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Frontiers in Pharmacology 2023Pharmacogenetics-informed drug prescribing is increasingly applied in clinical practice. Typically, drug metabolizing phenotypes are determined based on genetic test...
Pharmacogenetics-informed drug prescribing is increasingly applied in clinical practice. Typically, drug metabolizing phenotypes are determined based on genetic test results, whereupon dosage or drugs are adjusted. Drug-drug-interactions (DDIs) caused by concomitant medication can however cause mismatches between predicted and observed phenotypes (phenoconversion). Here we investigated the impact of genotype on the outcome of CYP2C19-dependent DDIs in human liver microsomes. Liver samples from 40 patients were included, and genotyped for *2, *3 and *17 variants. S-mephenytoin metabolism in microsomal fractions was used as proxy for CYP2C19 activity, and concordance between genotype-predicted and observed CYP2C19 phenotype was examined. Individual microsomes were subsequently co-exposed to fluvoxamine, voriconazole, omeprazole or pantoprazole to simulate DDIs. Maximal CYP2C19 activity (V) in genotype-predicted intermediate metabolizers (IMs; *1/*2 or *2/*17), rapid metabolizers (RMs; *1/*17) and ultrarapid metabolizers (UMs; *17/*17) was not different from V of predicted normal metabolizers (NMs; *1/*1). Conversely, *2/*2 genotyped-donors exhibited V rates ∼9% of NMs, confirming the genotype-predicted poor metabolizer (PM) phenotype. Categorizing CYP2C19 activity, we found a 40% concordance between genetically-predicted CYP2C19 phenotypes and measured phenotypes, indicating substantial phenoconversion. Eight patients (20%) exhibited CYP2C19 IM/PM phenotypes that were not predicted by their CYP2C19 genotype, of which six could be linked to the presence of diabetes or liver disease. In subsequent DDI experiments, CYP2C19 activity was inhibited by omeprazole (-37% ± 8%), voriconazole (-59% ± 4%) and fluvoxamine (-85% ± 2%), but not by pantoprazole (-2 ± 4%). The strength of CYP2C19 inhibitors remained unaffected by genotype, as similar percental declines in CYP2C19 activity and comparable metabolism-dependent inhibitory constants (K/K) of omeprazole were observed between CYP2C19 genotypes. However, the consequences of CYP2C19 inhibitor-mediated phenoconversion were different between genotypes. In example, voriconazole converted 50% of *1/*1 donors to a IM/PM phenotype, but only 14% of *1/*17 donors. Fluvoxamine converted all donors to phenotypic IMs/PMs, but *1/*17 (14%) were less likely to become PMs than *1/*1 (50%) or *1/*2 and *2/*17 (57%). This study suggests that the differential outcome of CYP2C19-mediated DDIs between genotypes are primarily dictated by basal CYP2C19 activity, that may in part be predicted by genotype but likely also depends on disease-related factors.
PubMed: 37361233
DOI: 10.3389/fphar.2023.1201906 -
Scientific Reports Feb 2022Human CYP2B6 enzyme although constitutes relatively low proportion (1-4%) of hepatic cytochrome P450 content, it is the major catalyst of metabolism of several...
Human CYP2B6 enzyme although constitutes relatively low proportion (1-4%) of hepatic cytochrome P450 content, it is the major catalyst of metabolism of several clinically important drugs (efavirenz, cyclophosphamide, bupropion, methadone). High interindividual variability in CYP2B6 function, contributing to impaired drug-response and/or adverse reactions, is partly elucidated by genetic polymorphisms, whereas non-genetic factors can significantly modify the CYP2B6 phenotype. The influence of genetic and phenoconverting non-genetic factors on CYP2B6-selective activity and CYP2B6 expression was investigated in liver tissues from Caucasian subjects (N = 119). Strong association was observed between hepatic S-mephenytoin N-demethylase activity and CYP2B6 mRNA expression (P < 0.0001). In less than one third of the tissue donors, the CYP2B6 phenotype characterized by S-mephenytoin N-demethylase activity and/or CYP2B6 expression was concordant with CYP2B6 genotype, whereas in more than 35% of the subjects, an altered CYP2B6 phenotype was attributed to phenoconverting non-genetic factors (to CYP2B6-specific inhibitors and inducers, non-specific amoxicillin + clavulanic acid treatment and chronic alcohol consumption, but not to the gender). Furthermore, CYP2B6 genotype-phenotype mismatch still existed in one third of tissue donors. In conclusion, identifying potential sources of CYP2B6 variability and considering both genetic variations and non-genetic factors is a pressing requirement for appropriate elucidation of CYP2B6 genotype-phenotype mismatch.
