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Minegishi G, Kazuki Y, Yamasaki Y, Okuya F, Akita H, Oshimura M, Kobayashi K. Comparison of the hepatic metabolism of triazolam in wild-type andCyp3a-knockout mice for understanding CYP3A-mediated metabolism inCYP3A-humanised mice in vivo. Xenobiotica 2019; 49:1303-1310. [DOI: 10.1080/00498254.2018.1560516] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Genki Minegishi
- Laboratory of DDS design and Drug Disposition, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba, Japan
| | - Yasuhiro Kazuki
- Chromosome Engineering Research Center, Tottori University, Tottori, Japan
- Department of Biomedical Science, Institute of Regenerative Medicine and Biofunction, Graduate School of Medical Science, Tottori University, Tottori, Japan
| | - Yuki Yamasaki
- Laboratory of DDS design and Drug Disposition, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba, Japan
| | - Fuka Okuya
- Laboratory of DDS design and Drug Disposition, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba, Japan
| | - Hidetaka Akita
- Laboratory of DDS design and Drug Disposition, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba, Japan
| | - Mitsuo Oshimura
- Chromosome Engineering Research Center, Tottori University, Tottori, Japan
| | - Kaoru Kobayashi
- Laboratory of DDS design and Drug Disposition, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba, Japan
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2
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Current strategies to streamline pharmacotherapy for older adults. Eur J Pharm Sci 2018; 111:432-442. [DOI: 10.1016/j.ejps.2017.10.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 10/09/2017] [Accepted: 10/10/2017] [Indexed: 01/08/2023]
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3
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Gentile G, Cipolla F, Capi M, Simmaco M, Lionetto L, Borro M. Precise medical decision making in geriatric anti-depressant therapy. EXPERT REVIEW OF PRECISION MEDICINE AND DRUG DEVELOPMENT 2016. [DOI: 10.1080/23808993.2016.1199951] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Giovanna Gentile
- Department of Neurosciences, Mental Health and Sensory Organs, Sapienza University of Rome, Rome, Italy
| | - Fabiola Cipolla
- Department of Neurosciences, Mental Health and Sensory Organs, Sapienza University of Rome, Rome, Italy
| | - Matilde Capi
- Department of Neurosciences, Mental Health and Sensory Organs, Sapienza University of Rome, Rome, Italy
| | - Maurizio Simmaco
- Department of Neurosciences, Mental Health and Sensory Organs, Sapienza University of Rome, Rome, Italy
| | - Luana Lionetto
- Advanced Molecular Diagnostics, IDI, Istituto Dermopatico dell’Immacolata-IRCCS, Rome, Italy
| | - Marina Borro
- Department of Neurosciences, Mental Health and Sensory Organs, Sapienza University of Rome, Rome, Italy
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Gupta M, Kovar A, Meibohm B. The Clinical Pharmacokinetics of Phosphodiesterase-5 Inhibitors for Erectile Dysfunction. J Clin Pharmacol 2013; 45:987-1003. [PMID: 16100293 DOI: 10.1177/0091270005276847] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Differences in the clinical pharmacology of the 3 currently available oral phosphodiesterase-5 (PDE5) inhibitors, sildenafil, vardenafil, and tadalafil, are largely determined by their clinical pharmacokinetics as well as their PDE inhibitory activity profile. This review comparatively discusses the major characteristics of the pharmacokinetic profile of all 3 PDE5 inhibitors, including bioavailability and rate of absorption, Biopharmaceutical Classification System categorization, elimination mechanisms, and metabolic profile including active metabolites, as well as the drug-drug interaction potential and modification of pharmacokinetic properties under selected physiologic and pathophysiologic conditions. The review is aimed at providing comparative clinical pharmacology data to allow for scientifically rational, evidence-based prescribing and dosing decisions regarding the clinical use of these medications for the treatment of erectile dysfunction.
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Affiliation(s)
- Manish Gupta
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, 874 Union Avenue, Suite 5p, Memphis, TN 38163, USA
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5
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Abstract
The elderly frequently have changes in pharmacokinetics, sensitivity to medications, homeostatic reserve (ability to tolerate physiological challenges), exposure to multiple medications, and adherence. All of these age-associated factors can potentially influence total exposure to medication, adverse effects, and subsequent treatment outcome. Most clinical trials are performed with healthy, younger adults. Extrapolating the results of these trials to the elderly may be inappropriate, particularly for the antidepressant treatment of depression. The authors review these age-associated differences and discuss their implications for antidepressant use in older adults.
