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Polycyclic aromatic hydrocarbons and amiodarone pharmacokinetics Open Access


Other title
enzyme induction
Type of item
Degree grantor
University of Alberta
Author or creator
Elsherbiny, Marwa
Supervisor and department
Examining committee member and department
Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta.

Date accepted
Graduation date
Doctor of Philosophy
Degree level
In the treatment of arrhythmias, amiodarone is a primary therapeutic agent. Cytochromes P450 (CYP) 1A1 and 1A2 facilitate biotransformation of amiodarone to the biologically active desethylamiodarone. Side effects have been reported during therapy and some are correlated with increased desethylamiodarone levels. Exposure to polycyclic aromatic hydrocarbons (PAH) like β-naphthoflavone induces CYP1A1 and CYP1A2 and therefore can increase desethylamiodarone levels. Desethylamiodarone, however, was reported to inactivate human CYP1A1 and therefore can conceivably inhibit its CYP1A1-mediated formation. Our primary objective was to investigate the effect of β-naphthoflavone on amiodarone disposition. Since rats were used, CYP isoenzymes involved in desethylamiodarone formation in human were compared to their rat counterparts. The effect of ketoconazole on desethylamiodarone formation, the inactivating potential of desethylamiodarone on CYP1A1 and the mechanism of β-naphthoflavone-amiodarone interaction were assessed. Human CYP1A1 and rat CYP2D1 had the highest intrinsic clearance (Clint) for desethylamiodarone. Human and rat CYP1A2 had the lowest Clint. Ketoconazole (18.8 μM) inhibited all isoforms except for rat CYP1A2; it potently inhibited human CYP1A1 and CYP3A4 and rat CYP2D2 and CYP1A1. After a single amiodarone dose was administered to control and β-naphthoflavone pretreated rats, the plasma area under concentration-time curve (AUC) of desethylamiodarone increased. With multiple doses, amiodarone AUC(0-24h) decreased in β-naphthoflavone plasma (30%), lung (35%), liver (48%), kidney (52%), heart (34%), and intestine (43%). Desethylamiodarone AUC(0-24h) increased in β-naphthoflavone plasma (36%), lung (56%), liver (101%), kidney (65%), and heart (73%). Desethylamiodarone caused no inactivation of CYP1A1 when preincubations were diluted and nicotinamide adenine dinucleotide phosphate (NADPH) was added in the probe incubation samples. Evidence for reversible mixed-competitive inhibition was apparent. Addition and/or replenishment of NADPH were important factors in maintaining control activity. Β-naphthoflavone increased desethylamiodarone formation only in lung and kidney microsomes. Desethylamiodarone formation in liver, intestine and heart microsomes was not altered. Body-weight-normalized liver mass was significantly increased (27%) by β-naphthoflavone. In conclusion, human CYP1A1 was more efficient in forming desethylamiodarone than rat isoenzyme. Exposure to PAH increased desethylamiodarone levels in vivo. Increased desethylamiodarone levels were partly caused by CYP1A1 induction, and by increased liver mass. Desethylamiodarone did not inactivate CYP1A1 activity.
License granted by Marwa Elsherbiny ( on 2010-09-28T21:52:38Z (GMT): Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of the above terms. The author reserves all other publication and other rights in association with the copyright in the thesis, and except as herein provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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