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Abstract
Self-administration of complementary products concurrently with conventional medication is increasingly common. The potential for cytochrome P450 (CYP) inhibition requires investigation. The N-in-one assay with ten probe substrates for nine CYPs was used with human liver microsomes to investigate ten products. CYP inhibition was measured in a single liquid chromatography-tandem mass spectrometry (LC/MS-MS) analysis. Estimated IC50-values were determined for the extracts that produced significant inhibition (less than 100 μg ml−1).
Inhibition of CYP2C19 by dong quai (IC50 = 13.7–14.3 μg ml−1 for the methanolic extract) and CYP2D6 by goldenseal (IC50 = 6.7 and 6.3 μg ml−1 for the aqueous and methanolic extracts, respectively), are of particular concern as the potential for adverse interactions is high. The inhibition of CYP2C8 by horsetail (IC50 = 93 μg ml−1 for the aqueous extract) requires further investigation, as the potential for concurrent use with products that require CYP2C8 for metabolism is significant. CYP3A4 inhibition varied depending on the probe reaction being monitored.
The earlier reported findings of inhibition by black cohosh, goldenseal and gotu kola were confirmed. The present work has shown that the N-in-one cocktail is a rapid and reliable method that can be used as an initial screen to help prioritize products that require more detailed investigations and it can also be applied to monitor product variability.
Acknowledgements
The skilful technical assistance of Päivi Tyni and Ritva Tauriainen is gratefully acknowledged. Studies described in this article were supported partially by the Academy of Finland (Research Council for Health Sciences), the Finnish Granting Agency for Innovative Research (TEKES), and the Centre for International Mobility (CIMO).
Declaration of interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.