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Affiliation(s)
- Francis E Lotrich
- Western Psychiatric Institute and Clinic, University of Pittsburgh Medical Center, 3811 O'Hara Street, Pittsburgh, PA 15213, USA.
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6
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Guest EJ, Rowland-Yeo K, Rostami-Hodjegan A, Tucker GT, Houston JB, Galetin A. Assessment of algorithms for predicting drug-drug interactions via inhibition mechanisms: comparison of dynamic and static models. Br J Clin Pharmacol 2011; 71:72-87. [PMID: 21143503 DOI: 10.1111/j.1365-2125.2010.03799.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT The prediction of drug-drug interactions (DDIs) from in vitro data usually utilizes an average dosing interval estimate of inhibitor concentration in an equation-based static model. Simcyp®, a population-based ADME simulator, is becoming widely used for the prediction of DDIs and has the ability to incorporate the time-course of inhibitor concentration and hence generate a temporal profile of the inhibition process within a dynamic model. WHAT THIS PAPER ADDS Prediction of DDIs for 35 clinical studies incorporating a representative range of drug-drug interactions, with multiple studies across different inhibitors and victim drugs. Assessment of whether the inclusion of the time course of inhibition in the dynamic model improves prediction in comparison with the static model. Investigation of the impact of different inhibitor and victim drug parameters on DDI prediction accuracy including dosing time and the inclusion of active metabolites. Assessment of ability of the dynamic model to predict inter-individual variability in the DDI magnitude. AIMS Static and dynamic models (incorporating the time course of the inhibitor) were assessed for their ability to predict drug-drug interactions (DDIs) using a population-based ADME simulator (Simcyp®V8). The impact of active metabolites, dosing time and the ability to predict inter-individual variability in DDI magnitude were investigated using the dynamic model. METHODS Thirty-five in vivo DDIs involving azole inhibitors and benzodiazepines were predicted using the static and dynamic model; both models were employed within Simcyp for consistency in parameters. Simulations comprised of 10 trials with matching population demographics and dosage regimen to the in vivo studies. Predictive utility of the static and dynamic model was assessed relative to the inhibitor or victim drug investigated. RESULTS Use of the dynamic and static models resulted in comparable prediction success, with 71 and 77% of DDIs predicted within two-fold, respectively. Over 40% of strong DDIs (>five-fold AUC increase) were under-predicted by both models. Incorporation of the itraconazole metabolite into the dynamic model resulted in increased prediction accuracy of strong DDIs (80% within two-fold). Bias and imprecision in prediction of triazolam DDIs were higher in comparison with midazolam and alprazolam; >50% of triazolam DDIs were under-predicted regardless of the model used. Predicted inter-individual variability in the AUC ratio (coefficient of variation of 45%) was consistent with the observed variability (50%). CONCLUSIONS High prediction accuracy was observed using both the Simcyp dynamic and static models. The differences observed with the dose staggering and the incorporation of active metabolite highlight the importance of these variables in DDI prediction.
