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Van LM, Hargreaves JA, Lennard MS, Tucker GT, Rostami-Hodjegan A. Inactivation of CYP2D6 by methylenedioxymethamphetamine in different recombinant expression systems. Eur J Pharm Sci 2007; 32:8-16. [PMID: 17574396 DOI: 10.1016/j.ejps.2007.05.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Revised: 04/30/2007] [Accepted: 05/03/2007] [Indexed: 11/19/2022]
Abstract
Recombinantly expressed CYP450 systems (rCYPs) are often used to screen for irreversible/quasi-irreversible enzyme inhibitors during drug development. The concentration- and time-dependent inactivation of CYP2D6 by methylenedioxymethamphetamine (MDMA) was compared in three different rCYP2D6 systems (yeast microsomes, Supersomestrade mark and Bactosomestrade mark) under the conditions of the most commonly used protocols in assessing mechanism-based inactivation (MBI). MDMA (2-20microM) was pre-incubated with enzyme for 0, 2.5 and 5min followed by a five-fold dilution and further incubation with dextromethorpan (DEX) (50microM). The formation of dextrorphan (DOR) from DEX was used as a specific marker of CYP2D6 activity. Concentration- and time-dependent inactivation of CYP2D6 by MDMA was observed with each rCYP system. However, the apparent kinetic parameters for MBI (k(inact), the maximum inactivation rate constant and K(I), the inhibitor concentration associated with half maximal rate of inactivation) were significantly greater (p<0.05) for Bactosomestrade mark (0.95+/-0.33min(-1), 42.9+/-20.1microM) than those found using yeast microsomes (0.28+/-0.04min(-1), 2.86+/-1.18microM) and Supersomestrade mark (0.38+/-0.05min(-1), 3.66+/-0.10microM). After correction for depletion of MDMA during pre-incubation, k(inact) and K(I) values determined using Bactosomestrade mark decreased significantly but remained higher than for the other rCYP systems (p<0.05). Substantial metabolism of DOR after its formation from DEX was also observed using Supersomestrade mark and Bactosomestrade mark. Sub-optimal study design when investigating MBI may compromise the quantitative characterization of inhibitory characteristics using some rCYP systems.
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Affiliation(s)
- Linh M Van
- University of Sheffield, Academic Unit of Clinical Pharmacology, University of Sheffield, Sheffield S10 2JF, UK
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Van LM, Heydari A, Yang J, Hargreaves J, Rowland-Yeo K, Lennard MS, Tucker GT, Rostami-Hodjegan A. The impact of experimental design on assessing mechanism-based inactivation of CYP2D6 by MDMA (Ecstasy). J Psychopharmacol 2006; 20:834-41. [PMID: 16478752 DOI: 10.1177/0269881106062902] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
MDMA (3-4-methylenedioxymethamphetamine, commonly known as Ecstasy) is a potent mechanism-based inhibitor (MBI) of cytochrome P450 2D6 (CYP2D6), causing quasi-irreversible inhibition of the enzyme in vitro. An evaluation of the in vivo implications of this phenomenon depends on the accuracy of the estimates of the parameters that define the inhibition in vitro, namely k(inact) (the maximal inhibition rate) and KI (the inactivation constant). These values are determined in two steps, pre-incubation of the enzyme with the inhibitor (enzyme inactivation), followed by dilution and further incubation to measure residual enzyme activity with a probe substrate. The aim of this study was to assess the impact of different dilutions and probe substrate concentrations on the estimates of k(inact) and KI using recombinantly expressed CYP2D6. Enzyme activity was measured by the conversion of dextromethorphan (DEX) to dextrorphan (DOR). Dilution factors of 1.25, 2, 5, 10, 25 and 50 (DEX at 30 microM) gave mean (+/-SE) values of k(inact) (min-1) of 0.20+/-0.06, 0.21+/-0.05, 0.31+/-0.06, 0.37+/-0.11, 0.51+/-0.10 and 0.58+/-0.08, respectively, and KI (microM) values (after correction for non-specific microsomal binding) of 2.22+/-1.90, 2.80+/-1.34, 5.78+/-2.07, 6.36+/-2.93, 3.99+/-1.57 and 4.86+/-1.37, respectively. Accordingly, high (e.g. 50 fold) and low (e.g. 1.25 fold) dilutions were associated with statistically significant differences in kinetic values (p <0.05). Varying DEX concentration (10-100 microM) was not associated with significant changes in k(inact) and KI values when a five-fold dilution was used (with the exception of a lower KI at 10 microM DEX). High dilution was also shown to reduce non-specific microsomal binding of MDMA. The changes in the two kinetic parameters were dependent on the experimental procedure and shown to be unlikely to have a material influence on the maximum inhibition of CYP2D6 expected in vivo after typical recreational doses of MDMA (50-100 mg), since the potency of inhibition was high. The different values of the kinetic parameters were predicted to have a marginal influence on the time for recovery of enzyme activity following re-synthesis of CYP2D6.
