden.
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Pan WJ, Hedaya MA. Cocaine and alcohol interactions in the rat: contribution of cocaine metabolites to the pharmacological effects. J Pharm Sci 1999; 88:468-76. [PMID: 10187759 DOI: 10.1021/js980283h] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The pharmacokinetics and pharmacodynamics of cocaine and its three metabolites, benzoylecgonine, norcocaine, and cocaethylene, were investigated in awake, freely moving rats. This work was performed to examine the effect of alcohol coadministration on the metabolic profile of cocaine and to determine the contribution of cocaine metabolites to the pharmacological responses observed after cocaine administration. The plasma and brain extracellular fluid concentration-time profiles were characterized after intravenous (iv) administration of cocaine and the three metabolites in a crossover experimental design. The neurochemical response, measured as the change in dopamine concentration in the nucleus accumbens, and the cardiovascular responses, measured as the change in the mean arterial blood pressure, heart rate, and QRS interval, were monitored simultaneously. Cocaethylene had the highest brain-to-plasma distribution ratio, followed by cocaine, norcocaine, and benzoylecgonine. The estimated total body clearances for cocaine, benzoylecgonine, norcocaine, and cocaethylene were 140 +/- 19, 14.7 +/- 1.2, 130 +/- 19, and 111 +/- 16 mL/min/kg, respectively. Alcohol coadministration increased the formation of norcocaine, decreased the formation of benzoylecgonine, and resulted in the formation of the pharmacologically active metabolite cocaethylene. When cocaine was administered with alcohol, 12.9 +/- 3.1% to 15.3 +/- 2.9% of the cocaine dose was converted to cocaethylene. Benzoylecgonine did not have any central nervous system or cardiovascular activities after iv administration. Compared with cocaine, norcocaine and cocaethylene had more potent and prolonged effects on the neurochemical, heart rate, and QRS interval responses, and were equipotent in increasing the mean arterial blood pressure. These results indicate that changes in the cocaine metabolic profile and the formation of the pharmacologically active metabolite cocaethylene are, at least partially, responsible for the more intense and longer lasting effects reported after using this drug in combination with alcohol.
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Affiliation(s)
- W J Pan
- Pharmacology/Toxicology Graduate Program, Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Pullman, Washington 99164-6510, USA
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Svensson US, Ashton M, Trinh NH, Bertilsson L, Dinh XH, Nguyen VH, Nguyen TN, Nguyen DS, Lykkesfeldt J, Le DC. Artemisinin induces omeprazole metabolism in human beings. Clin Pharmacol Ther 1998; 64:160-7. [PMID: 9728896 DOI: 10.1016/s0009-9236(98)90149-7] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
OBJECTIVE This study investigated whether time-dependent artemisinin pharmacokinetics correlated to CYP3A4 or CYP2C19 activity in vivo. METHODS Artemisinin (two oral doses per day of 250 mg) was given to nine healthy Vietnamese subjects for 7 days (day 1 to day 7). Single 20 mg doses of omeprazole were given orally on day -7, day 1, and day 7. Single doses of artemisinin and omeprazole were given in combination on day 14 after a 6-day washout period. The pharmacokinetics of artemisinin, omeprazole, hydroxyomeprazole, and omeprazole sulfone were evaluated on days -7, 1, 7, and 14. On the same days urine was collected for the determination of 6beta-hydroxycortisol and cortisol excretion. RESULTS Areas under plasma concentration-time curves (AUC) for artemisinin and omeprazole decreased on day 7 to 20% (95% confidence intervals, 13%, 28%) and 35% (25%, 46%), respectively, compared with values on day 1. AUC ratios for hydroxyomeprazole/omeprazole increased 2.2-fold (1.7, 2.7) on day 7 compared with values on day 1. All values were normalized at day 14. There were no significant changes in the omeprazole sulfone/omeprazole ratio or in the 6beta-hydroxycortisol/cortisol ratio between the study days. In one subject found to have poor CYP2C19 metabolization, the elimination of omeprazole increased after artemisinin exposure, with no change in the hydroxyomeprazole/omeprazole AUC ratio. CONCLUSION Artemisinin did not alter CYP3A4 activity, whereas an increase in CYP2C19 activity was observed. The increased elimination of omeprazole in both poor and extensive CYP2C19 metabolizers suggests artemisinin induces both CYP2C19 and another enzyme.