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Affiliation(s)
- Eleanor J Guest
- School of Pharmacy and Pharmaceutical Sciences, University of Manchester, Oxford Road, Manchester, UK
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7
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Bolling BW, Court MH, Blumberg JB, Chen CYO. The kinetic basis for age-associated changes in quercetin and genistein glucuronidation by rat liver microsomes. J Nutr Biochem 2009; 21:498-503. [PMID: 19446449 DOI: 10.1016/j.jnutbio.2009.02.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Revised: 01/22/2009] [Accepted: 02/09/2009] [Indexed: 10/20/2022]
Abstract
The dietary bioavailability of the isoflavone genistein is decreased in older rats compared to young adults. Since flavonoids are metabolized extensively by the UDP-glucuronosyltransferases (UGTs), we hypothesized that UGT flavonoid conjugating activity changes with age. The effect of age on flavonoid glucuronidation was determined using hepatic microsomes from male F344 rats. Kinetic models of UGT activity toward the flavonol quercetin and the isoflavone genistein were established using pooled hepatic microsomal fractions of rats at different ages, and glucuronidation rates were determined using individual samples. Intrinsic clearance (V(max)/K(m)) values in 4-, 18- and 28-month-old rats were 0.100, 0.078 and 0.087 ml/min/mg for quercetin-7-O-glucuronide; 0.138, 0.133 and 0.088 for quercetin-3'-O-glucuronide; and 0.075, 0.077 and 0.057 for quercetin-4'-O-glucuronide, respectively. While there were no differences in formation rates of total quercetin glucuronides in individual samples, the production of the primary metabolite, quercetin-7-O-glucuronide, at 30 microM quercetin concentration was increased from 3.4 and 3.1 nmol/min/mg at 4 and 18 months to 3.8 nmol/min/mg at 28 months, while quercetin-3'-O-glucuronide formation at 28 months declined by a similar degree (P<or=.05). At 30 and 300 microM quercetin concentration, the rate of quercetin-4'-O-glucuronide formation peaked at 18 months at 0.9 nmol/min/mg. Intrinsic clearance values of genistein 7-O-glucuronide increased with age, in contrast to quercetin glucuronidation. Thus, the capacity for flavonoid glucuronidation by rat liver microsomes is dependent on age, UGT isoenzymes and flavonoid structure.
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Affiliation(s)
- Bradley W Bolling
- Antioxidants Research Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA
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8
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Shang H, Yang J, Liu Y, Wei H. Tissue distribution of CYP3A29 mRNA expression in Bama miniature pig by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Xenobiotica 2009; 39:423-9. [DOI: 10.1080/00498250902825363] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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9
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Kramer MA, Tracy TS. Studying cytochrome P450 kinetics in drug metabolism. Expert Opin Drug Metab Toxicol 2008; 4:591-603. [PMID: 18484917 DOI: 10.1517/17425255.4.5.591] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
BACKGROUND Determination of cytochrome P450 enzyme-mediated kinetics in vitro can be useful for predicting drug dosing and clearance in humans. Expressed P450s, human liver microsomes, human hepatocytes (both fresh and cryopreserved), and human liver slices are used to estimate K(m) and V(max) values for determination of intrinsic clearance of the drug for scale-up to predict in vivo clearance. OBJECTIVE To describe the advantages and disadvantages of the various in vitro systems used to estimate kinetic parameters for disposition of drugs and the various kinetic profiles that can be observed. METHODS A review of the literature was conducted to evaluate the utility of the various in vitro preparations, the methods for determining kinetic parameters and the types of kinetic profiles that may be observed. RESULTS/CONCLUSIONS The choice of in vitro system for determining kinetic parameters will depend on the objective of the studies, as each system has advantages and disadvantages. Kinetic parameter determinations must be carefully assessed to assure that the correct kinetic model is applied and the most accurate kinetic parameters are determined.
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Affiliation(s)
- Melissa A Kramer
- University of Minnesota, College of Pharmacy, Department of Experimental and Clinical Pharmacology, 7-115B Weaver-Densford Hall, 308 Harvard Street SE, Minneapolis, MN 55455, USA
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Gan L, von Moltke LL, Trepanier LA, Harmatz JS, Greenblatt DJ, Court MH. Role of NADPH-cytochrome P450 reductase and cytochrome-b5/NADH-b5 reductase in variability of CYP3A activity in human liver microsomes. Drug Metab Dispos 2008; 37:90-6. [PMID: 18838505 DOI: 10.1124/dmd.108.023424] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
NADPH-cytochrome P450 reductase (CPR) and cytochrome-b(5) (b(5)) together with NADH-b(5) reductase (b(5)R) play important roles in cytochrome P450 3A-mediated drug metabolism via electron transfer. However, it is not clear whether variability in expression of these accessory proteins contributes to the known interindividual variability in CYP3A activity. CPR and b(5) were measured in human liver microsomes (HLMs) by spectrophotometry and immunoblotting. HLMs from elderly (>or=46 years) male donors (n=11) averaged 27% (P=0.034) and 41% (P=0.011) lower CPR levels than young (<or=45 years) male donors (n=21) for spectrophotometric and immunoblot values, respectively. Similarly, HLMs from elderly male donors averaged 43% (P=0.034) and 47% (P=0.011) lower b(5) levels than young male donors for spectrophotometric and immunoblot values, respectively. alpha-Lipoic acid and 6-propyl-2-thiouracil were evaluated for selectivity of inhibition of CPR and b(5)R activities, respectively, using recombinant enzymes and HLMs, as well as for effects on CYP3A-mediated triazolam hydroxylation in HLMs with either NADH or beta-NADPH. The results indicate that both compounds are relatively nonselective inhibitors of CPR and b(5)R activities. Finally, we used multivariate regression analysis and showed that variability in CPR or b(5) expression between HLMs does not contribute significantly to variability in CYP3A-mediated midazolam hydroxylation. Consequently, while aging is associated with decreased CPR and b(5) expression in human livers, this effect does not contribute to CYP3A variability.