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Affiliation(s)
- Linh M Van
- Academic Unit of Clinical Pharmacology, University of Sheffield, Pharmacokinetics and Pharmacogenetics Group, Division of Clinical Sciences (South), Sheffield, UK
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Heydari A, Yeo KR, Lennard MS, Ellis SW, Tucker GT, Rostami-Hodjegan A. Mechanism-based inactivation of CYP2D6 by methylenedioxymethamphetamine. Drug Metab Dispos 2004; 32:1213-7. [PMID: 15328252 DOI: 10.1124/dmd.104.001180] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The potency of methylenedioxymethamphetamine (MDMA) as a mechanism-based inhibitor of CYP2D6 has been defined using microsomes prepared from yeast expressing the enzyme and from three human livers. The inhibitory effect was increased by preincubation through formation of a metabolic intermediate complex. Inactivation parameters (kinact and KI), defined with respect to the O-demethylation of dextromethorphan, were 0.29 +/- 0.03 (S.E.) min(-1) and 12.9 +/- 3.6 (S.E.) microM for yeast-expressed CYP2D6, and 0.26 +/- 0.02 min(-1) and 14.4 +/- 2.5 microM, 0.15 +/- 0.01 min(-1) and 8.8 +/- 2.6 microM, and 0.12 +/- 0.05 min(-1) and 45.3 +/- 32.1 microM for the liver microsomal preparations. The rate of inactivation of CYP2D6 by MDMA decreased when quinidine, a competitive inhibitor of CYP2D6, was added to the primary incubation mixture. However, inactivation was unaffected by the addition of glutathione. The results indicate that MDMA is a potent mechanism-based inhibitor of CYP2D6, with implications for understanding its in vivo disposition and drug interaction potential.
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Affiliation(s)
- A Heydari
- Division of Clinical Sciences (South), University of Sheffield, UK
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4
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Daly AK. Development of analytical technology in pharmacogenetic research. Naunyn Schmiedebergs Arch Pharmacol 2003; 369:133-40. [PMID: 14513205 DOI: 10.1007/s00210-003-0794-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2003] [Accepted: 07/28/2003] [Indexed: 12/15/2022]
Abstract
Methods used to determine phenotype and genotype for pharmacogenetic polymorphisms are discussed. Phenotyping is mainly applicable to polymorphisms affecting drug disposition rather than drug response and can involve either direct measurement of enzyme activity or administration of a probe drug followed by measurement of drug and/or metabolite levels. Genotyping is now more widely used than phenotyping and can be used to determine genotype for polymorphisms affecting either drug disposition (for example those in the cytochromes P450 or N-acetyltransferases) or drug response (for example those in drug receptors). Most genotyping for known polymorphisms involves use of the polymerase chain reaction and the wide variety of methods based on this technique that are now used for routine genotyping are discussed in detail. In addition, a range of methods that can be used to detect novel polymorphisms, thereby further increasing understanding of interindividual variability in drug disposition and response, is described.
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Affiliation(s)
- Ann K Daly
- Pharmacogenetics Group, School of Clinical and Laboratory Sciences, Medical School, University of Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK.
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Bendriss EK, Markoglou N, Wainer IW. High-performance liquid chromatography assay for simultaneous determination of dextromethorphan and its main metabolites in urine and in microsomal preparations. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 2001; 754:209-15. [PMID: 11318417 DOI: 10.1016/s0378-4347(00)00609-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
An HPLC method has been developed and validated for the determination of dextromethorphan, dextrorphan, 3-methoxymorphinan and 3-hydroxymorphinan in urine samples. Deconjugated compounds were extracted on silica cartridges using dichloromethane/hexane (95:05, v/v) as an eluent. Chromatographic separation was accomplished on a Phenyl analytical column serially connected with a Nitrile analytical column. The mobile phase consisted of a mixture of an aqueous solution, containing 1.5% acetic acid and 0.1% triethylamine, and acetonitrile (75:25, v/v). Compounds were monitored using a fluorescence detector. Calibration curves were linear over the range investigated (0.2-8.0 microM) with correlation coefficients >0.999. The method was reproducible and precise. Coefficients of variation and deviations from nominal values were both below 10%. For all the analytes, recoveries exceeded 77% and the limits of detection were 0.01 microM. The validated assay proved to be suitable for the determination of DEM metabolic indexes reported to reflect the enzymatic activity of the cytochrome P450s, CYP2D6 and CYP3A, both in vivo, when applied to urine samples from patients, and in vitro, when applied to samples from the incubation of liver microsomes with dextromethorphan.
