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1.
1.?The identification and relative contributions of human cytochrome P450 (CYP) enzymes involved in the metabolism of glibenclamide and lansoprazole in human liver microsomes were investigated using an approach based on the in vitro disappearance rate of unchanged drug.2.?Recombinant CYP2C19 and CYP3A4 catalysed a significant disappearance of both drugs. When the contribution of CYPs to the intrinsic clearance (CL int) of drugs in pooled human microsomes was estimated by relative activity factors, contributions of CYP2C19 and CYP3A4 were determined to be 4.6 and 96.4% for glibenclamide, and 75.1 and 35.6% for lansoprazole, respectively.3.?CL int of glibenclamide correlated very well with CYP3A4 marker activity, whereas the CL int of lansoprazole significantly correlated with CYP2C19 and CYP3A4 marker activities in human liver microsomes from 12 separate individuals. Effects of CYP-specific inhibitors and anti-CYP3A serum on the CL int of drugs in pooled human liver microsomes reflected the relative contributions of CYP2C19 and CYP3A4.4.?The results suggest that glibenclamide is mainly metabolized by CYP3A4, whereas lansoprazole is metabolized by both CYP2C19 and CYP3A4 in human liver microsomes. This approach, based on the in vitro drug disappearance rate, is useful for estimating CYP identification and their contribution to drug discovery. 相似文献
2.
Rats with liver cirrhosis induced by N‐dimethylnitrosamine (LC) and rats with LC with diabetes mellitus induced by streptozotocin (LCD) have been developed as animal models for human liver cirrhosis and liver cirrhosis with diabetes mellitus, respectively. Changes in the pharmacokinetics of drugs (mainly non‐renal clearance, CLNR) in LC and LCD rats reported in the literature compared with respective control rats were reviewed. This review mainly explains the changes in the CLNRs of drugs (which are mainly metabolized via hepatic microsomal cytochrome P450s, CYPs) in LC and LCD rats, in terms of the changes in in vitro hepatic intrinsic clearance ( CLint; mainly due to the changes in CYPs in the disease state), free (unbound) fraction of a drug in the plasma ( fp) and hepatic blood flow rate ( QH) depending on the hepatic excretion ratio of the drug. Generally, changes in the CLNRs of drugs in LC and LCD rats could be well explained by the above‐mentioned three factors. The mechanism of urinary excretion of drugs (such as glomerular filtration or renal active secretion or reabsorption) in LC and LCD rats is also discussed. The pharmacokinetics of the drugs reported in the LC and LCD rats were scarce in humans. Thus, the present rat data should be extrapolated carefully to humans. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
3.
A total of 110 drugs, selected to cover a range of physicochemical and pharmacokinetic properties, were used to explore standard approaches to the prediction of in vivo metabolic clearance using drug-depletion profiles from human liver microsomes (HLMs) and cyropreserved hepatocytes. A total of 41 drugs (37% of the compounds tested) showed measurable depletion rates using HLMs (depletion by 20% or more over the time course). The most reliable correlations in terms of bias (average fold error (AFE) = 2.32) and precision (root mean square error (RMSE) = 3501) were observed by comparing in vivo intrinsic clearance (CL int), calculated using the parallel-tube model and incorporating the fraction unbound in blood, with in vitro CL int adjusted for microsomal binding. For these reference drugs, 29% of predictions were within two-fold of the observed values and 66% were within five-fold. Compared with HLMs, clearance predictions with cryopreserved hepatocytes (57 drugs) were of similar precision (RMSE = 3608) but showed more bias (AFE = 5.21) with 18% of predictions within two-fold of the observed values and 46% within five-fold. However, with a broad complement of drug-metabolizing enzymes, hepatocytes catalysed measurable CL int values for a greater proportion (52%) of the reference compounds and were particularly proficient at defining metabolic rates for drugs with predominantly phase 2 metabolic routes. 相似文献
4.