Topics: Alleles; Cytochrome P-450 CYP2B6; Gene Expression; Genotype; Humans; Liver; Phenotype; Polymorphism, Genetic; RNA, Messenger; White People
PubMed: 35194103
DOI: 10.1038/s41598-022-07022-9 -
Toxins Jul 2022Beauvericin (BEA) is a well-known mycotoxin produced by many fungi, including Beaveria bassiana. The purpose of this study was to evaluate the in vitro distribution and...
Beauvericin (BEA) is a well-known mycotoxin produced by many fungi, including Beaveria bassiana. The purpose of this study was to evaluate the in vitro distribution and metabolism characteristics as well as the in vivo pharmacokinetic (PK) profile of BEA. The in vitro metabolism studies of BEA were performed using rat, dog, mouse, monkey and human liver microsomes, cryopreserved hepatocytes and plasma under conditions of linear kinetics to estimate the respective elimination rates. Additionally, LC-UV-MSn (n = 1~2) was used to identify metabolites in human, rat, mouse, dog and monkey liver microsomes. Furthermore, cytochrome P450 (CYP) reaction phenotyping was carried out. Finally, the absolute bioavailability of BEA was evaluated by intravenous and oral administration in rats. BEA was metabolically stable in the liver microsomes and hepatocytes of humans and rats; however, it was a strong inhibitor of midazolam 1′-hydroxylase (CYP3A4) and mephenytoin 4′-hydroxylase (CYP2C19) activities in human liver microsomes. The protein binding fraction values of BEA were >90% and the half-life (T1/2) values of BEA were approximately 5 h in the plasma of the five species. The absolute bioavailability was calculated to be 29.5%. Altogether, these data indicate that BEA has great potential for further development as a drug candidate. Metabolic studies of different species can provide important reference values for further safety evaluation.
Topics: Animals; Biological Availability; Cytochrome P-450 Enzyme System; Depsipeptides; Dogs; Humans; Mice; Microsomes, Liver; Pharmaceutical Preparations; Rats
PubMed: 35878215
DOI: 10.3390/toxins14070477 -
Basic & Clinical Pharmacology &... May 2020There is evidence that the antipsychotic drug perazine is an inhibitor of CYP2D6. This study aimed at evaluating its effect on CYP2D6 and CYP2C19 activities in...
There is evidence that the antipsychotic drug perazine is an inhibitor of CYP2D6. This study aimed at evaluating its effect on CYP2D6 and CYP2C19 activities in submitting psychiatric patients to phenotyping with dextromethorphan and mephenytoin, respectively, substrates of these enzymes, before and during a treatment with perazine. A total of 31 patients were phenotyped with dextromethorphan (CYP2D6) and mephenytoin (CYP2C19) before and after a 2-week treatment with 450 ± 51 mg/day (mean ± sd) perazine. At baseline, five patients appeared to be poor metabolizers (PM) of dextromethorphan and two patients of mephenytoin. The metabolic ratio (MR) of dextromethorphan/dextrorphan as determined in collected urine increased significantly (Wilcoxon; P < .0001) from baseline (0.39 ± 1.38 [mean ± sd]) till day 14 (1.46 ± 2.22). In 19 out of 26 extensive metabolizers (EM) of dextromethorphan, the phenotype changed from EM to PM. This suggests an almost complete inhibition of CYP2D6 by perazine and/or its metabolites. On the other hand, perazine (or some of its metabolites) did seemingly not inhibit CYP2C19. In conclusion, this study suggests that in patients treated with perazine and co-medicated with CYP2D6 substrates, there could be an increased risk of adverse effects as a consequence of a pharmacokinetic interaction.
