Quantitative Method for Simultaneous Analysis of a 5-Probe Cocktail for Cytochrome P450 Enzymes

The metabolic activity of P450 enzymes in vivo can be determined using selective probe drugs. The simultaneous administration of multiple CYP-specific probe drugs is commonly known as the "cocktail approach." Disadvantages of a cocktail are large volumes of samples required for analysis and time-consuming analyses. The aim of this study was to develop and validate a simplified but sensitive method for the simultaneous quantification of 5 probe drugs [caffeine (CYP1A2), metoprolol (CYP2D6), midazolam (CYP3A4), omeprazole (CYP2C19), and S-warfarin (CYP2C9)] in a previously validated cocktail using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method.

The method entailed a single method for sample preparation that enables quick processing of the samples containing all 5 probe drugs in a small volume of blood (≥10 μL) followed by a chiral and nonchiral LC-MS/MS method. The method was validated for selectivity, specificity, resolution of racemic warfarin, linearity, accuracy, imprecision, recovery, process efficiency, ionization efficiency, and carryover effect.

The method showed good selectivity without matrix interferences and differentiated S- and R-warfarin enantiomers with adequate resolution (Rs = 1.55). For all analytes, the mean process efficiency was >95%, and the mean ionization efficiency was >97%. Furthermore, the accuracy was between 94.9% and 108% for all analytes, and the within- and between-run imprecision were <11.7% for the lower limit of quantification and <12.6% for the middle level and upper limit of quantification.

The method presented here enables the simultaneous quantification of the 5 probes in a very small blood volume (≥10 μL). Furthermore, it is less time consuming than previously reported methods because it requires only 1 simple method for sample preparation followed by a nonchiral and chiral LC-MS/MS method that can be performed sequentially.