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Affiliation(s)
- Lu Gan
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, 136 Harrison Avenue, Boston, Massachusetts 02111, USA
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11
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Schwartz JB. The Current State of Knowledge on Age, Sex, and Their Interactions on Clinical Pharmacology. Clin Pharmacol Ther 2007; 82:87-96. [PMID: 17495875 DOI: 10.1038/sj.clpt.6100226] [Citation(s) in RCA: 170] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Pharmacokinetic and pharmacodynamic changes occur with increasing age. Sex differences in pharmacokinetics and pharmacodynamics exist and persist at older age. The issue for the clinician is how to best treat the older patient with currently available knowledge. This communication highlights age- and sex-related differences in pharmacokinetics that should influence clinical practice and prescribing guidelines to optimize clinical responses. The most compelling data for sex-specific medication dosing guidelines for older patients are related to volume of distribution differences, or size differences, between the sexes and to differences in glomerular filtration rates.
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Affiliation(s)
- J B Schwartz
- Jewish Home of San Francisco, University of California San Francisco, San Francisco, California, USA.
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12
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Astobieta Odriozola A, Ibarluzea González G, Pereira Arias J, Gallego Sánchez J, Gamarra Quintanilla M, Camargo Ibargaray I. La farmacocinética/farmacodinámica de los iPDE5. ¿Clínicamente significativos? La farmacocinética clínica de los inhibidores de la fosfodiesterasa tipo 5 en disfunción eréctil. Rev Int Androl 2007. [DOI: 10.1016/s1698-031x(07)74034-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Hariparsad N, Sane RS, Strom SC, Desai PB. In vitro methods in human drug biotransformation research: implications for cancer chemotherapy. Toxicol In Vitro 2006; 20:135-53. [PMID: 16359840 DOI: 10.1016/j.tiv.2005.06.049] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2005] [Revised: 05/01/2005] [Accepted: 06/01/2005] [Indexed: 11/28/2022]
Abstract
Anticancer drugs have a complex pharmacological and toxicological profile with a narrow therapeutic index. It is therefore critical to understand the factors that contribute to the marked intersubject variability in the pharmacokinetics and pharmacodynamics often observed with anticancer compounds. Since hepatic and extra-hepatic drug metabolism represents a major drug disposition pathway, extensive efforts are made to thoroughly investigate metabolism of anticancer compounds during the pre-clinical and clinical development phases as well as to address issues encountered during the clinical use of an approved drug. In recent years there has been a significant paradigm shift in pre-clinical/non-clinical drug metabolism studies. Most importantly, this has included a reduced reliance on animal models and increased use of human tissues (i.e. human liver microsomes and other cellular fractions, primary culture of human hepatocytes, cDNA expressed human-specific enzymes and cell-based reporter assays). Typically, experiments are performed using these tools to identify the phase I and/or phase II enzymes involved in metabolism of the drug/investigational agent and for metabolic fingerprinting. Additionally, issues pertaining to the rate, extent and mechanism(s) of the inhibition or induction of the metabolic pathways are also investigated. These studies provide important clues about various aspects of the disposition of a therapeutic agent including first-pass metabolism, elimination half-life, overall bioavailability and the potential for drug-drug interactions. The methodologies used for in vitro assessment of drug metabolism and their applications to drug development and clinical therapeutics with special emphasis on anticancer drugs are reviewed in this manuscript.