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Affiliation(s)
- U S Svensson
- Department of Pharmacy, Uppsala University, Sweden
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Riad LE, Sawchuk RJ. A partial area difference analysis for estimating elimination rate constants and distribution volumes of metabolites. J Pharm Sci 1998; 87:769-73. [PMID: 9607957 DOI: 10.1021/js970321h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The true elimination rate constant of a metabolite is calculated using a partial area difference analysis. A linear pharmacokinetic model which describes clearances of parent and metabolite is developed. The model makes no restrictions on the route of administration of the parent but requires time-invariant kinetics for both parent and metabolite. Carbamazepine (CBZ), an antiepileptic, is metabolized to the 10,11-epoxide (CBZE), which is further hydrated to the trans-dihydrodiol (CBZD). Plasma data of the metabolites after a 200-mg single oral dose of Tegretol chewable tablets is used to demonstrate the applicability of the method. Elimination rate constants calculated using partial area analysis are 0.087 +/- 0.015 (h-1) and 0.056 +/- 0.014 (h-1) for CBZE and CBZD, respectively. These correspond to an average half-life of 8.0 h for CBZE and 12.4 h for CBZD, which suggest elimination-rate-limited disappearance of CBZD. The elimination rate constants for CBZE and CBZD calculated using partial areas are comparable to those in the literature determined after oral administration of CBZE. Volumes of distribution of CBZE and CBZD are also estimated to be 0.57 +/- 0.11 L/kg and 0.76 +/- 0.24 L/kg, respectively. The higher values observed with CBZD volumes of distribution are attributed to the higher plasma free fraction of the diol relative to CBZE.
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Affiliation(s)
- L E Riad
- Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Weaver-Densford Hall, 308 Harvard St. S.E., Minneapolis, Minnesota 55455-0343, USA
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El-Zein H, Riad L, El-Bary AA. Enhancement of carbamazepine dissolution: in vitro and in vivo evaluation. Int J Pharm 1998. [DOI: 10.1016/s0378-5173(98)00093-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Dickinson PA, Taylor G. Route dependent pulmonary first-pass metabolism of a series of biphenylacetic acid esters in rats. Eur J Pharm Sci 1998; 6:11-8. [PMID: 16256703 DOI: 10.1016/s0928-0987(97)00062-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/1996] [Accepted: 03/28/1997] [Indexed: 11/15/2022]
Abstract
The influence of route of administration of a series of biphenylacetic acid aliphatic esters on their pulmonary first-pass metabolism in rats was investigated. The results were compared with in vitro data and with the physicochemical properties of the esters. Pre- and post-absorptive first-pass metabolism was assessed by comparing area under blood concentration-time curves after intra-arterial administration of the esters with those seen after intravenous (to assess post-absorptive) and intratracheal (to assess pre-absorptive) administration. The extent of pulmonary metabolism was dependent on the route of administration. For all the esters studied there was insignificant post-absorptive first-pass extraction, however there was a large pre-absorptive first-pass extraction (greater than 80%). Enzyme kinetics derived in vitro using the 'well-stirred' model (Dickinson and Taylor, 1995. Int. J. Pharm. 116, 231-236) predicted the extent of post-absorptive but not the pre-absorptive, first-pass metabolism.
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Affiliation(s)
- P A Dickinson
- Welsh School of Pharmacy, UWC, Cathays Park, Cardiff CF1 3XF, UK.