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Affiliation(s)
- E K Bendriss
- Department of Oncology, McGill University, Montréal, Québec, Canada
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Chow MS, White CM, Lau CP, Fan C, Tang MO. Evaluation of CYP2D6 oxidation of dextromethorphan and propafenone in a Chinese population with atrial fibrillation. J Clin Pharmacol 2001; 41:92-6. [PMID: 11144999 DOI: 10.1177/00912700122009737] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The objective of this study was to determine the percentage of patients with paroxysmal atrial fibrillation who were poor metabolizers of CYP2D6 in a Chinese population from Hong Kong and to assess the relationship between the dextromethorphan/dextrorphan ratio and the propafenone/5-hydroxypropafenone ratio or the steady-state propafenone concentration. Patients (n = 60) were recruited from the Arrhythmia Clinic at the University of Hong Kong and given dextromethorphan 30 mg. The dextromethorphan and dextrorphan concentrations in urine over the next 8 hours were used to determine metabolizer status. If the metabolic ratio was greater than 0.3, the patient was determined to be a poor metabolizer. In phase 2, patients (n = 38) were given propafenone 150 mg twice daily, and at steady state, the propafenone and 5-OH propafenone plasma concentrations were determined. It was found that 15% of the patients were poor metabolizers of dextromethorphan. There was a significant correlation between the metabolic ratios of dextromethorphan/dextrorphan and propafenone/5-OH propafenone (r = 0.49, p = 0.0019) and between the dextromethorphan/dextrorphan ratio and the concentration of propafenone (r = 0.32, p = 0.05). No correlations were found in the extensive or poor metabolizer subgroups. It was concluded that the percentage of poor metabolizers in atrial fibrillation patients from Hong Kong was much larger than in previous studies of Chinese patients who were not from Hong Kong. The ability to metabolize dextromethorphan to dextrorphan is related to the ability to metabolize propafenone to 5-hydroxypropafenone.
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Affiliation(s)
- M S Chow
- Department of Pharmacy, Faculty of Medicine, Chinese University of Hong Kong, Shatin, NT, Hong Kong
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Tran A, Rey E, Pons G, Rousseau M, d'Athis P, Olive G, Mather GG, Bishop FE, Wurden CJ, Labroo R, Trager WF, Kunze KL, Thummel KE, Vincent JC, Gillardin JM, Lepage F, Levy RH. Influence of stiripentol on cytochrome P450-mediated metabolic pathways in humans: in vitro and in vivo comparison and calculation of in vivo inhibition constants. Clin Pharmacol Ther 1997; 62:490-504. [PMID: 9390105 DOI: 10.1016/s0009-9236(97)90044-8] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
OBJECTIVE The spectrum of cytochrome P450 inhibition of stiripentol, a new anticonvulsant, was characterized in vitro and in vivo. METHODS Stiripentol was incubated in vitro with (R)-warfarin, coumarin, (S)-warfarin, (S)-mephenytoin, bufuralol, p-nitrophenol, and carbamazepine as probes for CYPs 1A2, 2A6, 2C9, 2C19, 2D6, 2E1, and 3A4, respectively. Caffeine demethylation and the 6 beta-hydroxycortisol/cortisol ratio were monitored in vivo before and after 14 days of treatment with stiripentol as measures of CYP1A2 and CYP3A4 activity, and dextromethorphan O- and N-demethylation were used to measure CYP2D6 and CYP3A4 activity, respectively. In vivo inhibition constants for CYP3A4 were calculated with use of data that previously documented the interaction between stripentol and carbamazepine. RESULTS In vitro, stiripentol inhibited CYPs 1A2, 2C9, 2C19, 2D6, and 3A4, with inhibition constant values at or slightly higher than therapeutic (total) concentrations of stiripentol, but it did not inhibit CYPs 2A6 and 2E1 even at tenfold therapeutic concentrations. In vivo inhibition of caffeine demethylation and dextromethorphan N-demethylation were consistent with inhibition of CYP1A2 and CYP3A4, respectively. The 6 beta-hydroxycortisol/cortisol ratio did not provide a reliable index of CYP3A4 inhibition. Inhibition of CYP2D6-mediated O-demethylation was not observed in vivo. With use of carbamazepine, in vivo inhibition constants for CYP3A4 ranged between 12 and 35 mumol/L, whereas the corresponding in vitro value was 80 mumol/L. CONCLUSIONS Stiripentol appears to inhibit several CYP450 enzymes in vitro and in vivo. In vivo inhibition constants show that stiripentol inhibition of CYP3A4 is linearly related to plasma concentration in patients with epilepsy.
