![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
|
|
|
|
|
||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Received for publication May 3, 2005.
Revised September 15, 2005.
Accepted for publication September 16, 2005.
Abstract Predictions of intrinsic clearance (CLint) from human liver microsomes often underestimate in vivo observations. In this study, a series of five benzodiazepines were used as prototypic CYP3A4 substrates in order to investigate the prediction of clearance from the less studied alternative in vitro system, cryopreserved human hepatocytes. Formation of the two major metabolites from midazolam, triazolam, diazepam, flunitrazepam and alprazolam was measured in cryopreserved human hepatocytes from five donors; the kinetics were characterised and CLint values determined and scaled to predict CLint in vivo. At least one of the two major pathways of metabolic clearance of each benzodiazepine was characterised by autoactivation in hepatocytes; the extent to which this occurred varied depending on substrate and liver (up to 8-fold). Heteroactivation by testosterone of these pathways was also observed (up to 6-fold). The maximum autoactivated clearance was used to predict in vivo CLint (1.6 - 138ml/min/kg) which closely agreed with values previously obtained using human liver microsomes. Comparison with in vivo CLint indicates that cryopreserved human hepatocytes systematically under-predict CLint. When three previous studies (documenting CLint for substrates of various enzymes in cryopreserved human hepatocytes using drug depletion-time profiles) were considered as well, the combined data show a consistent underprediction of 5.6-fold. Collectively it is demonstrated that the predicted hepatic intrinsic clearances from cryopreserved hepatocytes show an excellent rank order with in vivo findings but are systematically under-predicting the in vivo value.
Key words:
drug clearance, enzyme kinetics, hepatic elimination, hepatocytes, human CYP enzymes, in vitro-in vivo prediction, in vitro-in vivo scaling
This article has been cited by other articles:
|
|
 |
|
  J. B. Dennison, M. A. Mohutsky, R. J. Barbuch, S. A. Wrighton, and S. D. Hall Apparent High CYP3A5 Expression Is Required for Significant Metabolism of Vincristine by Human Cryopreserved Hepatocytes J. Pharmacol. Exp. Ther., October 1, 2008; 327(1): 248 - 257. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. J. Parker and J. B. Houston Rate-Limiting Steps in Hepatic Drug Clearance: Comparison of Hepatocellular Uptake and Metabolism with Microsomal Metabolism of Saquinavir, Nelfinavir, and Ritonavir Drug Metab. Dispos., July 1, 2008; 36(7): 1375 - 1384. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. S. Brown, A. Chadwick, and J. B. Houston Use of Isolated Hepatocyte Preparations for Cytochrome P450 Inhibition Studies: Comparison with Microsomes for Ki Determination Drug Metab. Dispos., November 1, 2007; 35(11): 2119 - 2126. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Hallifax and J. B. Houston Saturable Uptake of Lipophilic Amine Drugs into Isolated Hepatocytes: Mechanisms and Consequences for Quantitative Clearance Prediction Drug Metab. Dispos., August 1, 2007; 35(8): 1325 - 1332. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. S. Brown, M. Griffin, and J. B. Houston Evaluation of Cryopreserved Human Hepatocytes as an Alternative in Vitro System to Microsomes for the Prediction of Metabolic Clearance Drug Metab. Dispos., February 1, 2007; 35(2): 293 - 301. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Hallifax and J. B. Houston Uptake and Intracellular Binding of Lipophilic Amine Drugs by Isolated Rat Hepatocytes and Implications for Prediction of in Vivo Metabolic Clearance Drug Metab. Dispos., November 1, 2006; 34(11): 1829 - 1836. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Lu, P. Li, R. Gallegos, V. Uttamsingh, C. Q. Xia, G. T. Miwa, S. K. Balani, and L.-S. Gan Comparison of Intrinsic Clearance in Liver Microsomes and Hepatocytes from Rats and Humans: Evaluation of Free Fraction and Uptake in Hepatocytes Drug Metab. Dispos., September 1, 2006; 34(9): 1600 - 1605. [Abstract] [Full Text] [PDF]
|
|
 |
 |
 |
|
 |
 |
 |
