A simple and sensitive HPLC-MS/MS assay for the quantitation of montelukast in cell-based systems in vitro pulmonary drug permeability study

Montelukast is a potent and selective antagonist of the cysteinyl leukotriene receptor 1 subtype (CysLT1) and widely used in the form of oral tablets and granules for asthma prophylaxis and treatment. Recently, due to the pulmonary inhaled administration can limit montelukast distribution in the systemic circulation, avoid the first-pass metabolism and have better therapeutic effects in respiratory disease treatment, explore alternative routes of administration, like delivery of montelukast via an inhaled, is a new research trend for montelukast. The aim of the current study was to develop and validate a simple, accurate, highly sensitive and selective liquid chromatography-tandem mass spectrometry method (LC-MS/MS) for determination of montelukast in an in vitro cell-based pulmonary pharmacokinetics system model, which can be used to be a better understanding the fate of inhaled montelukast in the lungs. In this study, montelukast was extracted by protein precipitation with acetonitrile containing labeled montelukast. The chromatography was performed on an Agilent Eclipse plus C8 column (4.6 mm × 100 mm, 3.5 μm, Darmstadt, Germany) operating at 35 ◦C. The mobile phase consisted of acetonitrile: 20 mM ammonium formate buffer (80: 20, v/v), was delivered at a flow rate of 0.5 mL/min. montelukast and the internal standard were both eluted at 4.2 min. A linear (1/x²) relationship was used to perform the calibration over an analytical range from 0.5 to 600 ng/mL. The intra- and inter-batch precision expressed as CV for four QC samples including LLOQ range from 1.14 % to 6.25 %. The intra- and inter-batch accuracy for four concentrations of montelukast were in the range of 95.19%-104.1%. All the values for accuracy and precision were within the acceptance range. The method met all the bioanalytical method validation requirements by ICH and was suitable for the assay of montelukast which in the in vitro cell-based pulmonary pharmacokinetics system model.

Ginsenoside Rg1 protects human renal tubular epithelial cells from lipopolysaccharide-induced apoptosis and inflammation damage

Ginsenoside Rg1, one of the most notable active components of Panax ginseng, has been widely reported to exert anti-inflammatory actions. This study aimed to reveal whether ginsenoside Rg1 also exhibits beneficial roles against lipopolysaccharide (LPS)-induced apoptosis and inflammation in human renal tubular epithelial cells, and to evaluate the potential role of the component on tubulointerstitial nephritis treatment. HK-2 cells were treated with various doses of ginsenoside Rg1 (0, 50, 100, 150, and 200 μM) in the absence or presence of 5 μg/mL LPS. Thereafter, CCK-8 assay, flow cytometry, western blot, migration assay, reactive oxygen species (ROS) assay, and ELISA were carried out to respectively assess cell viability, apoptosis, migration, ROS activity, and the release of inflammatory cytokines. As a result, ginsenoside Rg1 protected HK-2 cells from LPS-induced injury, as cell viability was increased, cell apoptosis was decreased, and the release of MCP-1, IL-1β, IL-6, and TNF-α was reduced. Ginsenoside Rg1 functioned to HK-2 cells in a dose-dependent manner, and the 150 μM dose exhibited the most protective functions. Ginsenoside Rg1 had no significant impact on cell migration and ROS activity, while it alleviated LPS-induced ROS release and migration impairment. Furthermore, the down-regulations of p-PI3K, p-AKT, and up-regulations of PTEN, p-IκBα, p-p65, Bcl-3 induced by LPS were recovered to some extent after ginsenoside Rg1 treatment. In conclusion, ginsenoside Rg1 protects HK-2 cells against LPS-induced inflammation and apoptosis via activation of the PI3K/AKT pathway and suppression of NF-κB pathway.

Effects of food and grapefruit juice on single-dose pharmacokinetics of blonanserin in healthy Chinese subjects

PURPOSE

The purpose of this study was to investigate the potential effects of a meal and grapefruit juice on the pharmacokinetics of blonanserin and its metabolite N-desethyl blonanserin in healthy Chinese volunteers.