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Srinivas N, Kaul S. Pharmacokinetics of a nootropic agent, BMY-21502, and its metabolites in beagle dogs. Eur J Drug Metab Pharmacokinet 1998; 23:61-5. [PMID: 9625274 DOI: 10.1007/bf03189828] [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: 02/07/2023]
Abstract
A preliminary investigation into the pharmacokinetics of BMY-21502, a nootropic agent, and two of its metabolites, BMY-42191 and BMY-40440, was performed in 4 beagle dogs. Following oral dosing of a solution of BMY-21502 (0.61 mmoles), plasma samples were obtained for 24 h and analyzed for the three analytes by a validated HPLC assay. BMY-21502 was rapidly absorbed (Tmax = 0.5 +/- 0.3 h), followed by a rapid decline of the plasma levels (T1/2 = 0.95 +/- 0.1 h). The hydroxy metabolite, BMY-42191, was rapidly formed and the peak concentrations in plasma were obtained by 2.88 +/- 0.2 h. On the contrary, there was a considerable delay in the peaking of the ketone metabolite, BMY-40440 (Tmax = 6 h). The T1/2 values for BMY-40440 (5.58 +/- 0.5 h) were longer than those for BMY-42191 (4.28 +/- 1.2 h). Comparison of AUC values for BMY-42191 (326.43 +/- 63.3 h x microM) with those of BMY-40440 (67.52 +/- 8.4 h x microM) or BMY-21502 (69.35 +/- 7.3 h x microM) indicated that BMY-42191 was the major circulating species in dog plasma. In conclusion, the preliminary data indicate that the metabolism of BMY-21502 is complex and may encompass hydroxy-ketone metabolic interconversions, as reported for other xenobiotics.
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Affiliation(s)
- N Srinivas
- Metabolism and Pharmacokinetics, Pharmaceutical Research Institute, Bristol-Myers Squibb Company, Princeton, New Jersey 08543-4000, USA
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Mellick GD, Anissimov YG, Bracken AJ, Roberts MS. Metabolite mean transit times in the liver as predicted by various models of hepatic elimination. JOURNAL OF PHARMACOKINETICS AND BIOPHARMACEUTICS 1997; 25:477-505. [PMID: 9561490 DOI: 10.1023/a:1025797126763] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Predicted area under curve (AUC), mean transit time (MTT) and normalized variance (CV2) data have been compared for parent compound and generated metabolite following an impulse input into the liver. Models studied were the well-stirred (tank) model, tube model, a distributed tube model, dispersion model (Danckwerts and mixed boundary conditions) and tanks-in-series model. It is well known that discrimination between models for a parent solute is greatest when the parent solute is highly extracted by the liver. With the metabolite, greatest model differences for MTT and CV2 occur when parent solute is poorly extracted. In all cases the predictions of the distributed tube, dispersion, and tanks-in-series models are between the predictions of the tank and tube models. The dispersion model with mixed boundary conditions yields identical predictions to those for the distributed tube model (assuming an inverse gaussian distribution of tube transit times). The dispersion model with Danckwerts boundary conditions and the tanks-in series models give similar predictions to the dispersion (mixed boundary conditions) and the distributed tube. The normalized variance for parent compound is dependent upon hepatocyte permeability only within a distinct range of permeability values. This range is similar for each model but the order of magnitude predicted for normalized variance is model dependent. Only for a one-compartment system is the MTT for generated metabolite equal to the sum of MTTs for the parent compound and preformed metabolite administered as parent.
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Affiliation(s)
- G D Mellick
- Department of Medicine, University of Queensland, Princess Alexandra Hospital, Brisbane, Australia
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Denaro CP, Wilson M, Jacob P, Benowitz NL. Validation of urine caffeine metabolite ratios with use of stable isotope-labeled caffeine clearance. Clin Pharmacol Ther 1996; 59:284-96. [PMID: 8653991 DOI: 10.1016/s0009-9236(96)80006-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVE A number of caffeine metabolite ratios have been proposed to measure CYP1A2 activity in vivo. The data to validate these ratios are scanty. The objective of this study was to validate urine caffeine metabolite ratios versus stable isotope-labeled caffeine clearance under different caffeine dosing conditions. STUDY DESIGN Two experiments, one with nine nonsmoking subjects and the other with 12 cigarette smokers, were performed. We explored the relationship between caffeine clearance, measured by means of intravenous infusions of stable isotope-labeled caffeine, and a number of caffeine metabolite ratios during administration of different single or multiple doses of caffeine to smokers and nonsmokers on three different occasions over a 2-week period, using different durations of urine collections, including spot urines. The stable isotope technique allowed simultaneous oral dosing of caffeine and measurement of caffeine metabolite ratios and caffeine clearance, the latter reflecting CYP1A2 activity. RESULTS The caffeine metabolite ratio of AAMU + 1U +1X/17U (5-acetylamino-6-amino-3-methyluracil + 1-methyluric acid + 1 methylxanthine/1,7-dimethyluric acid) maintained a significant correlation with caffeine clearance for all the above conditions (gamma2 range, 0.4 to 0.9) except for dose. With high doses of caffeine (12 mg/kg), a significant relationship was not observed. AAMU + 1U + 1X/17U also correlated with the formation clearance of paraxanthine (gamma2 = 0.6, p = 0.002). Other reported caffeine metabolite ratios did not display the same robust correlation with caffeine clearance under all these different conditions. CONCLUSIONS We conclude that AAMU+1U+1X/17U measured from a single spot urine collection is a valid measure of CYP1A2 activity except at very high levels of caffeine dosing. The validity of the other proposed caffeine metabolite ratios is questionable.