Various pharmacokinetic parameters—disposition half-life, t
1/2,z, metabolic clearance CL m, volume of distribution V, intrinsic clearance of unbound drug CLu t, and unbound volume of distribution of tissues (distributive tissue volume / fraction of drug in tissue unbound, V T/fu T—are compared in rat and human for nine weakly acidic drugs, phenytoin, hexobarbital, pentobarbital, phenylbutazone, warfarin, tolbutamide, valproate, phenobarbital, and amobarbital, and six weakly basic drugs, quinidine, chlorpromazine, propranolol, pentazocin, antipyrine, and diazepam. With regard to all parameters, statistically significant correlations are obtained when parameters are plotted on a log-log plot. Correlation coefficients between the intrinsic parameters (CLu int or V T/fu T) were higher than those between the hybrid parameters (t 1/2,z, CL m, or V). In general, these drugs were metabolized ten times more rapidly in rat than in human. With regard to the tissue distribution of these drugs, there was little difference between rat and human. Predictions of CL m, V, and t 1/2, in humans using rat data were successful for most drugs, with a few marked exceptions. 相似文献
5.
In order to evaluate the potential adverse effects due to genetic polymorphism and/or inter-individual variation, it is necessary to calculate the cytochrome P450 (CYP) contribution to the metabolism of new drugs. In the current study, the in vitro intrinsic clearance (CL int) values of marker substrates and drugs were determined by measuring metabolite formation and substrate depletion, respectively. Recombinant CYP microsomes expressing CYP2C9, CYP2C19 and CYP3A4 with co-expressed cytochrome b5 were used, but those expressing CYP1A2 and CYP2D6 did not have co-expressed cytochrome b5. The following prediction methods were compared to determine the CL int value using data from recombinant CYP enzymes: (1) relative CYP enzyme content in human liver microsomes; (2) relative activity factor (RAF) estimated from the Vmax value; and (3) RAF estimated from the CL int value. Estimating RAF from CL int proved the most accurate prediction method among the three tested, and differences in the CYP3A4 marker reactions did not affect its accuracy. The substrate depletion method will be useful in the early drug-discovery stage when the main metabolite and/or metabolic pathway has not been identified. In addition, recombinant CYP microsomes co-expressed with cytochrome b5 might be suitable for the prediction of the CL int value. 相似文献
6.
We previously reported that the accuracy of clearance (CL) prediction could be differentiated by permeability. CL was drastically under-predicted by in vitro metabolic intrinsic clearance (CLint) for compounds with low permeability (<5?×?10?6 cm/s). We determined apparent uptake CLint by measuring initial disappearance from medium using attached rat hepatocytes and metabolic CLint by measuring parent depletion in suspended rat hepatocytes (cells and medium). Uptake and metabolic CLint were comparable for highly permeable metabolic marker compounds. In contrast, uptake CLint was 3- to 40-fold higher than metabolic CLint for rosuvastatin, bosentan, and 15 proprietary compounds, which had low permeability, suggesting that uptake could be a rate-determining step in hepatic elimination for these poorly permeable compounds. The prediction of hepatic CL was improved significantly when using uptake CLint for the compounds with low permeability. The average fold error was 2.2 and 6, as opposed to >11 and >47 by metabolic CLint, with and without applying a scaling factor of 4, respectively. Uptake CLint from attached hepatocytes can be used as an alternative approach to predict hepatic clearance and to understand the significance of hepatic uptake in elimination in an early drug discovery setting. 相似文献
7.
To evaluate the role that cytochrome (CYP) 3A5 plays in hepatic drug metabolism, the substrate selectivity and inhibitory potential of over 60 compounds towards CYP3A4 and CYP3A5 were assessed using Escherichia coli recombinant cell lines. CYP3A4-mediated metabolism predominated for many of the compounds studied. However, a number of drugs gave similar CL int estimates using CYP3A5 compared with CYP3A4 including midazolam (CL int?=?3.4 versus 3.3?µl?min –1?pmol –1). Significant CYP3A5-mediated metabolism was also observed for several drugs including mifepristone (CL int?=?10.3 versus 2.4?µl?min –1?pmol –1), and ritonavir (CL int?=?0.76 versus 0.47?µl?min –1?pmol –1). The majority of compounds studied showed a greater inhibitory potential (IC 50) towards CYP3A4 compared with CYP3A5 (eightfold lower on average). A greater degree of time-dependent inhibition was also observed with CYP3A4 compared with CYP3A5. The range of compounds investigated in the present study extends significantly previous work and suggests that CYP3A5 may have a significant role in drug metabolism particularly in populations expressing high levels of CYP3A5 and/or on co-medications known to inhibit CYP3A4. 相似文献
8.