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Affiliation(s)
- N Hariparsad
- College of Pharmacy, University of Cincinnati Medical Center, Cincinnati, OH 45267, USA
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14
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Ekins S. Systems-ADME/Tox: resources and network approaches. J Pharmacol Toxicol Methods 2005; 53:38-66. [PMID: 16054403 DOI: 10.1016/j.vascn.2005.05.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2005] [Accepted: 05/23/2005] [Indexed: 01/11/2023]
Abstract
The increasing cost of drug development is partially due to our failure to identify undesirable compounds at an early enough stage of development. The application of higher throughput screening methods have resulted in the generation of very large datasets from cells in vitro or from in vivo experiments following the treatment with drugs or known toxins. In recent years the development of systems biology, databases and pathway software has enabled the analysis of the high-throughput data in the context of the whole cell. One of the latest technology paradigms to be applied alongside the existing in vitro and computational models for absorption, distribution, metabolism, excretion and toxicology (ADME/Tox) involves the integration of complex multidimensional datasets, termed toxicogenomics. The goal is to provide a more complete understanding of the effects a molecule might have on the entire biological system. However, due to the sheer complexity of this data it may be necessary to apply one or more different types of computational approaches that have as yet not been fully utilized in this field. The present review describes the data generated currently and introduces computational approaches as a component of ADME/Tox. These methods include network algorithms and manually curated databases of interactions that have been separately classified under systems biology methods. The integration of these disparate tools will result in systems-ADME/Tox and it is important to understand exactly what data resources and technologies are available and applicable. Examples of networks derived with important drug transporters and drug metabolizing enzymes are provided to demonstrate the network technologies.
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Affiliation(s)
- Sean Ekins
- GeneGo, 500 Renaissance Drive, Suite 106, St. Joseph, MI 49085, USA.
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Cotreau MM, von Moltke LL, Greenblatt DJ. The influence of age and sex on the clearance of cytochrome P450 3A substrates. Clin Pharmacokinet 2005; 44:33-60. [PMID: 15634031 DOI: 10.2165/00003088-200544010-00002] [Citation(s) in RCA: 202] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cytochrome P450s (CYPs) are an important family of enzymes in the metabolism of many therapeutic agents and endogenous metabolic reactions. The CYP3A subfamily is especially prominent in these metabolic activities. This review article focuses on how the factors of age and sex may influence the in vivo activity of human CYP3A. The functional activity of CYP3A varies based on issues such as interaction with one or more substrates and between individuals and/or localisation. For CYP3A substrates, intrinsic clearance is the component of total clearance that is contributed by the enzymes. Depending on the route of administration and the contribution of hepatic blood flow to overall clearance, sensitivities to changes in CYP3A activities may differ. Additionally, age may influence the hepatic blood flow and, in turn, affect CYP3A activity. A review of the literature regarding age influences on the clearance of CYP3A substrates does suggest that age can affect the clearance of certain CYP3A substrates.CYP3A is responsible for a large number of endogenous metabolic reactions involving steroid hormones, and enzyme activity has been reported to be induced and/or inhibited in the presence of some sex steroids. Based on published studies for most CYP3A substrates, sex does not appear to influence clearance; however, with certain substrates significant sex-related differences are found. In such cases, women primarily have higher clearance than men.