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Affiliation(s)
- C P Denaro
- Division of Clinical Pharmacology and Experimental Therapeutics, Medical Service, San Francisco General Hospital Medical Center, California 94110, USA
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Rydberg T, Jönsson A, Melander A. Comparison of the kinetics of glyburide and its active metabolites in humans. J Clin Pharm Ther 1995; 20:283-95. [PMID: 8576296 DOI: 10.1111/j.1365-2710.1995.tb00664.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The pharmacokinetics of glyburide (Gb) and its active metabolites, 4-trans-hydroxyglibenclamide (M1) and 3-cis-hydroxyglibenclamide (M2), were compared in eight healthy subjects. After an overnight fast, each subject received a 3.5-mg single dose of Gb, M1 or M2 intravenously in random cross-over order. For comparison, a 3.5-mg oral dose of micronized formulation of Gb was also given in a test. The subjects continued to fast until standard meals were given at 0.5 and 5.5 h after each dose. Serum samples and urine fractions were collected for 10 h. Serum concentrations of Gb, M1 and M2, and urine concentrations of M1 and M2 were determined by a selective and sensitive liquid chromatographic method. The two metabolites had very similar pharmacokinetic profiles, except for volume of distribution and renal clearance. Estimated mean volume of distribution, total and renal clearance of M1 and M2 were 20.8 +/- 8.4 litres, 11.9 +/- 1.7 litres/h, 13.5 +/- 3.7 litres/h and 15.5 +/- 5.5 litres, 10.4 +/- 1.3 litres/h, 8.6 +/- 1.6 litres/h, respectively. Estimates of the volume of distribution and total clearance were significantly higher than those of Gb, which were 7.44 +/- 1.53 litres, 4.42 +/- 0.56 litres/h intravenously and 9.32 +/- 2.79 litres, 4.09 +/- 0.45 litres/h orally. There was no significant difference in total metabolite urine recovery between intravenous or oral administration of Gb, suggesting almost complete oral bioavailability of the micronized glibenclamide formulation.
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Affiliation(s)
- T Rydberg
- Hospital Pharmacy, Central Hospital, Kristianstad, Sweden
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Kim RB, O'Shea D. Interindividual variability of chlorzoxazone 6-hydroxylation in men and women and its relationship to CYP2E1 genetic polymorphisms. Clin Pharmacol Ther 1995; 57:645-55. [PMID: 7781264 DOI: 10.1016/0009-9236(95)90227-9] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Chlorzoxazone 6-hydroxylation is mediated by CYP2E1, and its measurement provides an in vivo probe of the enzyme's activity. To determine the population distribution of such activity, the disposition of chlorzoxazone and its 6-hydroxy metabolite was determined after oral administration to 70 white subjects (40 men and 30 women) residing in middle Tennessee. Both oral (330 +/- 111 ml.min-1, mean +/- SD) and fractional (213 +/- 86 ml.min-1) clearances varied fourfold to fivefold within the population and were unimodally distributed in a visually normal fashion. Clearance values were one-third greater in men than in women, but such differences were less striking after normalization according to body weight. Attempts to develop a single-time-point measure of 6-hydroxylating ability on the basis of plasma levels or urinary excretion of chlorzoxazone or its metabolite were unsuccessful. Genetic polymorphisms (Pst I and Rsa I restriction fragment length polymorphisms) in the 5'-flanking region of CYP2E1 deoxyribonucleic acid obtained from peripheral leukocytes were not associated with differences in the disposition of chlorzoxazone. Similarly, no major effects on 6-hydroxylation were associated with mutations in intron 6 associated with a Dra I restriction fragment length polymorphism. The interindividual variability in CYP2E1 activity as measured in vivo in healthy subjects appears to be considerably less than that expected based on in vitro studies. Whether such variability is associated with individual susceptibility to CYP2E1-mediated toxicity remains to be determined.
