title: Development of an in vitro incubation procedure for screening of CYP2D6 intrinsic clearance.
abstract: The in vitro intrinsic clearances (CL(int)) for the metabolism of p-methoxymethamphetamine (PMMA) and fluoxetine by the CYP2D6 enzyme were calculated using a steady-state (SS) approach and a new general enzyme (GE) method, which measures the formation of product and the depletion of substrate as a function of time. For PMMA, the SS experiment resulted in a CL(int) of 2.7+/-0.2 microL pmol 2D6(-1)min(-1) and the GE experiment resulted in a CL(int) of 3.0+/-0.6 microL pmol 2D6(-1)min(-1). For fluoxetine, the SS experiment resulted in a CL(int) of 0.33+/-0.17 microL pmol 2D6(-1)min(-1) and the GE experiment resulted in a CL(int) of 0.188+/-0.013 microL pmol 2D6(-1)min(-1). We used two kinetic modeling techniques that can accommodate atypical kinetic models. We also show that the addition of fluoxetine results in a 10-fold decrease in the observed intrinsic clearance of PMMA, confirming that fluoxetine is a potent inhibitor of the liver enzyme CYP2D6.
authors.affiliation: Virginia Commonwealth University, Department of Chemistry, 1001 W. Main Street, Box 842006, Richmond, VA 23284-2006, USA.
authors.forename: Sarah E G
authors.initials: SE
authors.lastname: Porter
authors.forename: Richard B
authors.initials: RB
authors.lastname: Keithley
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Rutan
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism*; D005473:Fluoxetine / Q000494:pharmacology; D007700:Kinetics; D008694:Methamphetamine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics; D012015:Reference Standards; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
chemical_list: D005473:Fluoxetine; D008694:Methamphetamine; D019389:Cytochrome P-450 CYP2D6