METHODS

This was a single-centre, open-label, fixed-sequence study, where 12 healthy Chinese volunteers received a single dose of 8 mg blonanserin after an overnight fast in period 1 (reference), a high-fat meal during period 2 and with co-administration of 250 mL of grapefruit juice in period 3. The washout period was 7 days. Series of plasma samples were collected after each dose to determine concentrations of blonanserin and its metabolite N-desethyl blonanserin using liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were estimated by non-compartmental analysis and compared between periods by standard average bioequivalence ANOVA. Adverse events were monitored throughout the study.

RESULTS

All subjects completed the study. High-fat meals significantly increased blonanserin exposure (AUC_t) 2.58-fold (90% CI 2.21, 3.02), relative to the reference period. Co-administration of blonanserin with grapefruit juice remarkably prolonged elimination half-life of blonanserin (from 9.7 to 21.4 h) and significantly increased exposures to blonanserin and N-desethyl blonanserin by 5.82-fold (90% CI 4.57, 7.42) and 1.81-fold (90% CI 1.65, 1.98), respectively.

CONCLUSIONS

These results suggested that blonanserin was largely metabolised in the intestinal tract before becoming systemically available, and both food and grapefruit juice enhanced exposure to blonanserin and N-desethyl blonanserin. Grapefruit juice increased bioavailability and may have reduced systemic clearance of blonanserin. Further intestinal CYP3A4 and hepatic CYP3A4 might be postulated to explain the delayed elimination of blonanserin. Dose adjustment of blonanserin is needed on the basis of co-intake of known strong CYP3A4 inhibitor. Patients taking high-dose blonanserin also need to be cautious about the ingestion of grapefruit juice.

A Simple HPLC-MS/MS Method for Determination of Tryptophan, Kynurenine and Kynurenic Acid in Human Serum and its Potential for Monitoring Antidepressant Therapy

The kynurenine pathway, in which tryptophan is metabolized to kynurenine and kynurenic acid, has been linked to depression. A rapid and highly reproducible liquid-chromatography-tandem mass spectrometry (LC-MS/MS) method were established for determining tryptophan, kynurenine and kynurenic acid in human serum. Biological samples were precipitated with methanol before separation on an Agilent Eclipse XDB-C18. The stable-isotope-labeled internal standards (kynurenine-¹³C₄¹⁵N and kynurenic acid-d₅) were used for quantification. Detection was performed using multiple reaction monitoring in electrospray ionization mode at m/z 205.1→188.1 for tryptophan, m/z 209.1→146.1 for kynurenine, m/z 190.1→144.1 for kynurenic acid. Good linearity of analyte to internal standard peak area ratios was seen in the concentration range 1,000-50,000 ng/mL for tryptophan, 100-5,000 ng/mL for kynurenine and 1-60 ng/mL for kynurenic acid. Pooled drug-free human serum was purified using activated charcoal and the method was shown to be linear, with validation parameters within acceptable limits. The newly developed method was successfully used to determine concentrations of tryptophan, kynurenine and kynurenic acid in serum from 26 healthy volunteers and 54 patients with depression. Concentrations of tryptophan and kynurenine were lower in serum from depressed individuals than from healthy individuals.

Simultaneous determination of pirfenidone and its metabolite in human plasma by liquid chromatography-tandem mass spectrometry: application to a pharmacokinetic study

