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In Vitro / in Vivo scaling of alprazolam metabolism by CYP3A4 and CYP3A5 in humans
Author(s) -
Hirota Noriko,
Ito Kiyomi,
Iwatsubo Takafumi,
Green Carol E.,
Tyson Charles A.,
Shimada Noriaki,
Suzuki Hiroshi,
Sugiyama Yuichi
Publication year - 2001
Publication title -
biopharmaceutics and drug disposition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.419
H-Index - 58
eISSN - 1099-081X
pISSN - 0142-2782
DOI - 10.1002/bdd.261
Subject(s) - microsome , cyp3a4 , hydroxylation , in vivo , chemistry , cytochrome p450 , metabolism , pharmacokinetics , pharmacology , in vitro , endocrinology , biology , biochemistry , enzyme , microbiology and biotechnology
We attempted to predict the in vivo metabolic clearance of alprazolam from in vitro metabolic studies using human liver microsomes and human CYP recombinants. Good correlations were observed between the intrinsic clearance (CL int ) for 4‐hydroxylation and CYP3A4 content and between the CL int for α‐hydroxylation and CYP3A5 content in ten human liver microsomal samples. Using the recombinant CYP isoforms expressed in insect cells, the CL int for CYP3A4 was about 2‐fold higher than the CL int for CYP3A5 in the case of 4‐hydroxylation. However, the CL int for CYP3A5 was about 3‐fold higher than the CL int for CYP3A4 in the case of α‐hydroxylation. The metabolic rates for 4‐ and α‐hydroxylation increased as the added amount of cytochrome b 5 increased, and their maximum values were 3‐ to 4‐fold higher than those without cytochrome b 5 . The values of CL int , in vivo predicted from in vitro studies using human liver microsomes and CYP3A4 and CYP3A5 recombinants were within 2.5 times of the observed value calculated from literature data. The average CL int value (sum of 4‐ and α‐hydroxylation) obtained using three human liver microsomal samples was 4‐fold higher than that obtained using three small intestinal microsomal samples from the same donors, indicating the minor contribution of intestinal metabolism to alprazolam disposition. The area under the plasma concentration‐time curve (AUC) of alprazolam is reported to increase following co‐administration of ketoconazole and the magnitude of the increase predicted from the in vitro K i values and reported pharmacokinetic parameters of ketoconazole was 2.30–2.45, which is close to the value observed in vivo (3.19). A quantitative prediction of the AUC increase by cimetidine was also successful (1.73–1.79 vs 1.58–1.64), considering the active transport of cimetidine into the liver. In conclusion, we have succeeded in carrying out an in vitro / in vivo scaling of alprazolam metabolism using human liver microsomes and human CYP3A4 and CYP3A5 recombinants. Copyright © 2001 John Wiley & Sons, Ltd.