No HeadingPurpose. The aim of this study is to compare the accuracy of five methods for predicting in vivo intrinsic clearance (CL int) and seven for predicting hepatic clearance (CL h) in humans using in vitro microsomal data and/or preclinical animal data.Methods. The human CL int was predicted for 33 drugs by five methods that used either in vitro data with a physiologic scaling factor (SF), with an empirical SF, with the physiologic and drug-specific (the ratio of in vivo and in vitro CL int in rats) SFs, or rat CL int directly and with allometric scaling. Using the estimated CL int, the CL h in humans was calculated according to the well-stirred liver model. The CL h was also predicted using additional two methods: using direct allometric scaling or drug-specific SF and allometry.Results. Using in vitro human microsomal data with a physiologic SF resulted in consistent underestimation of both CL int and CL h . This bias was reduced by using either an empirical SF, a drug-specific SF, or allometry. However, for allometry, there was a substantial decrease in precision. For drug-specific SF, bias was less reduced, precision was similar to an empirical SF. Both CL int and CL h were best predicted using in vitro human microsomal data with empirical SF. Use of larger data set of 52 drugs with the well-stirred liver model resulted in a best-fit empirical SF that is 9-fold increase on the physiologic SF.Conclusions. Overall, the empirical SF method and the drug-specific SF method appear to be the best methods; they show lower bias than the physiologic SF and better precision than allometric approaches. The use of in vitro human microsomal data with an empirical SF may be preferable, as it does not require extra information from a preclinical study. 相似文献
9.
Oxidative deamination of the GABAA partial agonist CP-409,092 and sumatriptan represents a major metabolic pathway and seems to play an important role for the clearance of these two compounds. Similar to sumatriptan, human mitochondrial incubations with deprenyl and clorgyline, probe inhibitors of monoamine oxidase B and monoamine oxidase A (MAO-B and MAO-A), respectively, showed that CP-409,092 was metabolized to a large extent by the enzyme MAO-A. The metabolism of CP-409,092 and sumatriptan was therefore studied in human liver mitochondria and in vitro intrinsic clearance (CLint) values were determined and compared to the corresponding in vivo oral clearance (CLPO) values. The overall objective was to determine whether an in vitro-in vivo correlation (IVIVC) could be described for compounds cleared by MAO-A. The intrinsic clearance, CLint, of CP-409,092 was approximately 4-fold greater than that of sumatriptan (CLint, values were calculated as 0.008 and 0.002?ml/mg/min for CP-409,092 and sumatriptan, respectively). A similar correlation was observed from the in vivo metabolic data where the unbound oral clearance, CL(u)PO, values in humans were calculated as 724 and 178?ml/min/kg for CP-409,092 and sumatriptan, respectively. The present work demonstrates that it is possible to predict in vivo metabolic clearance from in vitro metabolic data for drugs metabolized by the enzyme monoamine oxidase. 相似文献
10.
The effect of acute renal failure (ARF) on the pharmacokinetics of sulfobromophthalein (BSP) was investigated in order to
elucidate if renal failure modifies the hepatic metabolism of drugs. ARF was induced by intravenous ( iv) injection of uranyl nitrate (UN) to rats (5 mg/kg) five days before the experiment. Area under the plasma concentration-time
curve ( AUC) of BSP after portal vein ( pv) injection increased by 2-fold and total body clearance ( CL
t) decreased one half (p<0.01) in UN-induced ARF (UN-ARF) rats compared to the control rats. But the plasma disappearance of
BSP after iv injection did not differ significantly between control and UN-ARF rats. Since BSP is excreted via the liver, CL
t representd the approximate hepatic clearance of BSP. Therefore, the decrease in CL
t represents a decrease in hepatic intrinsic clearance ( CL
int) for BSP since plasma free fraction ( f
p) of BSP was not affected by UN-ARF. The content of hepatic cytoplasmic Y-protein, which catalyzes BSP-glutathione conjugation
and limits the transfer of BSP from blood to bile, increased significantly (p<0.01), however its binding activity (BA) for
BSP was decreased significantly (p<0.01) by UN-ARF. The decrease in CL
int might have some correlation with the changed characteristics of hepatic Y-protein, specifically its decreased BA for BSP. 相似文献
11.
