Effects of fish CYP inducers on difloxacin <Emphasis Type="Italic">N</Emphasis>-demethylation in kidney cell of Chinese idle (<Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis>)

A drug–drug interaction occurs when the effect of one drug is altered by the presence of another drug which is generally associated with the induction of cytochrome P450s (CYPs) activity. Thus, unexpected treatment failures often happen resulting from inappropriate coadministration in fisheries. However, little information is available about CYP induction in fish. The reaction of difloxacin (DIF) biotransformation to sarafloxacin (SAR) belongs to N-demethylation catalyzed mainly by CYP(s). In order to supply useful information on CYP induction, the present study assessed the effects of fish-specific CYP inducers on DIF N-demethylation and enzyme kinetics in kidney cell of Chinese idle (CIK; grass carp (Ctenopharyngodon idellus)) by RP-HPLC. Results demonstrated that the amounts of SAR formation and enzymatic parameters Clint and Vmax were significantly increased due to β-naphthoflavone (BNF) pretreatment. Therefore, we suggest that CYP1A may be involved in DIF N-demethylation in CIK. This study provides instructive information to ensure treatment success via avoiding CYP induction in fisheries.