• Journal of Pharmaceutical Investigation
• /
• v.30 no.3
• /
• pp.191-199
• /
• 2000

Genomics is providing targets faster than we can validate them and combinatorial chemistry is providing new chemical entities faster than we can screen them. Historically, the drug discovery cascade has been established as a sequential process initiated with a potency screening against a selected biological target. In this sequential process, pharmacokinetics was often regarded as a low-throughput activity. Typically, limited pharmacokinetics studies would be conducted prior to acceptance of a compound for safety evaluation and, as a result, compounds often failed to reach a clinical testing due to unfavorable pharmacokinetic characteristics. A new paradigm in drug discovery has emerged in which the entire sample collection is rapidly screened using robotized high-throughput assays at the outset of the program. Higher-throughput pharmacokinetics (HTPK) is being achieved through introduction of new techniques, including automation for sample preparation and new experimental approaches. A number of in vitro and in vivo methods are being developed for the HTPK. In vitro studies, in which many cell lines are used to screen absorption and metabolism, are generally faster than in vivo screening, and, in this sense, in vitro screening is often considered as a real HTPK. Despite the elegance of the in vitro models, however, in vivo screenings are always essential for the final confirmation. Among these in vivo methods, cassette dosing technique, is believed the methods that is applicable in the screening of pharmacokinetics of many compounds at a time. The widespread use of liquid chromatography (LC) interfaced to mass spectrometry (MS) or tandem mass spectrometry (MS/MS) allowed the feasibility of the cassette dosing technique. Another approach to increase the throughput of in vivo screening of pharmacokinetics is to reduce the number of sample analysis. Two common approaches are used for this purpose. First, samples from identical study designs but that contain different drug candidate can be pooled to produce single set of samples, thus, reducing sample to be analyzed. Second, for a single test compound, serial plasma samples can be pooled to produce a single composite sample for analysis. In this review, we validated the issue whether the second method can be applied to practical screening of in vivo pharmacokinetics using data from seven of our previous bioequivalence studies. For a given drug, equally spaced serial plasma samples were pooled to achieve a 'Pooled Concentration' for the drug. An area under the plasma drug concentration-time curve (AUC) was then calculated theoretically using the pooled concentration and the predicted AUC value was statistically compared with the traditionally calculated AUC value. The comparison revealed that the sample pooling method generated reasonably accurate AUC values when compared with those obtained by the traditional approach. It is especially noteworthy that the accuracy was obtained by the analysis of only one sample instead of analyses of a number of samples that necessitates a significant man-power and time. Thus, we propose the sample pooling method as an alternative to in vivo pharmacokinetic approach in the selection potential lead(s) from combinatorial libraries.

• Mass Spectrometry Letters
• /
• v.8 no.4
• /
• pp.98-104
• /
• 2017

Ginseng (Panax ginseng Meyer) is a well-known health functional food used as a traditional herbal drug in Asian countries owing to its diverse pharmacological effects. Herb-drug interactions may cause unexpected side effects of co-administered drugs by the alteration of pharmacokinetics through effects on cytochrome P450 activity. In this study, we investigated the herb-drug interactions between Korean red ginseng extract (KRG) and five CYP-specific probes in mice. The pharmacokinetics of KRG extract induced-drug interactions were studied by cassette dosing of five CYP substrates for CYP1A, 2B, 2C, 2D, and 3A and the LC-MS/MS analysis of the blood concentration of metabolites of each of the five probes. The linearity, precision, and accuracy of the quantification method of the five metabolites were successfully confirmed. The plasma concentrations of five metabolites after co-administration of different doses of the KRG extract (0, 0.5, 1, and 2 g/kg) were quantified by LC-MS/MS and dose-dependent pharmacokinetic parameters were determined. The pharmacokinetic parameters of the five metabolites were not significantly altered by the dose of the KRG extract. In conclusion, the single co-administration of KRG extract up to 2 g/kg in vivo did not cause any significant herb-drug interactions linked to the modulation of CYP activity.