It is important to determine the cytochrome P450 (CYP) contribution of certain drugs by taking into consideration the attrition due to issues such as genetic polymorphism and inter-individual variation. In many cases in the early discovery stage, the metabolites of a new chemical have not been identified. Therefore, the present paper devised an approach in which the in vitro intrinsic clearance (CL int) value for new chemicals was determined by measuring substrate depletion. The following prediction methods were compared to calculate CL int using data from recombinant CYP enzymes: (1) the relative CYP content in human liver microsomes; (2) the relative activity factor (RAF) based on the Vmax value; and (3) the RAF value based on the CL int value. The most accurate prediction method was RAF based on CL int. This method would be useful in the early drug-discovery process in cases in which the main metabolite is not identified. 相似文献
13.
Purpose To assess the extent of intestinal and hepatic glucuronidation in vitro and resulting implications on glucuronidation clearance prediction.
Methods Alamethicin activated human intestinal (HIM) and hepatic (HLM) microsomes were used to obtain intrinsic glucuronidation clearance
(CL int,UGT) for nine drugs using substrate depletion. The in vitro extent of glucuronidation (fm UGT) was determined using P450 and UGT cofactors. Utility of hepatic CL int for the prediction of in vivo clearance was assessed.
Results fm UGT (8–100%) was comparable between HLM and HIM with the exception of troglitazone, where a nine-fold difference was observed
(8% and 74%, respectively). Scaled intestinal CL int,UGT (per g tissue) was six- and nine-fold higher than hepatic for raloxifene and troglitazone, respectively, and comparable to
hepatic for naloxone. The remaining drugs had a higher hepatic than intestinal CL int,UGT (average five-fold). For all drugs with P450 clearance, hepatic CL int,CYP was higher than intestinal (average 15-fold). Hepatic CL int,UGT predicted on average 22% of observed in vivo CL int; with the exception of raloxifene and troglitazone, where the prediction was only 3%.
Conclusion Intestinal glucuronidation should be incorporated into clearance prediction, especially for compounds metabolised by intestine
specific UGTs. Alamethicin activated microsomes are useful for the assessment of intestinal glucuronidation and fm UGT
in vitro. 相似文献
14.
1.?The purpose of this study was to evaluate drug clearance measured by the metabolic intrinsic clearance (CL int) in a substrate depletion assay in comparison with the in vivo clearance (CL tot) observed in adjuvant-induced arthritis (AA) rats. 2.?After intravenous administration of diclofenac as a model drug, CL tot was 2.8-fold higher in AA rats than in control rats. In two different substrate depletion assays with liver microsomes for glucuronidation and hydroxylation, the CL int values for glucuronidation was significantly decreased in AA rats to 60% of the value in control rats, whereas the CL int values for hydroxylation were similar. The unbound fraction of diclofenac in plasma ( fu, plasma) was significantly higher (2.8-fold) in AA rats than in control rats. 3.?Hepatic clearance predicted from the CL int values for both biotransformation pathways and fu, plasma was higher in AA rats than in control rats, with good consistency between predicted and observed values. The same results were obtained for experiments using hepatocytes. 4.?The plasma protein-binding activities, rather than metabolic clearance, in both types of rats would be a determining factor in the pharmacokinetic behaviour differences between control and AA rats. 5.?In summary, substrate depletion assays with liver microsomes and hepatocytes in combination with protein binding assessment can help to predict changes in pharmacokinetics under AA conditions. 相似文献
15.
This study was initiated to characterize the metabolism and pharmacokinetics of SNC80 in rats and to evaluate the impact of Freund's complete adjuvant (FCA)-induced inflammation on its body disposition. In vitro, the disappearance and intrinsic clearance (CL int) of SNC80 were measured following incubations in recombinant rat CYPs and in phenotyped liver microsomes from naive and 24-h FCA-treated rats. The unbound fraction (f u) was assessed by ultrafiltration. Based on the Clint values, in vivo blood clearance of 3.35 and 2.48 L/h/kg were predicted in naive and FCA-treated rats. In vivo, SNC80 was administered to naive and 24-h FCA-treated rats at 10?µmol/kg i.v. and 50?µmol/kg p.o. The naive animals showed high plasma clearance (3.1 L/h/kg), low renal clearance (<0.02 L/h/kg) and poor bioavailability (<4%). Following i.v. administration, plasma clearance was lower (22%) in FCA-treated vs. untreated rats. Despite the decreases in f u (~30%) and CL int (~40%) in vitro, in vivo the apparent bioavailability and oral clearance were not significantly different between FCA-treated and naive rats. Hepatic and possibly intestinal losses contribute to the low bioavailability of SNC80. Non-hepatic mechanisms may compensate for the decrease in plasma clearance found in FCA-treated rats, preventing an increase in the oral bioavailability of SNC80. 相似文献
16.
