Concurrent use with inhibitors or inducers of the cytochrome (CYP) P450 isoenzymes CYP1A2, CYP2D6, and/or CYP3A4 can result in altered concentrations of mirtazapine, as these are the main enzymes responsible for its metabolism.[4][2] As examples, fluoxetine and paroxetine, inhibitors of these enzymes, are known to modestly increase mirtazapine levels, while carbamazepine, an inducer, considerably decreases them.[4] Liver impairment and moderate chronic kidney disease have been reported to decrease the oral clearance of mirtazapine by about 30%; severe kidney disease decreases it by 50%.[4]