The early detection of potential drug-drug interactions is an important issue of drug discovery that has led to the development of high-throughput screening (HTS) methods for potential drug interactions. We developed a HTS method for potential interactions of inhibitory drugs for nine human P450 enzymes using cocktail incubation and tandem mass spectrometry in vitro. This new method involves incubation of two cocktail doses and single cassette analysis. The two cocktail doses in vitro were developed to minimize solvent effects and mutual drug interactions among substrates: cocktail A was composed of phenacetin for CYP1A2, coumarin for CYP2A6, paclitaxel for CYP2C8, S-mephenytoin for CYP2C19, dextromethorphan for CYP2D6, and midazolam for CYP3A4; and cocktail B was composed of three substrates including bupropion for CYP2B6, tolbutamide for CYP2C9, and chlorzoxazone for CYP2E1. In the incubation study of these cocktails, the reaction mixtures were pooled and simultaneously analyzed using liquid chromatography/tandem mass spectrometry employing a fast gradient. The method was validated by comparing the inhibition data obtained from the incubation of each individual probe substrate alone with data from the new method. The IC50 value of each inhibitor in the cocktail agreed well with that of the individual probe drug as well as with values previously reported in the literature. As a HTS method for potential interactions of the inhibition of these nine P450 enzymes, this new method will be useful in the drug discovery process and for the mechanistic understanding of drug interactions.

ABSTRACT:There have been very limited reports on the effects of commercial fruit juices on human CYP3A activity. Therefore, the inhibitory effects of readily available commercial fruit juices on midazolam 1-hydroxylase activity, a marker of CYP3A, were evaluated in pooled human liver microsomes. The fruit juices investigated were black raspberry, black mulberry, plum, and wild grape. White grapefruit, pomegranate, and orange juice were used as positive and negative controls. The black mulberry juice showed the most potent inhibition of CYP3A except for grapefruit juice. The inhibition depended on the amount of a fruit juice added to the incubation mixture. The inhibitory potential of human CYP3A was in the order: grapefruit > black mulberry > wild grape > pomegranate > black raspberry. The IC 50 values of all fruit juices tested were reduced after preincubation with microsomes in the presence of the NADPH-generating system, suggesting that a mechanismbased inhibitory component was present in these fruit juices, as in the case of grapefruit. The results suggest that, like grapefruit juice, commercial fruit juices also have the potential to inhibit CYP3A-catalzyed midazolam 1-hydroxylation. Therefore, in vivo studies investigating the interactions between fruit juices such as black mulberry and wild grape and CYP3A substrates are necessary to determine whether inhibition of CYP3A activity by fruit juices is clinically relevant.Several fruits have been reported to cause food-drug interactions, including grapefruit (Bailey et al., 1998) and pomegranate (Hidaka et al., 2005). As a well known example, consumption of grapefruit juice has been shown to increase the plasma concentration of drugs, such as calcium channel antagonists (Bailey et al., 1993(Bailey et al., , 1998, cyclosporine (Yee et al., 1995), midazolam (Kupferschmidt et al., 1995), HIV protease inhibitors (Kupferschmidt et al., 1998), and HMG-CoA reductase inhibitors (Lilja et al., 1998(Lilja et al., , 1999. A single glass of grapefruit juice has the potential to augment the oral bioavailability and to enhance the beneficial or adverse effects of a broad range of medications.Cytochrome P450 (P450) is a representative enzyme involved in hepatic drug metabolism, which is crucial for the elimination of many therapeutic drugs. Among the members of the P450 family, CYP3A is the most important enzyme and is involved in the majority of the P450-catalyzed metabolism (Guengerich, 1996). Studies have shown that grapefruit juices strongly inhibited drug metabolism mediated by the CYP3A subfamily in the gut wall (Bailey et al., 1998). Conversely, it has been documented that orange juice is incapable of inhibiting the catalytic activity of CYP3A, based on the previous results that the systemic exposure of felodipine, a CYP3A substrate, was not affected by orange juice (Bailey et al., 1991). Taking these results into account, the inhibitory effects of a fruit appeared to depend on the fruit species because of the difference of the components contained in each fruit (Guo...

The effect of 3-O-methyl-D-chiro-inositol (D-pinitol), purified from soybean, on the postprandial blood glucose response in patients with type 2 diabetes mellitus was examined. Fifteen Korean subjects with type 2 diabetes mellitus (seven men, eight women; 60.3 +/- 3.1 years old) ingested cooked white rice containing 50 g of available carbohydrate with or without prior ingestion of soy pinitol. Pinitol was given either as a 1.2 g dose at 0, 60, 120, or 180 minutes prior to rice ingestion, or as a 0.6 g dose at 60 minutes prior to rice ingestion. Capillary blood glucose levels were monitored for 4 hours after rice consumption. The ingestion of 1.2 g of pinitol 60 minutes prior to rice consumption controlled postprandial capillary blood glucose most effectively, significantly diminishing the postprandial increase in plasma glucose levels measured at 90 and 120 minutes after rice consumption (P < .05). The incremental area under the plasma glucose response curve for subjects who consumed both pinitol and rice was significantly lower than that for subjects who consumed only rice (P < .05), but pinitol had no apparent effect on postprandial insulin levels. Therefore, soybean-derived pinitol may be useful in controlling postprandial increases in blood glucose in patients with type 2 diabetes.

The effect of MDR1 G2677T/C3435T haplotypes on fexofenadine disposition are magnified in the presence of itraconazole. Itraconazole pretreatment significantly altered the disposition of fexofenadine and thus its peripheral antihistamine effects.