1. Plasma lipid profile abnormalities in hyperlipidemia can potentially alter the pharmacokinetics of a drug in a complex manner. To evaluate these pharmacokinetic alterations in hyperlipidemia and to determine the underlying mechanism(s), poloxamer 407-induced hyperlipidemic rats (HL rats), a well-established animal model of hyperlipidemia have been used. 2. In this review, we summarize findings on the pathophysiological and gene expression changes in drug-metabolizing enzymes and transporters in HL rats. We discuss pharmacokinetic changes in drugs metabolized primarily via hepatic cytochrome P450 (CYPs) in terms of alterations in hepatic intrinsic clearance (CL′int), free fraction in plasma (fu) and hepatic blood flow rate (QH), depending on the hepatic excretion ratio, as well as drugs eliminated primarily by mechanisms other than hepatic CYPs. 3. For lipoprotein-bound drugs, increased binding to lipoproteins resulted in lower fu values and volumes of distribution, with some exceptions. Generally, slower non-renal clearance (or total body clearance) of drugs that are substrates of hepatic CYP3A and CYP2C is well explained by the following factors: alterations in CL′int (due to down-regulation of hepatic CYPs), decreased fu and/or possible decreased QH. 4. These consistent findings across studies in HL rats suggest more studies are needed at the clinical level for optimal pharmacotherapies for hyperlipidemia. 相似文献
17.
Purpose. The membrane permeability clearance and intrinsic metabolic clearance of a drug in the liver were estimated using isolated rat hepatocytes, and the rate-limiting step in the overall intrinsic clearance of the drug in vivo was investigated. For this purpose, an anti-dementia drug, (S)-(-)-2,8-dimethyl-3-methylene-l-oxa-8-azaspiro [4,5] de-cane-L-tartarate monohydrate (YM796) was used as a model drug.
Methods. The parent drug and its metabolites in both medium and cells were separated by thin-layer chromatography (TLC). The total amount of drug taken up by hepatocytes and the total amount of metabolites were plotted against the AUC of YM796 in the medium or cells to obtain the kinetic parameters.
Results. While the influx clearance (PS int) through the sinusoidal membrane defined in terms of YM796 concentration in the medium was almost constant, irrespective of the concentration of YM796 in the medium, the intrinsic metabolic clearance (CL int) and the efflux clearance (PS eff) defined in terms of the total concentration of YM796 in the cells markedly decreased and increased, respectively, as the concentration of YM796 increased. The overall intrinsic metabolic clearance (Cl int,all), defined in terms of the YM796 concentration in the medium, corresponding to the hepatic intrinsic clearance obtained from the in vivo pharmacokinetic data on the drug, was comparable with PS inf at low concentrations of YM796. As the YM796 concentration increased, however, Cl int,all fell markedly approaching CL int.
Conclusions. While, at low concentrations of YM796, CL int,all was predominantly affected by membrane permeability clearance, at high concentrations it was completely rate-determined by the intrinsic metabolic clearance because of the marked reduction in CL int resulting from the saturation of YM796 metabolism. 相似文献
18.