Topics: Adult; Antipsychotic Agents; Cytochrome P-450 CYP2C19; Cytochrome P-450 CYP2D6; Cytochrome P-450 CYP2D6 Inhibitors; Dextromethorphan; Drug Interactions; Female; Humans; Male; Mephenytoin; Middle Aged; Perazine; Phenotype; Schizophrenia; Young Adult
PubMed: 31814297
DOI: 10.1111/bcpt.13373 -
Journal of Psychiatry & Neuroscience :... Jan 1994In neurochemistry there are advantages in determining how patients are likely to react to psychoactive drugs prior to the commencement of drug therapy. Explanations of a... (Review)
Review
In neurochemistry there are advantages in determining how patients are likely to react to psychoactive drugs prior to the commencement of drug therapy. Explanations of a patient's nonresponse, or unexpected adverse reactions to drugs are required. In many instances, a knowledge of the drug metabolism status of a patient can be helpful in the selection of a drug and its dosage regimen, and in the prediction of possible drug/drug interactions when two or more drugs have to be administered concomitantly. Important information on these topics may be obtained by phenotyping patients prior to drug therapy. The metabolism of various antidepressant and neuroleptic drugs is catalyzed by CYP2D6, a cytochrome P450 isozyme (also named P450IID6), whereas the metabolism of other drugs may involve different cytochromes P450. The properties of CYP2D6 and four other isozymes (CYP1A1, CYP1A2, CYP2C8/9 and CYP3A4) are described, and substrates identified. Phenotyping of patients for CYP2D6 activity and mephenytoin hydroxylase activity is described.
Topics: Clomipramine; Cytochromes; Dealkylation; Depressive Disorder; Desipramine; Dextromethorphan; Drug Interactions; Female; Humans; Hydroxylation; Imipramine; Isoenzymes; Male; Mephenytoin; Nortriptyline; Phenotype; Polymorphism, Genetic
PubMed: 8148364
DOI: No ID Found -
Frontiers in Pharmacology 2023Vortioxetine is a novel anti-major depression disorder drug with a high safety profile compared with other similar drugs. However, little research has been done on...
Vortioxetine is a novel anti-major depression disorder drug with a high safety profile compared with other similar drugs. However, little research has been done on drug-drug interactions (DDI) about vortioxetine. In this paper, the inhibitory effect of vortioxetine on cytochrome P450 (CYP450) and the type of inhibitory mechanism were investigated in human and rat liver microsomes. We set up an incubation system of 200 μL to measure the metabolism of probe substrates at the present of vortioxetine at 37°C. The concentrations of the metabolites of probe substrates were all measured by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method. It was found no time-dependent inhibition (TDI) of vortioxetine through determination of half-maximal inhibitory concentration (IC) shift values. The enzymes and metabolites involved in this experiment in human and rats were as follows: CYP3A4/CYP3A (midazolam); CYP2B6/CYP2B (bupropion); CYP2D6/CYP2D (dextromethorphan); CYP2C8/CYP2C-1 (amodiaquine); CYP2C9/CYP2C-2 (losartan); and CYP2C19/CYP2C-3 (mephenytoin). We found that vortioxetine competitively inhibited CYP2C19 and CYP2D6 in human liver microsomes (HLMs) with inhibition constant (K) values of 2.17 μM and 9.37 μM, respectively. It was noncompetitive inhibition for CYP3A4 and CYP2C8, and its K values were 7.26 μM and 6.96 μM, respectively. For CYP2B6 and CYP2C9, vortioxetine exhibited the mixed inhibition with K values were 8.55 μM and 4.17 μM, respectively. In RLMs, the type of vortioxetine inhibition was uncompetitive for CYP3A and CYP2D (K = 4.41 and 100.9 μM). The inhibition type was competitive inhibition, including CYP2B and CYP2C-2 (K = 2.87 and 0.12 μM). The inhibition types of CYP2C-1 and CYP2C-3 (K = 39.91 and 4.23 μM) were mixed inhibition and noncompetitive inhibition, respectively. The study of the above mechanism will provide guidance for the safe clinical use of vortioxetine so that the occurrence of DDI can be avoided.
PubMed: 37790811
DOI: 10.3389/fphar.2023.1199548 -
British Journal of Clinical Pharmacology Jun 19901. In a phenotyped panel of healthy subjects correlations were studied between the oxidation of mephenytoin, phenytoin, methylphenytoin and phenobarbitone, with respect...