A simple and rapid analytical method for the simultaneous determination of pirfenidone and its metabolite, 5-carboxy-pirfenidone, in human plasma using liquid chromatography-tandem mass spectrometry has been developed and validated. Aliquots of plasma (0.1 mL) containing pirfenidone and 5-carboxy-pirfenidone, as well as deuterium-labeled internal standards (ISs), were deproteinized using acetonitrile. An Agilent Zorbax Plus C18 column was used for the chromatography, with isocratic elution. The mobile phase was a mixture of acetonitrile and aqueous ammonium formate solution (5 mM) containing 0.1% formic acid (60 : 40, v/v). Using multiple reaction monitoring in positive ionization mode, transitions m/z 186.1 → 65.1, m/z 216.0 → 77.0, m/z 191.1 → 65.1 and m/z 221.0 → 81.0 were chosen to quantify pirfenidone, 5-carboxy-pirfenidone and the two ISs, respectively. The time of analysis was <3 min. The calibration curve was linear over the concentration ranges 0.005-25 μg/mL for pirfenidone, and 0.005-15 μg/mL for 5-carboxy-pirfenidone. The lower limit of quantification for both analytes was 0.005 μg/mL. The intra- and interday precision and relative errors in quality control samples were between -11.7 and 1.3% for pirfenidone and between -5.6 and 2.5% for 5-carboxy-pirfenidone, with mean recoveries ≥90%. The method that has been developed is easy to carry out, sensitive and rapid, and has been successfully used to investigate the pharmacokinetics of pirfenidone in healthy human volunteers.

Determination of allopurinol and oxypurinol in human plasma and urine by liquid chromatography-tandem mass spectrometry

Allopurinol is used widely for the treatment of gout, but its pharmacokinetics is complex and some patients show hypersensitivity, necessitating careful monitoring and improved detection methods. In this study, a sensitive and reliable liquid chromatography-tandem mass spectrometry method was developed to determine the concentrations of allopurinol and its active metabolite oxypurinol in human plasma and urine using 2,6-dichloropurine as the internal standard (IS). Analytes and the IS were extracted from 0.5ml aliquots of plasma or urine using ethyl acetate and separated on an Agilent Eclipse Plus C18 column using methanol and ammonium formate-formic acid buffer containing 5mM ammonium formate and 0.1% formic acid (95:5, v/v) as the mobile phase (A) for allopurinol or methanol plus 5mM ammonium formate aqueous solution (95:5, v/v) as the mobile phase (B) for oxypurinol. Allopurinol was detected in positive ion mode and the analysis time was about 7min. The calibration curve was linear from 0.05 to 5μg/mL allopurinol in plasma and 0.5-30μg/mL in urine. The lower limit of quantification (LLOQ) was 0.05μg/mL in plasma and 0.5μg/mL in urine. The intra- and inter-day precision and relative errors of quality control (QC) samples were ≤11.1% for plasma and ≤ 8.7% for urine. Oxypurinol was detected in negative mode with an analysis time of about 4min. The calibration curve was linear from 0.05 to 5μg/mL in plasma (LLOQ, 0.05μg/mL) and from 1 to 50μg/mL in urine (LLOQ, 1μg/mL). The intra- and inter-day precision and relative errors were ≤7.0% for plasma and ≤9.6% for urine. This method was then successfully applied to investigate the pharmacokinetics of allopurinol and oxypurinol in humans.

Population pharmacokinetics of blonanserin in Chinese healthy volunteers and the effect of the food intake

OBJECTIVE

The aim of the study was to better understand blonanserin population pharmacokinetic (PK) characteristics in Chinese healthy subjects.

METHODS

Data from two studies with 50 subjects were analyzed to investigate the population PK characteristics of blonanserin at single dose (4, 8, and 12 mg) under fasting, multidose (4 mg bid or 8 mg qd for 7 days) and under food intake condition (single dose, 8 mg). Blonanserin plasma concentrations were detected using the high performance liquid chromatography tandem mass spectrometry (LC/MS/MS). A nonlinear mixed-effects model was developed to describe the blonanserin concentration-time profiles.

RESULTS

A two compartment model with first-order absorption was built to describe the time-course of blonanserin. The population-predicted system apparent clearance (CL/F), volume of apparent distribution in center (V(1)/F), and the first-order absorption rate constant (Ka) of blonanserin under fasting was 1230 L/h, 9500 L, and 3.02 h(-1), respectively. Food intake decreased Ka of blonanserin to 0.78 h(-1). The relative bioavailability between fasting and food intake estimated by the final model was 55%. No clinically significant safety issues were identified.

CONCLUSION

This is the first study assessing the PK profile of blonanserin with population PKs method. The results can be used for simulation in further clinical trial and optimize individual dosage regimens using a Bayesian methodology in patients.