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Affiliation(s)
- A Tran
- Département de Pharmacologie Périnatale et Pédiatrique, Hôpital Saint Vincent de Paul-Université René Descartes Paris V
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8
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Jurima-Romet M, Foster BC, Casley WL, Rode A, Vloshinsky P, Huang HS, Geertsen S. CYP2D6-related oxidation polymorphism in a Canadian Inuit population. Can J Physiol Pharmacol 1997. [DOI: 10.1139/y97-013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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9
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Bartoletti RA, Belpaire FM, Rosseel MT. High performance liquid chromatography determination of dextromethorphan and its metabolites in urine using solid-phase extraction. J Pharm Biomed Anal 1996; 14:1281-86. [PMID: 8818046 DOI: 10.1016/s0731-7085(95)01749-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A high performance liquid chromatography assay coupled with fluorescence detection was developed for the determination of dextromethorphan and its metabolites in urine. The products and the internal standard, pholcodine, were separated on an Alltima C18, 5 microns column (250 x 4.6 mm), using a mobile phase containing sodium dodecyl sulphate (1 mM) in a mixture of acetonitrile-sodium dihydrogen phosphate (0.01 M) 40.5:59.5, v/v) (pH* = 2.5). A novel solid-phase extraction procedure with strong cation exchange, non end-capped, Isolute SCX cartridges allows good recovery of the products (mean 85% or more). For all analytes, the assay is sensitive (LOQ 25 ng ml-1, using 200 microliters urine), reproducible (RSD < 15%) and accurate (< 15% deviation of the nominal value) over the range evaluated. This method can be used to measure dextromethorphan and its metabolites to phenotype individuals as poor or extensive metabolizers of drugs metabolized by CYP2D6.
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Affiliation(s)
- R A Bartoletti
- Heymans Institute of Pharmacology, University of Gent Medical School, Belgium
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10
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Kévorkian JP, Michel C, Hofmann U, Jacqz-Aigrain E, Kroemer HK, Peraldi MN, Eichelbaum M, Jaillon P, Funck-Brentano C. Assessment of individual CYP2D6 activity in extensive metabolizers with renal failure: comparison of sparteine and dextromethorphan. Clin Pharmacol Ther 1996; 59:583-92. [PMID: 8646830 DOI: 10.1016/s0009-9236(96)90187-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVES To examine whether the variability of CYP2D6 activity in patients with chronic renal failure can be assessed, particularly among subjects with the extensive metabolizer phenotype, by use of standard in vivo indexes of CYP2D6 activity derived from oral administration of dextromethorphan and sparteine. METHODS A single 100 mg oral dose of sparteine and a single 40 mg oral dose of dextromethorphan were administered on two occasions to 12 patients with chronic renal failure (creatinine clearance ranging from 20 to 70 ml/min) and 12 age- and sex-matched healthy subjects. Sparteine clearances, sparteine metabolic ratio, and urinary recovery of dextrorphan were calculated. Patients and healthy control subjects were not selected on the basis of their CYP2D6 phenotypes. RESULTS Chronic renal failure was associated with a decrease in sparteine partial metabolic clearance to dehydrosparteine (median of 322 ml/min and range of 62 to 670 ml/min in patients with renal failure versus median of 635 ml/min and range of 77 to 1276 ml/min in normal subjects; p < 0.02). Sparteine apparent oral clearance (p < 0.03) and renal clearance (p < 0.001) decreased in patients with renal failure. However, sparteine metabolic ratio was not significantly altered in patients with renal failure and showed that all patients were extensive metabolizers of sparteine. Although fractional urinary excretion of dextrorphan decreased in patients with renal failure (median, 24.4%; range, 9.7% to 55.9%) compared with control (median, 47.5%; range, 24.1% to 72.1%) (p = 0.02), it also showed that all subjects were extensive metabolizers of dextromethorphan. The amount of dextromethorphan excreted in urine correlated with creatinine clearance independently from CYP2D6 activity measured as sparteine partial metabolic clearance. However, it did not correlate with sparteine metabolic ratio or with fractional urinary excretion of dehydrosparteine. CONCLUSION Assessment of CYP2D6 activity by use of dextromethorphan and sparteine is possible in extensive metabolizer patients with chronic renal failure. However, in these subjects, dextromethorphan and sparteine do not reflect CYP2D6 activity in the same way.
