RT Journal Article
SR Electronic
T1 Current Cytochrome P450 Phenotyping Methods Applied to Metabolic Drug-Drug Interaction Prediction in Dogs
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 396
OP 404
DO 10.1124/dmd.109.030429
VO 38
IS 3
A1 Mills, Beth Miskimins
A1 Zaya, Matthew J.
A1 Walters, Rodney R.
A1 Feenstra, Kenneth L.
A1 White, Julie A.
A1 Gagne, Jason
A1 Locuson, Charles W.
YR 2010
UL http://dmd.aspetjournals.org/content/38/3/396.abstract
AB Recombinant cytochrome P450 (P450) phenotyping, different approaches for estimating fraction metabolized (fm), and multiple measures of in vivo inhibitor exposure were tested for their ability to predict drug interaction magnitude in dogs. In previous reports, midazolam-ketoconazole interaction studies in dogs have been attributed to inhibition of CYP3A pathways. However, in vitro phenotyping studies demonstrated higher apparent intrinsic clearances (CLint,app) of midazolam with canine CYP2B11 and CYP2C21. Application of activity correction factors and isoform hepatic abundance to liver microsome CLint,app values further implicated CYP2B11 (fm ≥ 0.89) as the dog enzyme responsible for midazolam- and temazepam-ketoconazole interactions in vivo. Mean area under the curve (AUC) in the presence of the inhibitor/AUC ratios from intravenous and oral midazolam interaction studies were predicted well with unbound Ki and estimates of unbound hepatic inlet inhibitor concentrations and intestinal metabolism using the AUC-competitive inhibitor relationship. No interactions were observed in vivo with bufuralol, although significant interactions with bufuralol were predicted with fluoxetine via CYP2D and CYP2C pathways (>2.45-fold) but not with clomipramine (<2-fold). The minor caffeine-fluvoxamine interaction (1.78-fold) was slightly higher than predicted values based on determination of a moderate fm value for CYP1A1, although CYP1A2 may also be involved in caffeine metabolism. The findings suggest promise for in vitro approaches to drug interaction assessment in dogs, but they also highlight the need to identify improved substrate and inhibitor probes for canine P450s. Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics