An improved LC–MS/MS method for simultaneous evaluation of CYP2C9, CYP2C19, CYP2D6 and CYP3A4 activity

Abstract

Aim: To develop an LC–MS/MS assay to quantitate well-tolerated substrates; midazolam (CYP3A), omeprazole (CYP2C19), dextromethorphan (CYP2D6), losartan (CYP2C9) and their respective metabolites’ concentrations in plasma samples. Patients & methods: A solid-phase extraction method was optimized to extract analytes of interest simultaneously from human plasma samples. The assay analyzed plasma samples collected from patients who received equal or lower than therapeutic doses of CYP substrates. Results: This assay was validated based on the European Medicines Agency guideline for bioanalytical method validation and was sensitive, linear, accurate and precise with acceptable recovery and matrix effects. Conclusion: Small sample volume and dose of cytochrome P450 substrates, short-run time, using stable isotope internal standards and being cost effective are the major advantages of the assay.