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Affiliation(s)
- J P Kévorkian
- Clinical Pharmacology Unit, Saint-Antoine University Hospital, Paris, France
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Ducharme J, Abdullah S, Wainer IW. Dextromethorphan as an in vivo probe for the simultaneous determination of CYP2D6 and CYP3A activity. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL APPLICATIONS 1996; 678:113-28. [PMID: 8861661 DOI: 10.1016/0378-4347(95)00574-9] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Dextromethorphan (DM) is O-demethylated into dextrorphan (DEX) in humans by the cytochrome P450 designated as CYP2D6 and N-demethylated into 3-methoxymorphinan (3MM) via CYP3As. Clinically, DM has been successfully used as an index of CYP2D6 and this paper describes analytical and clinical data that will help evaluate the use of DM hydrobromide as a probe of CYP3A activity. DM and its three demethylated metabolites were measured in a 4-h spot urine sample using a HPLC method employing solid-phase extraction (C(18)), analysis on a phenyl column [mobile phase, methanol-acetonitrile-phosphate buffer (10 mM, pH 3.5, 20:25:55, v/v)] and fluorescence detection (excitation at lambda=228 nm, no emission cut-off filter). The urinary molar ratio DM-DEX was used to assess CYP2D6 activity while DM-3MM was used for CYP3As. The DM-3MM ratios were sensitive to the co-administration of selective CYP3A inhibitors grapefruit juice and erythromycin. In addition, in healthy volunteers and cancer patients, the N-demethylation of DM correlated with the CYP3A-mediated metabolism of verapamil and tamoxifen. DM appears to be a promising way to simultaneously phenotype patients for CYP2D6 and CYP3As.
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Affiliation(s)
- J Ducharme
- Department of Oncology, McGill University, Montreal General Hospital, Quebec, Canada
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Laurent-Kenesi MA, Funck-Brentano C, Poirier JM, Decolin D, Jaillon P. Influence of CYP2D6-dependent metabolism on the steady-state pharmacokinetics and pharmacodynamics of metoprolol and nicardipine, alone and in combination. Br J Clin Pharmacol 1993; 36:531-8. [PMID: 12959269 PMCID: PMC1364657 DOI: 10.1111/j.1365-2125.1993.tb00411.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
1 The metabolism of metoprolol depends in part on the genetically determined activity of the CYP2D6 isoenzyme. In vitro studies have shown that nicardipine is a potent inhibitor of CYP2D6 activity. Since the combination of metoprolol and nicardipine is likely to be used for the treatment of hypertension, we examined the interaction between these two drugs at steady-state. 2 Fourteen healthy volunteers, seven extensive and seven poor metabolisers of dextromethorphan were studied in a double-blind, randomised cross-over four-period protocol. Subjects received nicardipine 50 mg every 12 h, metoprolol 100 mg every 12 h, a combination of both drugs and placebo during 5.5 days. Steady-state pharmacokinetics of nicardipine and metoprolol were analyzed. Beta-adrenoceptor blockade was assessed as the reduction of exercise-induced tachycardia. 3 During treatment with metoprolol, alone or in combination with nicardipine, its steady-state plasma concentrations were higher in subjects of the poor metaboliser phenotype than in extensive metabolisers. Beta-adrenoceptor blockade was also more pronounced in poor metabolisers than in extensive metabolisers of dextromethorphan during treatment with metoprolol alone or in combination with nicardipine (24.0 +/- 2.4% vs 17.1 +/- 3.5% and 24.1 +/- 2.5% vs 15.4 +/- 2.7% reduction in exercise trachycardia, respectively, P < 0.01 in each case). 4 Nicardipine produced a small increase in plasma metoprolol concentration in extensive metabolisers from 35.9 +/- 16.6 to 45.8 +/- 15.4 ng ml(-1) (P < 0.02), but had no significant effect in poor metabolisers. However, nicardipine did not alter the R/S metoprolol ratio in plasma 3 h after dosing, the plasma concentration of S-(-)-metoprolol 3 h after dosing or the beta-adrenoceptor blockade produced by metoprolol in subjects of both phenotypes. The partial metabolic clearance of metoprolol to alpha-hydroxy-metoprolol was not altered significantly in extensive metabolisers. Plasma nicardipine concentration and beta-adrenoceptor blocking effects did not differ between the phenotypes and were not influenced by metoprolol. We conclude that beta-adrenoceptor blockade during repeated dosing with metoprolol is more pronounced in poor than in extensive metaboliser subjects, that nicardipine decreases a CYP2D6-independent route of metoprolol elimination but does not increase beta-adrenoceptor blockade during repeated dosing with metoprolol.