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Affiliation(s)
- R B Kim
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232-6600, USA
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Sams R, Gerken DF, Ashcraft SM. Pharmacokinetics of ketoprofen after multiple intravenous doses to mares. J Vet Pharmacol Ther 1995; 18:108-16. [PMID: 7629924 DOI: 10.1111/j.1365-2885.1995.tb00563.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The pharmacokinetics and urinary excretion of ketoprofen in six healthy mares after the first and last of five daily intravenous doses of 2.2 mg of ketoprofen per kg body weight were investigated using a high-performance liquid chromatographic (HPLC) method for determining plasma and urinary ketoprofen concentrations. Plasma ketoprofen concentrations declined triexponentially after each dose with no significant differences in plasma concentrations or pharmacokinetic parameter values between the first and last doses. The harmonic mean of the terminal elimination half-life of ketoprofen after the first and last dose was 98.2 and 78.0 min, respectively. The median values of the total plasma clearance and the renal clearance after the first dose were 4.81 and 1.93 mL/min/kg, respectively. Total plasma clearance was attributed to renal excretion of ketoprofen and metabolism of ketoprofen to a base-labile conjugate which was also excreted in the urine. Renal clearance of ketoprofen was attributed to renal tubular secretion since renal clearance was greater than filtration clearance. Urinary recovery of ketoprofen during the first 420 min after the first dose accounted for 26.4% of the dose as unconjugated ketoprofen and 29.8% of the dose as a base-labile conjugate of ketoprofen. Total urinary recovery of ketoprofen as unchanged ketoprofen and from base-labile conjugate represented 56.2% of the dose. Plasma protein binding of ketoprofen was extensive; the mean plasma protein binding of ketoprofen was 92.8% (SD 3.0%) at 500 ng/mL and 91.6% (SD 0.60%) at 10.0 micrograms/mL.
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Affiliation(s)
- R Sams
- Analytical Toxicology Laboratory, College of Veterinary Medicine, Ohio State University, Columbus 43210, USA
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Xu ZX, Sun YN, DuBois DC, Almon RR, Jusko WJ. Third-generation model for corticosteroid pharmacodynamics: roles of glucocorticoid receptor mRNA and tyrosine aminotransferase mRNA in rat liver. JOURNAL OF PHARMACOKINETICS AND BIOPHARMACEUTICS 1995; 23:163-81. [PMID: 8719235 DOI: 10.1007/bf02354270] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A third-generation pharmacokinetic/pharmacodynamic model was proposed for receptor/gene-mediated corticosteroid effects. The roles of the messenger RNA (mRNA) for the glucocorticoid receptor (GR) in hepatic GR down-regulation and the mRNA for hepatic tyrosine aminotransferase (TAT) induction by methylprednisolone (MPL) were examined. Male adrenalectomized Wistar rats received 50 mg/kg MPL iv. Blood and liver samples were collected at various time points for a period of 18 hr. Plasma concentrations of MPL, free hepatic cytosolic GR densities, GR mRNA, TAT mRNA, and TAT activities in liver were determined. Plasma MPL profile was biexponential with a terminal t1/2 of 0.57 hr. Free hepatic GR density rapidly disappeared from cytoplasm after the MPL dose and then slowly returned to about 60% of starting level after 16 hr. Meanwhile, GR mRNA level fell to 45% of baseline within 2 hr postdosing, and remained at that level for at least 18 hr. The GR down-regulation of GR mRNA and protein turnover rate were modeled. The TAT mRNA began to increase at about 2 hr, reached a maximum at about 5 hr, and declined to baseline by 14 hr. TAT induction followed a similar pattern, except the induction was delayed about 0.5 hr. Pharmacodynamic parameters were obtained by fitting seven differential equations in a piecewise fashion. The cascade of corticosteroid steps were modeled by a series of inductions for steroid-receptor-DNA complex, two intermediate transit compartments, TAT mRNA, and TAT activity. Results indicate that GR mRNA and TAT mRNA are major controlling factors for the receptor/gene-mediated effects of corticosteroids.
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Affiliation(s)
- Z X Xu
- Department of Pharmaceutics, State University of New York at Buffalo 14260, USA
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