Prediction of herb-drug interactions involving consumption of furanocoumarin-mixtures and cytochrome P450 1A2-mediated caffeine metabolism inhibition in humans

Abstract Herb-drug interaction (HDI) has become important due to the increasing popularity of natural product consumption worldwide. HDI is difficult to predict as botanical drugs usually contain complex phytochemical-mixtures which interact with drug metabolism. Currently, there is no pharmacological tool to predict HDI since almost all in vitro-in vivo-extrapolation (IVIVE) Drug-Drug Interaction (DDI) models deal with one inhibitor-drug and one victim-drug. The objectives were to modify IVIVE models of Mayhew et al. (2000) and Wang et al. (2004) for prediction of in vivo interaction between caffeine and furanocoumarin-containing herbs, and to confirm model prediction by comparing the predictive results with experimental data. The models were modified to predict in vivo herb-caffeine interaction using the same set of inhibition constants but different integrated dose/concentration of furanocoumarin mixtures in the liver. Different hepatic inlet inhibitor concentration ([I]H) surrogates were used for each furanocoumarin. In the Mayhew et al., the [I]H was predicted using the concentration-addition model for chemical-mixtures. In the Wang et al., the [I]H was calculated by adding individual furanocoumarins together. Once [I]H was determined, the models predicted an area-under-curve-ratio (AUCR) of each interaction. The results indicate that both models were able to predict the experimental AUCR of herbal products reasonably well.