Assessment of pharmacokinetics, bioavailability and protein binding of anacetrapib in rats by a simple high-performance liquid chromatography-tandem mass spectrometry method

Simultaneous Determination of Schisandrin and Promethazine with Its Metabolite in Rat Plasma by HPLC-MS/MS and Its Application to a Pharmacokinetic Study

This study aimed to develop a selective, simple, and sensitive HPLC-MS/MS method for the simultaneous determination of schisandrin and promethazine (PMZ) with its metabolite in rat plasma, which was further used for a pharmacokinetic herb-drug interaction study. HPLC-MS/MS analyses were performed on an Agilent Technologies 1290 LC and a 6410 triple quadrupole mass spectrometer. The following parameters, the lower limit of quantification (LLOQ), calibration curve, accuracy, precision, stability, matrix effect, and recovery, were validated. The linear range of the developed method for PMZ, its metabolite promethazine sulfoxide (PMZSO), and schisandrin in rat plasma was 0.5–200 ng/mL (R² > 0.995), with an LLOQ of 0.5 ng/mL, which completely met the determination requirements of biosamples. The intra- and interday precision (RSD, %) was below 13.31% (below 16.67% for the LLOQ) in various plasma, whose accuracy (bias, %) was from −8.52% to 11.40%, which were both within an acceptable range. This method was successfully applied to a pharmacokinetic herb-drug interaction study after oral administration of PMZ with or without S. chinensis water extract. The results demonstrated that coadministration with the S. chinensis water extract might affect the pharmacokinetic behaviors of PMZ. In turn, when taken together with PMZ, the pharmacokinetic parameters of schisandrin, the main active component of S. chinensis, were also affected. The method established in the current study was selective, simple, sensitive, and widely available with good linearity, high accuracy and precision, and a stable sample preparation process. Moreover, this analytical method provides a significant approach for the investigation of herb-drug interaction between S. chinensis and PMZ. The potential pharmacokinetic herb-drug interaction of PMZ- and schisandrin-containing preparations should be noted.

A Simple HPLC Method for the Quantitative Determination of Silybin in Rat Plasma: Application to a Comparative Pharmacokinetic Study on Commercial Silymarin Products

Silybin (SBN) is a major active constituent of silymarin, a mixture of flavonoids found in fruits and seeds of milk thistle. The aim of this study was to describe a simple bioanalytical method for quantifying SBN in rat plasma. A simple protein deproteinization procedure with acetonitrile (ACN) was employed for plasma sample preparation. A reversed column and gradient elution of a mobile phase (mixture of phosphate buffer (pH 5.0) and ACN) were used for chromatographic separation. The selectivity, linearity (50–5000 ng/mL), precision, accuracy, recovery, matrix effect, and stability for this method were validated as per the current Food and Drug Administration (FDA) guidelines. Our method for SBN was applied to a comparative pharmacokinetic study on four different commercial silymarin products. This in vivo rat study demonstrated that product #4 significantly enhanced the relative oral bioavailability of SBN, as compared to product #1–3. Therefore, the bioanalytical method proposed herein could serve as a promising alternative for preclinical pharmacokinetic studies on silymarin products and, by extension, clinical use after partial modification and validation.

Differential regulation of intestinal and hepatic CYP3A by 1α,25-dihydroxyvitamin D3 : Effects on in vivo oral absorption and disposition of buspirone in rats