Relationship between mephenytoin oxidation polymorphism and phenytoin, methylphenytoin and phenobarbitone hydroxylation assessed in a phenotyped panel of healthy subjects.
1. In a phenotyped panel of healthy subjects correlations were studied between the oxidation of mephenytoin, phenytoin, methylphenytoin and phenobarbitone, with respect to the formation of their 4-hydroxy metabolites (OH-). 2. On different occasions phenotyped extensive metabolizers (EM; n = 16) and poor metabolizers (PM; n = 4) of mephenytoin received phenytoin (100 mg), methylphenytoin (100 mg) and phenobarbitone (50 mg) and urine was collected up to 24 h. The excreted 4-hydroxy metabolites of all compounds were measured by h.p.l.c. 3. Urinary recovery of OH-phenytoin was 31.0 +/- 11.7%, of OH-methylphenytoin 3.4 +/- 2.7% and of OH-phenobarbitone 1.4 +/- 1.2%. No correlation was found between the recovery of OH-mephenytoin and OH-phenytoin. A subject who produced virtually no OH-phenytoin was an EM of mephenytoin, confirming a dissociation of mephenytoin polymorphism and phenytoin hydroxylation. 4. The correlation coefficient for OH-mephenytoin and OH-methylphenytoin recovery was 0.71 (Spearman rank, P = 0.002). The PMs of mephenytoin excreted the least amount of OH-methylphenytoin, suggesting a cosegregation of the 4-hydroxylation pathways. No correlation was found between the urinary recovery of OH-phenobarbitone and that of the other 4-hydroxy metabolites.
Topics: Adult; Female; Humans; Hydantoins; Hydroxylation; Male; Mephenytoin; Oxidation-Reduction; Phenobarbital; Phenotype; Phenytoin
PubMed: 2378787
DOI: 10.1111/j.1365-2125.1990.tb03687.x -
British Journal of Clinical Pharmacology Apr 2013To determine the effect of increasing adult age on predicted metabolic drug clearance.
AIM
To determine the effect of increasing adult age on predicted metabolic drug clearance.
METHOD
Predicted metabolic drug clearances (CLPT ) were determined using in vitro-in vivo extrapolation coupled with physiological-based pharmacokinetic modelling and simulation (IVIVE-PBPK) in Simcyp®. Simulations were conducted using CYP-selective 'probe' drugs with subjects in 5 year age groups (20-25 to 90-95 years). CLPT values were compared with human pharmacokinetic data stratified according to age (young = 20-40 years and elderly = 65-85 years) and gender. Age-related changes in the physiological parameters used for IVIVE of CLPT were described.
RESULTS
Predicted metabolic drug clearances decreased with increasing adult age to approximately 65-70 years: caffeine from 1.5 to 1.0 ml min(-1) kg(-1) (a 33% decrease), S-warfarin from 0.100 to 0.064 ml min(-1) kg(-1) (36%), S-mephenytoin from 4.1 to 2.5 ml min(-1) kg(-1) (39%), desipramine from 10.6 to 7.3 ml min(-1) kg(-1) (31%) and midazolam from 5.4 to 3.9 ml min(-1) kg(-1) (27%). Except for S-mephenytoin, predictions were within 3.5-fold of clearances from clinical studies when stratified by age and gender. A trend towards higher CLPT was observed in females, but this was only statistically significant in larger virtual trials. Physiological parameters that determine CLPT decreased with increasing adult age: mean microsomal protein g(-1) of liver, liver weight, hepatic blood flow and human serum albumin concentration.
CONCLUSION
Decreased metabolic clearance in the elderly was predicted by Simcyp® and was generally consistent with limited clinical data for four out of five drugs studied and the broader literature for drugs metabolized by CYP enzymes. IVIVE-PBPK may be increasingly useful in predicting metabolic drug clearance in the elderly.