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Affiliation(s)
- M A Laurent-Kenesi
- Clinical Pharmacology Unit, Saint-Antoine University Hospital, Paris, France
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13
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Treluyer JM, Jacqz-Aigrain E, Alvarez F, Cresteil T. Expression of CYP2D6 in developing human liver. EUROPEAN JOURNAL OF BIOCHEMISTRY 1991; 202:583-8. [PMID: 1722149 DOI: 10.1111/j.1432-1033.1991.tb16411.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The CYP2D6 protein is a polymorphic isoenzyme involved in the biotransformation of several drugs including the probe drug dextromethorphan. The rise in the protein concentration, immunochemically determined with a specific antibody, was shown to occur within the first week following birth, whatever the gestational age at birth. In fetuses, the concentration of hepatic CYP2D6 protein was very low or undetectable in 70% of samples tested. In the remaining 30%, its concentration was comparable to that of newborns aged 1-7 days. This early rise was associated with spontaneous abortion in 70% of positive samples, whereas in fetuses with an intermediate CYP2D6 protein concentration, 80% were from induced abortions. The rise in CYP2D6 protein was associated with the developmental onset of dextromethorphan O-demethylation, but not N-demethylation, even if activity was lower in fetal than in neonatal and in adult liver microsomes. Lastly, the CYP2D6 RNA is detectable earlier than the protein and exhibits a peak of hepatic accumulation in newborns, before declining in adulthood. A positive correlation between RNA accumulation and protein concentration can be demonstrated only in the adult. This suggest that regulation is primarily at the transcriptional level, but cannot rule out the participation of post-transcriptional events in the regulation process throughout ontogenesis.
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Affiliation(s)
- J M Treluyer
- Institut National de la Santé et de la Recherche Médicale U75, Paris, France
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14
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Jacqz-Aigrain E, Gueguen M, Zanger UM, Robieux I, Alvarez F. Cytochrome P450IID subfamily in non-human primates. Catalytical and immunological characterization. Biochem Pharmacol 1991; 41:1657-63. [PMID: 2043154 DOI: 10.1016/0006-2952(91)90166-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Interindividual variations of debrisoquine metabolism was recently identified in non-human primates tested in vivo. The catalytical and immunological characterization of cytochrome P450IID subfamily was undertaken in hepatic microsomes from extensive metabolizer primates. The NADPH/O2 mediated metabolism of debrisoquine, dextromethorphan and bufuralol was similar to the kinetics reported in humans. The CuOOH mediated metabolism of bufuralol suggested that at least two enzymes are responsible for bufuralol 1'-hydroxylation. Eleven compounds were tested for their capacity to modify P450IID function in vitro. Eight competitive inhibitors of P450IID6 in man were all and exclusively competitive inhibitor of P450IID subfamily in non-human primates. Quinidine, which is the strongest competitive inhibitor in man, exhibited the higher inhibitory potency in monkey (Ki = 0.75 microM). Anti-LKM antibody against P450IID subfamily cross-reacted with two proteins of 49 and 47 kDa, and sera containing anti-LKM antibody against these two proteins inhibited dextrorphan formation in vitro. These data provide evidence for catalytical and immunological similarities between human and monkey microsomes and indicate that the primate system could be a model for enzymatic studies of P450IID.
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Affiliation(s)
- E Jacqz-Aigrain
- Unité de Pharmacologie Clinique, Hôpital Robert-Debre, Paris, France
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15
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Jacqz-Aigrain E, Laurent J, Alvarez F. Dextromethorphan phenotypes in paediatric patients with autoimmune hepatitis. Br J Clin Pharmacol 1990; 30:153-4. [PMID: 2390427 PMCID: PMC1368290 DOI: 10.1111/j.1365-2125.1990.tb03758.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- E Jacqz-Aigrain
- Pharmacologie Clinique, Inserm U.120, Hôpital Robert-Debré, Paris, France
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