Likun Ding

Simultaneous determination of amoxicillin and ambroxol in human plasma by LC-MS/MS: validation and application to pharmacokinetic study.

A rapid, simple and sensitive LC-MS/MS method was developed for simultaneous determination of amoxicillin and ambroxol in human plasma using clenbuterol as internal standard (IS). The plasma samples were subjected to a simple protein precipitation with methanol. Separation was achieved on a Lichrospher C(18) column (150 mm x 4.6mm ID, dp 5 microm) using methanol (containing 0.2% of formic acid) and water (containing 0.2% of formic acid) as a mobile phase by gradient elution at a flow rate of 1.0 mL/min. Detection was performed using electrospray ionization in positive ion multiple reaction monitoring (MRM) mode by monitoring the ion transitions from m/z 365.9-->348.9 (amoxicillin), m/z 378.9-->263.6 (ambroxol) and m/z 277.0-->203.0 (IS). Calibration curves were linear in the concentration range of 5-20,000 ng/mL for amoxicillin, and 1-200 ng/mL for ambroxol, with the intra- and inter-run precisions of <9% and the accuracies of 100+/-7%. The method has been validated and applied to pharmacokinetic studies of compound amoxicillin and ambroxol hydrochloride tablets in healthy Chinese volunteers.

Pharmacogenetic Variation and Metformin Response

Diabetes is a major health problem worldwide, and metformin, a traditional oral anti-hyperglycemic drug, is now believed to be the most widely prescribed antidiabetic drug. Metformin acts primarily by inhibiting hepatic glucose production and improving insulin sensitivity. Metformin is absorbed predominately by the small intestine and excreted in an unaltered form in the urine. The pharmacokinetics of metformin is primarily determined by membrane transporters, including the plasma membrane monoamine transporter (PMAT), the organic cation transporters (OCTs), the multidrug and toxin extrusion (MATE) transporters, and the critical protein kinase AMPactivated protein kinase (AMPK). PMAT may play a role in the uptake of metformin from the gastrointestinal tract, while OCTs mediate the intestinal absorption, hepatic uptake, and renal excretion of metformin. MATEs are believed to contribute to the hepatic and renal excretion of the drug. The pharmacologic effects of metformin are primarily exerted in the liver, at least partly via the activation of AMPK and the subsequent inhibition of gluconeogenesis. A considerable amount of pharmacogenetic research has demonstrated that genetic variation is one of the major factors affecting metformin response. Moreover, it has become increasingly clear that membrane transporters are important determinants of the pharmacokinetics of metformin. In this review, we will discuss the genetic variants of major transporters that purportedly determine the pharmacokinetics of metformin in terms of drug bioavailability, distribution, and excretion, such as PMAT, OCTs, and MATEs. Understanding how genetic variation affects metformin response will help promote more effective use of the drug for the treatment of type 2 diabetes (T2D).

Protective autophagy promotes the resistance of HER2-positive breast cancer cells to lapatinib

Lapatinib, a tyrosine kinase inhibitor of HER2/EGFR, can inhibit the proliferation of HER2-positive breast cancer cells. Additionally, the combination of lapatinib and chemotherapy can markedly prolong patient survival time. However, the clinical therapeutic effect of lapatinib is severely limited by drug resistance. We previously found that brief treatment with lapatinib induced both apoptosis and autophagy in HER2-positive breast cancer cells. Additionally, the apoptosis induced by lapatinib was dependent on autophagy. In our current study, however, we used extended treatment of HER2-positive breast cancer cells with lapatinib to confirm the presence of protective autophagy in the previously established lapatinib-resistant cells. Specifically, we found that inhibition of autophagy could reduce the proliferation, DNA synthesis, and colony-forming capacity of resistant cells. Thus, autophagy is a potential novel therapeutic target for reversing lapatinib resistance of HER2-positive breast cancer cells. Our data provide clear, novel evidence of both anti-apoptotic and pro-apoptotic functions of autophagy in breast cancer during lapatinib treatment.

The effect of staggered administration of zinc sulfate on the pharmacokinetics of oral cephalexin

