Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy 52 Pharmacodynamics of Enzyme Induction and its Consequences for Substrate Elimination MATS O. MAGNUSSON ACTA UNIVERSITATIS UPSALIENSIS ISSN 1651-6192 UPPSALA ISBN 978-91-554-6860-6 2007 urn:nbn:se:uu:diva-7812 ! "##$ %& ' ( ) ' ' *( ( +! ' *( ,- .( (- ) /- "##$- *( ' 0 1 2 3 ' 0 - 4 - &"- 5" - - 26 7$8979&&9585#95- 0 1 ( ( ( ' 1-2' ( '' 1 ( ' ) ( ) - 2 (' ' : ) ) - .( ( ( '9' ' ( 1 ( ( ; ' ( ) ) ( ( ( < ( - .( ' ( ( ) ( ; ' 1 ( 3 ( ( ' - ' ) ' ( ( ' ( ' ( ' ( - 0 1 ( 1 ) ( ( (- 4 ) ( ( ) ( ( ; ' ( 1 6=49$& ( 1 - .( 3 ' ( ) ( ( ; ) ) ' 9 ( ) ( ' ( ) ) ' - .( ' ( ) - 2 ( ' ' ( ( ( ; ' ( ) ) ( '' 1 - .( ( ) ) ( ) 1 ( - 2 ( ' ) ( ' ( 1 ( ( ( 1 - .( ) ( ( '9 ' >*%4 >*4" - .( ; ' ( 1 ( ) ( - .( ( ) ' ( 3 ' - *( ; *( 0 1 . . 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A mechanism- based integrated pharmacokinetic enzyme model describing the time course and magnitude of phenobarbital-mediated enzyme induction in the rat. Pharm Res. 23: 521-32 (2006). Reproduced with permission. © 2006 Springer Science and Business Media. IV M. O. Magnusson, M-L. Dahl, J. Cederberg, M. O. Karlsson, and R. Sandström. Pharmacodynamics of enzyme induction attributable to carbamazepine treatment using midazolam, caff eine and digoxin as probes for CYP3A, CYP1A2 and P-glycoprotein. In manuscript. Contents Introduction .......................................................................................11 Background .................................................................................................11 Biotransformation of Xenobiotics ...............................................................12 Cytochrome P450 ..................................................................................... 12 Phase II Metabolism ..................................................................................12 Effl ux Transporters .....................................................................................13 Overlapping Substrate Specifi city............................................................... 13 Mechanisms of Enzyme Induction .............................................................13 Nuclear Receptors and Inducible Proteins .................................................14 Drug-drug Interactions ...............................................................................14 Inducing Drugs ......................................................................................... 14 Th e Consequences of Enzyme Induction .................................................. 14 Interactions Caused by Enzyme Induction .................................................15 Interactions Caused by P-glycoprotein Induction ..................................... 16 Enzyme Activity and Protein Abundance ...................................................16 In Vitro Techniques ....................................................................................16 In Vivo Techniques ....................................................................................16 In Vitro-In Vivo Extrapolation .................................................................... 17 Pharmacodynamics of Enzyme Induction ...................................................17 Half-life of the Induced Enzyme ................................................................18 Pharmacokinetics of the Inducing Agent ................................................... 19 Th e Stimulus Function .............................................................................. 19 Delayed Commencement ................................................................................. 20 Induction Magnitude-Baseline Correlation ...............................................21 Pharmacokinetics of the Aff ected Drug ......................................................21 Non-linear Mixed Eff ect Modelling of Induction ........................................22 Mechanistic Models ...................................................................................22 Non-linear Mixed Eff ect Modelling ...........................................................22 Th e Structure of the Model ........................................................................23 Characteristics of Compounds ....................................................................23 Inducing Agents ........................................................................................ 23 Phenobarbital ................................................................................................... 23 Carbamazepine ................................................................................................. 24 Probe Substances ....................................................................................... 24 Testosterone ...................................................................................................... 24 Resorufi n ..........................................................................................................24 Midazolam ....................................................................................................... 24 Caff eine ............................................................................................................24 Digoxin ............................................................................................................ 24 Aims ...................................................................................................25 Materials and methods .......................................................................26 Experimental Procedures Preclinical Investigation (Paper III) .....................26 Animals ..................................................................................................... 26 Dosage and Sampling ................................................................................ 26 Microsome Preparation and Incubations ....................................................26 Estimation of the Activity of the CYP-enzymes ......................................... 27 Experimental ProceduresClinical Investigations (Papers II and IV) .............27 Carbamazepine-Clomethiazole Interaction Study (Paper II) ...................... 27 Carbamazepine–Drug Cocktail Interaction Study (Paper IV) .................... 27 Chemical Analysis .......................................................................................28 Eight Metabolites of Testosterone (Papers I and III) ...................................28 Phenobarbital and Resorufi n (Paper III) .................................................... 28 Clomethiazole, NLA-715 and Carbamazepine (Paper II) ...........................29 Carbamazepine and the Cocktail of Drugs (Paper IV) ............................... 29 Validation of Chemical Assays ................................................................... 29 Data Evaluation ..........................................................................................30 Modelling Procedures .................................................................................31 Model for Carbamazepine-Clomethiazole Interaction (Paper II) ................31 Model for Phenobarbital Induction (Paper III) .......................................... 32 Model for Carbamazepine-Drug Cocktail Interaction (Paper IV) .............. 32 Digoxin ............................................................................................................ 33 Carbamazepine ................................................................................................. 33 Midazolam ....................................................................................................... 33 Caff eine ............................................................................................................34 Results and discussion ........................................................................35 Quantifi cation of Eight Metabolites of Testosterone (Paper I).....................35 Assessment of Enzyme Activity ...................................................................37 In Vitro .....................................................................................................