1.?Failure to predict human pharmacokinetics of aldehyde oxidase (AO) substrates using traditional allometry has been attributed to species differences in AO metabolism.2.?To identify appropriate species for predicting human in vivo clearance by single-species scaling (SSS) or multispecies allometry (MA), we scaled in vitro intrinsic clearance (CL int) of five AO substrates obtained from hepatic S9 of mouse, rat, guinea pig, monkey and minipig to human in vitro CL int.3.?When predicting human in vitro CL int, average absolute fold-error was ≤2.0 by SSS with monkey, minipig and guinea pig (rat/mouse >3.0) and was <3.0 by most MA species combinations (including rat/mouse combinations).4.?Interspecies variables, including fraction metabolized by AO (F m,AO) and hepatic extraction ratios (E) were estimated in vitro. SSS prediction fold-errors correlated with the animal:human ratio of E ( r2?=?0.6488), but not F m,AO ( r2?=?0.0051).5.?Using plasma clearance (CL p) from the literature, SSS with monkey was superior to rat or mouse at predicting human CL p of BIBX1382 and zoniporide, consistent with in vitro SSS assessments.6.?Evaluation of in vitro allometry, F m,AO and E may prove useful to guide selection of suitable species for traditional allometry and prediction of human pharmacokinetics of AO substrates. 相似文献
19.
Objective: The purposes of this study were to identify the P450 enzyme (CYP) responsible for zonisamide metabolism in humans by using
expressed human CYPs and to predict drug interaction of zonisamide in vivo from in vitro data. Methods: Ten expressed human CYPs and human liver microsomes were used in the experiments for the identification of enzymes responsible
for zonisamide metabolism and for the prediction of drug-drug interactions of zonisamide metabolism in humans from in vitro
data, respectively. Two-sulfamoylacetyl phenol, a reductive metabolite of zonisamide, was measured by the HPLC method. Results: From the experiments using ten expressed human CYPs, CYP2C19, CYP3A4 and CYP3A5 were shown to be capable of catalyzing zonisamide
reduction. However, an intrinsic clearance, V max/k M, of CYP3A4 was much higher than those of CYP2C19 and CYP3A5. From the point of view of enzyme amount in human liver CYPs
isoform and their intrinsic clearance, it was suggested that CYP3A4 is mainly responsible for zonisamide metabolism in human
CYPs. Zonisamide metabolism in human liver microsomes was markedly inhibited by cyclosporin A, dihydroergotamine, ketoconazole,
itraconazole, miconazole and triazolam. We estimated the possibility and degree of change of zonisamide clearance in vivo
in clinical dose range from in vitro inhibition constant of other drugs against zonisamide metabolism (Ki) and unbound inhibitor
concentration in blood (Iu) in clinical usage. Clearance of zonisamide was maximally estimated to decrease by 31%, 23% and
17% of the clearance without inhibitors i.e. ketoconazole, cyclospolin A and miconazole, respectively. Fluconazole and carbamazepine
are estimated to decrease by 5–6% of the clearance of zonisamide. On the other hand, there may be lack of interaction of zonisamide
metabolism by dihydroergotamine, itraconazole and triazolam in clinical dose range. Conclusion: We demonstrated that: (1) zonisamide is metabolized by recombinant CYP3A4, CYP2C19 and CYP3A5, (2) the metabolism is inhibited
to a variable extent by known CYP3A4/5 substrates and/or inhibitors in human liver microsomes, and (3) in vitro-in vivo predictive
calculations suggest that several compounds demonstrating CYP3A4-affinity might cause in vivo drug-drug interactions with
zonisamide.
Received: 12 June 1997 / Accepted in revised form: 17 November 1997 相似文献
20.
Abstract1. Prediction of human pharmacokinetics might be made more precise by using species with similar metabolic activities to humans. We had previously reported the species differences in intestinal and hepatic metabolic activities of 43 cytochrome P450 (CYP) substrates between cynomolgus monkeys and humans. However, the species differences between humans and rats or dogs had not yet been determined using comparable data sets with sufficient number of compounds.2. Here, we investigated metabolic stabilities in intestinal and liver microsomes obtained from rats, dogs and humans using 43 substrates of human CYP1A2, CYP2J2, CYP2C, CYP2D6 and CYP3A.3. Hepatic intrinsic clearance ( CLint) values for most compounds in dogs were comparable to those in humans (within 10-fold), whereas in rats, those for the human CYP2D6 substrates were much higher and showed low correlation with humans. In dog intestine, as with human intestine, CLint values for almost all human CYP1A2, CYP2C, CYP2D6 substrates were not determined because they were very low. Intestinal CLint values for human CYP3A substrates in rats and dogs appeared to be lower for most of the compounds and showed moderate correlation with those in humans.4. In conclusion, dogs showed the most similar metabolic activity to humans. 相似文献
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