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Affiliation(s)
- Monette M Cotreau
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
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Abstract
Relaxation of the upper age limits for solid organ transplantation coupled with improvements in post-transplant survival have resulted in greater numbers of elderly patients receiving immunosuppressant drugs such as tacrolimus. Tacrolimus is a potent agent with a narrow therapeutic window and large inter- and intraindividual pharmacokinetic variability. Numerous physiological changes occur with aging that could potentially affect the pharmacokinetics of tacrolimus and, hence, patient dosage requirements. Tacrolimus is primarily metabolised by cytochrome P450 (CYP) 3A enzymes in the gut wall and liver. It is also a substrate for P-glycoprotein, which counter-transports diffused tacrolimus out of intestinal cells and back into the gut lumen. Age-associated alterations in CYP 3A and P-glycoprotein expression and/or activity, along with liver mass and body composition changes, would be expected to affect the pharmacokinetics of tacrolimus in the elderly. However, interindividual variation in these processes may mask any changes caused by aging. More investigation is needed into the impact aging has on CYP and P-glycoprotein activity and expression. No single-dose, intense blood-sampling study has specifically compared the pharmacokinetics of tacrolimus across different patient age groups. However, five population pharmacokinetic studies, one in kidney, one in bone marrow and three in liver transplant recipients, have investigated age as a co-variate. None found a significant influence for age on tacrolimus bioavailability, volume of distribution or clearance. The number of elderly patients included in each study, however, was not documented and may have been only small. It is likely that inter- and intraindividual pharmacokinetic variability associated with tacrolimus increase in elderly populations. In addition to pharmacokinetic differences, donor organ viability, multiple co-morbidity, polypharmacy and immunological changes need to be considered when using tacrolimus in the elderly. Aging is associated with decreased immunoresponsiveness, a slower body repair process and increased drug adverse effects. Elderly liver and kidney transplant recipients are more likely to develop new-onset diabetes mellitus than younger patients. Elderly transplant recipients exhibit higher mortality from infectious and cardiovascular causes than younger patients but may be less likely to develop acute rejection. Elderly kidney recipients have a higher potential for chronic allograft nephropathy, and a single rejection episode can be more devastating. There is a paucity of information on optimal tacrolimus dosage and target trough concentration in the elderly. The therapeutic window for tacrolimus concentrations may be narrower. Further integrated pharmacokinetic-pharmacodynamic studies of tacrolimus are required. It would appear reasonable, based on current knowledge, to commence tacrolimus at similar doses as those used in younger patients. Maintenance dose requirements over the longer term may be lower in the elderly, but the increased variability in kinetics and the variety of factors that impact on dosage suggest that patient care needs to be based around more frequent monitoring in this age group.
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Affiliation(s)
- Christine E Staatz
- School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia.
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Akahori M, Takatori A, Kawamura S, Itagaki S, Yoshikawa Y. No Regional Differences of Cytochrome P450 Expression in the Liver of Cynomolgus Monkeys (Macaca fascicularis). Exp Anim 2005; 54:131-6. [PMID: 15897621 DOI: 10.1538/expanim.54.131] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Non-human primates are frequently used in toxicological studies the result of which are extrapolated to humans, but background data on drug metabolism ability among monkeys derived from different countries has not been published, especially on the key enzyme, cytochrome P450 (CYP450). We assessed the amounts of hepatic CYP450 obtained from cynomolgus monkeys of different ages and from different countries in this study. There were no regional differences of total P450 content, as well as major CYP450 isozymes (CYP 1A, 2A, 2B, 2C, 2D, 2E1 and 3A4) in cynomolgus monkeys by westernblot analysis. Similarly, there were no significant differences with hybrid cynomolgus monkeys, but variations in individual values were large. As for aging, total P450 contents declined in old cynomolgus monkeys (12-32 years of age). These results indicate the usefulness of basic data of hepatic CYP450 obtained from cynomolgus monkeys of different ages and from different countries.
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Affiliation(s)
- Mizuki Akahori
- Department of Biomedical Science, School of Agricultural and Life Sciences, The University of Tokyo, Japan
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18
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Hariparsad N, Nallani SC, Sane RS, Buckley DJ, Buckley AR, Desai PB. Induction of CYP3A4 by efavirenz in primary human hepatocytes: comparison with rifampin and phenobarbital. J Clin Pharmacol 2004; 44:1273-81. [PMID: 15496645 DOI: 10.1177/0091270004269142] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The antiretroviral agent efavirenz enhances the systemic clearance of coadministered drugs that are cytochrome P450 (CYP) 3A4 substrates. The mechanism of the apparent increase in CYP3A4 activity by efavirenz and the magnitude of change relative to other known inducers are not known. The authors tested the hypothesis that increased enzymatic activity by efavirenz entails CYP3A4 induction and activation of the human pregnane X receptor (hPXR), a key transcriptional regulator of CYP3A4. Employing primary cultures of human hepatocytes, they compared the CYP3A4 inductive effects of efavirenz (1-10 microM) to rifampin (10 microM) and phenobarbital (2 mM). A cell-based reporter assay was employed to assess hPXR activation. The authors observed that efavirenz caused a concentration-dependent CYP3A4 induction and hPXR activation. Based on the CYP3A4 activity assay, the average magnitude of induction by efavirenz (5-10 microM) was approximately 3- to 4-fold. In comparison, phenobarbital (2 mM) and rifampin (10 microM) caused a 5- and 6-fold induction, respectively.