AIMS To investigate the effect of zinc sulfate on pharmacokinetics of cephalexin when administered concurrently or at strategically spaced dosing times designed to avoid the potential interaction in healthy volunteers. METHODS In this study, all subjects (n= 12) were randomized to receive the following four treatments, separated by a wash-out period of 7 days: cephalexin 500mg alone, concomitantly with zinc 250mg, 3h after zinc 250mg or 3h before zinc 250mg. RESULTS All subjects completed the study safely. Zinc supplements administered concurrently with cephalexin significantly decreased the peak serum concentration (C(max) ), area under the plasma concentration-time curve from zero to infinity (AUC(0-∞) ) and the time for which the plasma concentration of the drug remained above the minimal inhibitory concentration of the pathogenic organism (T > MIC) of cephalexin [mean percentage decrease (95% confidence intervals) of 31.05% (22.09-40.01%), 27.40% (18.33-36.47%) and 22.33% (12.51-32.16%), respectively; P < 0.05] compared with administration of cephalexin alone. Also, administration of zinc 3h before cephalexin decreased the C(max) , AUC(0-∞) and T > MIC of the drug compared with administration of cephalexin alone [mean percentage decrease (95% confidence intervals) of 11.48% (3.40-19.55%), 18.12% (9.63-26.60%) and 23.75% (14.30-33.20%), respectively; P < 0.05]. In contrast, the pharmacokinetics of cephalexin was not notably altered by administration of zinc 3h after cephalexin dosing (P > 0.05). CONCLUSIONS The significant interaction between zinc and cephalexin might affect the clinical outcome of cephalexin therapy. The dosing recommendation is that zinc sulfate can be safely administered 3h after a cephalexin dose.

A sensitive LC-MS/MS method for determination of levamisole in human plasma: application to pharmacokinetic study.

A sensitive and rapid LC-MS/MS method was developed and validated for the determination of levamisole in human plasma. The assay was based on liquid-liquid extraction of analytes from human plasma with ethyl ether. Chromatographic separation was carried on an Agilent HC-C(8) column (150 mm × 4.6 mm, 5 μm) at 40°C, with a mobile phase consisting of acetonitrile-10 mM ammonium acetate (70:30, v/v), a flow rate of 0.5 mL/min and a total run time of 6 min. Detection and quantification were performed by mass spectrometry in the multiple reaction monitoring mode with positive electrospray ionization m/z at 205.1→178.2 for levamisole, and m/z 296.1→264.1 for mebendazole (internal standard). The assay was linear over a concentration range of 0.1-30 ng/mL with a lower limit of quantification of 0.1 ng/mL. The coefficient of variation of the assay precision was less than 8.5%. The assay was successfully used to analyze human plasma samples in a pharmacokinetic study where levamisole was administered as a liniment.

Iridoid glycosides from the flowers of Gentiana macrophylla Pall. ameliorate collagen-induced arthritis in rats

BACKGROUND The flowers of Gentiana macrophylla have been usually applied to cure the joint inflammation and rheumatoid arthritis in Traditional Chinese Medicine. HYPOTHESIS/PURPOSE This work aimed to investigate the anti-rheumatoid arthritic effect and possible mechanism of iridoid glycosides from G. macrophylla (GMI) using an animal model of collagen-induced rheumatoid arthritis (CIA) in rats. STUDY DESIGN All rats were randomly divided into five groups: normal control, CIA, dexamethasone, 15mg/kg and 30mg/kg GMI. METHODS CIA was induced (day 0) in male Sprague-Dawley rats by intradermal injection of complete Bovine CII at the base of the tail. Dexamethasone was chosen as the positive drug. The administration of different drugs started from day 1 and continued for 28 days. Paw swelling, arthritis score and histopathological changes were examined to assess the severity of arthritis. In addition, the serum levels of tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expressions in joint synovial tissues were detected. RESULTS GMI reduced paw edema, arthritis scores and the index of spleen and thymus from day 7 to 21 after CIA compared with those in the CIA group. Our data also demonstrated that GMI inhibited pro-inflammatory cytokines such as TNF-α, IL-1β and IL-6, regulated the expression of iNOS and COX-2 compared with those in the CIA group. We also obtained four major components from GMI, identified as loganic acid, swertamarin, gentiopicroside and sweroside, and the contents of them were also calculated respectively. CONCLUSION Taken together, our results shed light on the therapeutic efficacy of GMI in rats rheumatoid arthritis model by reducing the levels of IL-1β, IL-6 and TNF-α in serum as well as down-regulating the levels of iNOS and COX-2. Therefore, GMI may be an effective therapy for the treatment of rheumatoid arthritis.

Liquid chromatography/electrospray ionization tandem mass spectrometry for the quantification of mitiglinide in human plasma: validation and its application to pharmacokinetic studies

A sensitive and specific method was developed and validated for the determination of mitiglinide in human plasma using liquid chromatographic separation with electrospray ionization tandem mass spectrometric detection. Acidified plasma samples were extracted with ethyl acetate. The chromatographic separation was performed on an Agilent Zorbax Eclipse Plus C(18) column with a mobile phase of methanol-10 mm ammonium acetate solution at a flow rate of 0.3 mL/min. Analytes were detected with an Agilent 6410 Triple qudrupole mass spectrometer equipped with an electrospray ionization source in positive multiple reaction monitoring mode: m/z 316.2 (precursor ion) to 298.2 (product ion) for mitiglinide and m/z 318.2 (precursor ion) to 120.2 (product ion) for the internal standard. This method was validated over a linear range of 0.5-4000 ng/mL for mitiglinide in human plasma. The lower limit of quantification (LLOQ) was 0.5 ng/mL, while a relative standard deviation (RSD) was less than 3.9%. The intra- and inter-run precision (as RSD, %) obtained from three validation runs were all less than 15%. The validated method was successfully used to analyze human plasma samples for application in pharmacokinetic studies.