Topics: Adult; Aged; Aged, 80 and over; Aging; Caffeine; Computer Simulation; Desipramine; Female; Humans; Male; Mephenytoin; Metabolic Clearance Rate; Midazolam; Middle Aged; Models, Biological; Warfarin
PubMed: 22924488
DOI: 10.1111/j.1365-2125.2012.04446.x -
The Yale Journal of Biology and Medicine 1996Omeprazole, lansoprazole and pantoprazole are metabolized by several human cytochromes P450, most prominently by CYP2C19 and CYP3A4. Only pantoprazole is also... (Review)
Review
Omeprazole, lansoprazole and pantoprazole are metabolized by several human cytochromes P450, most prominently by CYP2C19 and CYP3A4. Only pantoprazole is also metabolized by a sulfotransferase. Differences in the quantitative contribution of these enzymes and in the relative affinities of the substrates explain some of the observed interactions with carbamazepin, diazepam, phenytoin and theophylline and of the impact of the CYP2C19 (mephenytoin) genetic polymorphism. Of these drugs, pantoprazole has the lowest potential for interactions, both in vitro and in human volunteer studies.
Topics: Animals; Cytochrome P-450 Enzyme System; Drug Interactions; Humans; Proton Pump Inhibitors; Proton Pumps
PubMed: 9165689
DOI: No ID Found -
British Journal of Clinical Pharmacology Aug 1999To compare the oxidative metabolism of (S)-mephenytoin and proguanil in vitro and to determine the involvement of various cytochrome P450 isoforms. (Comparative Study)
Comparative Study
AIMS
To compare the oxidative metabolism of (S)-mephenytoin and proguanil in vitro and to determine the involvement of various cytochrome P450 isoforms.
METHODS
The kinetics of the formation of 4'-hydroxymephenytoin and cycloguanil in human liver microsomes from 10 liver samples were determined, and inhibition of formation was studied using specific chemical inhibitors and monoclonal antibodies directed towards specific CYP450 isoforms. Expressed CYP450 enzymes were used to characterize further CYP isoform contribution in vitro. Livers were genotyped for CYP2C19 using PCR amplification of genomic DNA followed by restriction endonuclease digestion.
RESULTS
All livers were wildtype with respect to CYP2C19, except HLS#5 whose genotype was CYP2C19*1/CYP2C19*2. The Km, Vmax and CLint values for the formation of 4'-hydroxymephenytoin from (S)-mephenytoin and the formation of cycloguanil from proguanil ranged from 50.8 to 51.6 and 43-380 microm, 1.0-13.9 and 0.5-2.5 nmol mg-1 h-1, and 20.2-273.8 and 2.7-38.9 microl h-1 mg-1, respectively. There was a significant association between the Vmax values of cycloguanil and 4'-hydroxymephenytoin formation (rs=0.95, P=0.0004). Cycloguanil formation was inhibited significantly by omeprazole (CYP2C19/3A), troleandomycin (CYP3A), diethyldithiocarbamate (CYP2E1/3A), furafylline (CYP1A2), and (S)-mephenytoin. 4'-Hydroxymephenytoin formation was inhibited significantly by omeprazole, diethyldithiocarbamate, proguanil, furafylline, diazepam, troleandomycin, and sulphaphenazole (CYP2C9). Human CYP2E1 and CYP3A4 monoclonal antibodies did not inhibit the formation of cycloguanil or 4'-hydroxymephenytoin, and cycloguanil was formed by expressed CYP3A4 and CYP2C19 supersomes. However, only expressed CYP2C19 and CYP2C19 supersomes formed 4'-hydroxymephenytoin.
CONCLUSIONS
The oxidative metabolism of (S)-mephenytoin and proguanil in vitro is catalysed by CYPs 2C19 and 1A2, with the significant association between Vmax values suggesting that the predominant enzymes involved in both reactions are similar. However the degree of selectively of both drugs for CYP isoforms needs further investigation, particularly the involvement of CYP3A4 in the metabolism of proguanil. We assert that proguanil may not be a suitable alternative to (S)-mephenytoin as a probe drug for the CYP2C19 genetic polymorphism.
Topics: Adult; Aged; Antibodies, Monoclonal; Anticonvulsants; Antimetabolites; Cytochrome P-450 Enzyme System; Enzyme Inhibitors; Female; Folic Acid Antagonists; Genotype; Humans; In Vitro Techniques; Isoenzymes; Male; Mephenytoin; Microsomes, Liver; Middle Aged; Oxidation-Reduction; Proguanil; Triazines
PubMed: 10417492
DOI: 10.1046/j.1365-2125.1999.00005.x