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Affiliation(s)
- Niresh Hariparsad
- College of Pharmacy, University of Cincinnati Medical Center, 3223 Eden Avenue, Mail Location #0004, Cincinnati, OH 45267, USA
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Warrington JS, Greenblatt DJ, von Moltke LL. Age-Related Differences in CYP3A Expression and Activity in the Rat Liver, Intestine, and Kidney. J Pharmacol Exp Ther 2004; 309:720-9. [PMID: 14742746 DOI: 10.1124/jpet.103.061077] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We evaluated the effect of age on CYP3A expression and function in the liver, intestine, and kidney from young (3-4 months), intermediate (13-14 months), and old (25-26 months) male Fischer-344 rats. The biotransformation of triazolam to its primary hydroxylated products, 4-OH-TRZ (triazolam) and alpha-OH-TRZ, was used as a marker of CYP3A activity in rat liver and intestine. Immunoactive CYP3A expression was evaluated by Western blot analysis in the rat intestine, liver, and kidney. Since testosterone and NADPH reductase levels may modulate CYP3A activity, we also examined free plasma testosterone concentrations and NADPH reductase expression in these rats. The effect of age on CYP3A expression was tissue-specific. Although both CYP3A activity and expression were reduced by approximately 50 to 70% in the old livers compared with the young animals, intestinal CYP3A activity and expression did not change significantly with age. The expression of one CYP3A isoform was increased by 1.5-fold in the old kidneys. NADPH reductase expression was reduced by 23 to 36% with age in all tissues; this reached statistical significance only in the liver. Plasma testosterone levels declined by 74% in the old animals. This study suggests that the effect of age on CYP3A expression and function is tissue-specific. In addition, changes in testosterone levels and NADPH reductase expression may contribute to age-related differences in hepatic CYP3A activity.
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Affiliation(s)
- Jill S Warrington
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, MA 02111, USA
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Shiraga T, Niwa T, Ohno Y, Kagayama A. Interindividual Variability in 2-Hydroxylation, 3-Sulfation, and 3-Glucuronidation of Ethynylestradiol in Human Liver. Biol Pharm Bull 2004; 27:1900-6. [PMID: 15577203 DOI: 10.1248/bpb.27.1900] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the current study, we investigated interindividual variability of the 2-hydroxylation, 3-glucuronidation, and 3-sulfation of ethynylestradiol (EE2) using human liver microsomes and cytosol. Km values for the 2-hydroxylation and 3-glucuronidation in pooled liver microsomes and for the 3-sulfation in pooled liver cytosol were 3.34, 23.3, and 2.85 microM, respectively. Vmax/Km (ml/min/g liver) was highest for the 3-sulfation, followed by 2-hydroxylation, suggesting that 3-sulfation is the major metabolic pathway of EE2 in human liver. All further studies were performed at a substrate concentration of 0.1 microM. Microsomal 2-hydroxylation and 3-glucuronidation activities ranged from 0.21 to 5.02 (2.04+/-1.34, mean+/-S.D., n=35) and 0.20 to 4.84 (1.20+/-1.00, n=35) pmol/min/mg protein, respectively. Cytosolic 3-sulfation activity ranged from 4.2 to 24.3 (11.8+/-4.4, n=21) pmol/min/mg protein. All the measured enzyme activities were neither gender-related nor age-dependent, except that 2-hydroxylation was significantly higher in females than in males (p<0.05). The relative contribution of CYP3A to the 2-hydroxylation in liver microsomes was estimated from the degree of inhibition by 1 microM ketoconazole. The degrees of inhibition were between 17.8 and 78.0% (51.6+/-16.0%, n=27). These results indicate that there are large interindividual differences in the enzyme activities towards the respective metabolic pathways of EE2 and the relative contribution of CYP3A to the 2-hydroxylation of EE2 in human liver.
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Affiliation(s)
- Toshifumi Shiraga
- Biopharmaceutical and Pharmacokinetic Research Laboratories, Fujisawa Pharmaceutical Co., Ltd, Osaka, Japan.
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