Application of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to the pharmacokinetics, tissue distribution and excretion studies of felotaxel (SHR110008) in tumor-bearing mice.

Felotaxel (SHR110008), currently under clinical investigation in phase I trial, is a new effective taxane with greater anticancer activity and less toxicity than docetaxel. Pharmacokinetic studies in animal models are the important components in clinical development of this agent. In this study, a rapid and sensitive analytical method based on high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the determination of felotaxel in tumor-bearing mice plasma, urine, feces and tissues (brain, heart, liver, lung and kidney and tumor). For all matrices, sample preparation involved liquid-liquid extraction with ethyl acetate. Calibration curves (1/x² weighted) offered satisfactory linearity (r² ≥ 0.995) within the test range. The lower limit of quantitation (LLOQ) for all matrices was 10 ng/ml except that for mouse plasma and brain LLOQ was 1 ng/ml. The accuracy and precision ranged from 86.1 to 107.2% and 1.1 to 9.2%, respectively. Recoveries (73.9-96.1%) and matrix effects (76.4-97.2%) were satisfactory in all the biological matrices examined. Stability studies (85.1-101.5%) showed that felotaxel was stable both during the assay procedure and long-term storage. The assay was successfully applied to plasma pharmacokinetics, tissue distribution and excretion study of mice. The pharmacokinetic parameters, such as half-life, mean residence time, maximum concentration were determined. The preclinical data are useful for the design of clinical trials of felotaxel.

Determination of azatadine in human plasma by liquid chromatography/tandem mass spectrometry.

A sensitive method using liquid chromatography with tandem mass spectrometric detection (LC-MS/MS) was developed and validated for the analysis of antihistamine drug azatadine in human plasma. Loratadine was used as internal standard (IS). Analytes were extracted from human plasma by liquid/liquid extraction using ethyl acetate. The organic phase was reduced to dryness under a stream of nitrogen at 30 °C and the residue was reconstituted with the mobile phase. 5 μL of the resulting solution was injected onto the LC-MS/MS system. A 4.6 mm × 150 mm, I.D. 5 μm, Agilent TC-C(18) column was used to perform the chromatographic analysis. The mobile phase consisted of ammonium formate buffer 0.010 M (adjusted to pH 4.3 with 1M formic acid)/acetonitrile (20:80, v/v) The chromatographic run time was 5 min per injection and flow rate was 0.6 mL/min. The retention time was 2.4 and 4.4 min for azatadine and IS, respectively. The tandem mass spectrometric detection mode was achieved with electrospray ionization (ESI) iron source and the multiple reaction monitoring (MRM) (291.3 → 248.2m/z for azatadine, 383.3 → 337.3m/z for IS) was operated in positive ion modes. The low limit of quantitation (LLOQ) was 0.05 ng/mL. The intra-day and inter-day precision of the quality control (QC) samples was 8.93-11.57% relative standard deviation (RSD). The inter-day accuracy of the QC samples was 96.83-105.07% of the nominal values.

Pharmacokinetics of Single-Dose and Multi-Dose of Lovastatin/Niacin ER Tablet in Healthy Volunteers

An extended-release (ER) niacin and lovastatin fixed-dose combination has been developed for the treatment of primary hypercholesterolemia and mixed dyslipidemia. The purpose of the present study was to examine the drug interaction between niacin and lovastatin after multi-dose oral administration of lovastatin/niacin ER combination in healthy Chinese volunteers. A single-center, randomized, open-label, 5-period crossover study was conducted in thirty healthy volunteers aged 18 to 45 years with a washout period of 8 days. Subjects were randomized to receive multiple doses of treatment A (1 500 mg niacin ER tablet), B (1 20 mg lovastatin tablet), C (1 20 mg lovastatin and 500 mg niacin-ER tablet), D (2 10 mg lovastatin and 350 mg niacin-ER tablets) or E (2 10 mg lovastatin and 500 mg niacin-ER tablets) in 1 of 5 sequences (ABCDE, BCDEA, CDEAB, DEABC, EABCD) per period. Lovastatin, niacin and its metabolites (nicotinuric acid and nicotinamide) were determined in plasma by LC/MS method. Pharmacokinetic parameters were calculated, and least square mean ratios and 90% confidence intervals for 𝐶max and AUC(0–24) were determined for lovastatin/niacin ER versus niacin ER or lovastatin. It revealed that the formulation had no potential drug interaction in healthy Chinese volunteers when the dosage was increased from 500 mg to 1000 mg.