1α,25-Dihydroxyvitamin D₃ (also called 1,25(OH)₂ D₃ or calcitriol) is the biologically active form of vitamin D, which functions as a ligand to the vitamin D receptor (VDR). It was previously reported that intestinal cytochrome P450 3A (CYP3A) expression was altered by 1,25(OH)₂ D₃ -mediated VDR activation. However, to clarify whether the change in CYP3A subfamily expression by VDR activation can affect metabolic function, further evidence is needed to prove the effect of 1,25(OH)₂ D₃ treatment on CYP3A-mediated drug metabolism and pharmacokinetics. Here, we report the effects of 1,25(OH)₂ D₃ on CYP3A activity and in vivo pharmacokinetics of buspirone in Sprague-Dawley rats. CYP3A mRNA expression and CYP3A-mediated testosterone metabolism were enhanced in the intestine but were unaffected in the livers of rats treated with 1,25(OH)₂ D₃ . Notably, the oral pharmacokinetic profile of buspirone (CYP3A substrate drug) and 6'-hydroxybuspirone (major active metabolite of buspirone formed via CYP3A-mediated metabolism) was significantly altered, while its intravenous pharmacokinetic profile was not affected by 1,25(OH)₂ D₃ treatment. To the best of our knowledge, this study provides the first reported data regarding the effects of 1,25(OH)₂ D₃ treatment on the in vivo pharmacokinetics of intravenous and oral buspirone in rats, by the differential modulation of hepatic and intestinal CYP3A activity. Our present results could lead to further studies in clinically significant CYP3A-mediated drug-nutrient interactions with 1,25(OH)₂ D₃ , including 1,25(OH)₂ D₃ -buspirone interaction. Preclinical Research & Development.

Modulation of Rat Hepatic CYP1A and 2C Activity by Honokiol and Magnolol: Differential Effects on Phenacetin and Diclofenac Pharmacokinetics In Vivo

Honokiol (2-(4-hydroxy-3-prop-2-enyl-phenyl)-4-prop-2-enyl-phenol) and magnolol (4-Allyl-2-(5-allyl-2-hydroxy-phenyl)phenol) are the major active polyphenol constituents of Magnolia officinalis (Magnoliaceae) bark, which has been widely used in traditional Chinese medicine (Houpu Tang) for the treatment of various diseases, including anxiety, stress, gastrointestinal disorders, infection, and asthma. The aim of this study was to investigate the direct effects of honokiol and magnolol on hepatic CYP1A and 2C-mediated metabolism in vitro using rat liver microsomes and in vivo using the Sprague-Dawley rat model. Honokiol and magnolol inhibited in vitro CYP1A activity (probe substrate: phenacetin) more potently than CYP2C activity (probe substrate: diclofenac): The mean IC₅₀ values of honokiol for the metabolism of phenacetin and diclofenac were 8.59 μM and 44.7 μM, while those of magnolol were 19.0 μM and 47.3 μM, respectively. Notably, the systemic exposure (AUC and C_max) of phenacetin, but not of diclofenac, was markedly enhanced by the concurrent administration of intravenous honokiol or magnolol. The differential effects of the two phytochemicals on phenacetin and diclofenac in vivo pharmacokinetics could at least be partly attributed to their lower IC₅₀ values for the inhibition of phenacetin metabolism than for diclofenac metabolism. In addition, the systemic exposure, CL, and V_ss of honokiol and magnolol tended to be similar between the rat groups receiving phenacetin and diclofenac. These findings improve our understanding of CYP-mediated drug interactions with M. officinalis and its active constituents.

Novel reverse electrodialysis-driven iontophoretic system for topical and transdermal delivery of poorly permeable therapeutic agents

Topical and transdermal drug delivery has great potential in non-invasive and non-oral administration of poorly bioavailable therapeutic agents. However, due to the barrier function of the stratum corneum, the drugs that can be clinically feasible candidates for topical and transdermal delivery have been limited to small-sized lipophilic molecules. Previously, we fabricated a novel iontophoretic system using reverse electrodialysis (RED) technology (RED system). However, no study has demonstrated its utility in topical and/or transdermal delivery of poorly permeable therapeutic agents. In this study, we report the topical delivery of fluorescein isothiocyanate (FITC)–hyaluronic acid (FITC–HA) and vitamin C and the transdermal delivery of lopinavir using our newly developed RED system in the in vitro hairless mouse skin and in vivo Sprague–Dawley rat models. The RED system significantly enhanced the efficiency of topical HA and vitamin C and transdermal lopinavir delivery. Moreover, the efficiency and safety of transdermal delivery using the RED system were comparable with those of a commercial ketoprofen patch formulation. Thus, the RED system can be a potential topical and transdermal delivery system for various poorly bioavailable pharmaceuticals including HA, vitamin C, and lopinavir.