Description_x000D_ General description_x000D_ CYP2C19 metabolite of mephenytoin._x000D_ Application_x000D_ 4-Hydroxymephenytoin has been used for developing ultra performance LC (UPLC)- tandem mass spectrometry (MS/MS) assays for evaluating cytochrome P450 (CYP) probe drugs and their relevant metabolites in human urine or plasma samples. 4-hydroxymephenytoin has also been used for developing sub-2-micron particle LC/MS/MS-based methods for analyzing CYP450 probe substrate metabolites._x000D_ Packaging_x000D_ 5, 10 mg in glass bottle_x000D_ Biochem/physiol Actions_x000D_ 4-Hydroxymephenytoin catabolism displays genetic polymorphism and is a direct indicator of Cytochrome P450 2C19 (CYP2C19) activity. Detection and quantification of 4-hydroxymephenytoin in biological samples by HPLC method is well optimized._x000D_ Packaging_x000D_ Bottomless glass bottle. Contents are inside inserted fused cone.