Development and validation of an LC–MS/MS method for quantification of NC-8 in rat plasma and its application to pharmacokinetic studies

ent-16-Oxobeyeran-19-N-methylureido (NC-8) is a recently synthesized derivative of iso-steviol that showed anti-hepatitis B virus (HBV) activity by disturbing replication and gene expression of the HBV and by inhibiting the host toll-like receptor 2/nuclear factor-κB signaling pathway. To study its pharmacokinetics as a part of the drug development process, a highly sensitive, rapid, and reliable liquid chromatography tandem mass spectrometry (LC–MS/MS) method was developed and validated for determining NC-8 in rat plasma. After protein precipitation extraction, the chromatographic separation of the analyte and internal standard (IS; diclofenac sodium) was performed on a reverse-phase Luna C₁₈ column coupled with a Quattro Ultima triple quadruple mass spectrometer in the multiple-reaction monitoring mode using the transitions, m/z 347.31 → 75.09 for NC-8 and m/z 295.89 → 214.06 for the IS. The lower limit of quantitation was 0.5 ng/mL. The linear scope of the standard curve was between 0.5 and 500 ng/mL. Both the precision (coefficient of variation; %) and accuracy (relative error; %) were within acceptable criteria of <15%. Recoveries ranged from 104% to 113.4%, and the matrix effects (absolute) were nonsignificant (CV ≤ 6%). The validated method was successfully applied to investigate the pharmacokinetics of NC-8 in male Sprague–Dawley rats. The present methodology provides an analytical means to better understand the preliminary pharmacokinetics of NC-8 for investigations on further drug development.     

LC−MS/MS assay for the determination of a novel anti‐fibrotic candidate mefunidone in monkey plasma and its application to a pharmacokinetics study

Mefunidone (MFD) is a promising anti‐fibrotic candidate molecule with greater anti‐fibrotic activity than pirfenidone (PFD). However, there has been no report on the methodology used for the quantification of MFD or on any investigation of its pharmacokinetics. In this study, an efficient and reliable liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed to assay MFD in monkey plasma. This assay method was validated and applied to a pharmacokinetics study in monkeys. The lower limit of quantification of this assay was 0.1 μg·mL^?1, and the linear calibration curve was acquired with R² > 0.99 between 0.1 and 60 μg·mL^?1. The intra‐day and inter‐day precision were evaluated with coefficient of variations of 1.5%–5.8%, whereas the mean accuracy ranged from 91.7% to 106.9%. A negligible matrix effect and good recovery were obtained using this assay, with average extraction recoveries of MFD and the internal standard (IS) in the range of 85.5%–124.8% and 84.1%–94.0%, respectively. The precision of the absolute matrix effect of MFD and the IS was 1.2–3.0% and 1.2–7.3%, respectively. The samples were stable under all experimental conditions. Linear pharmacokinetics were observed for MFD in monkeys, where the exposures of MFD increased proportionally with increasing MFD doses at the range of 10–90 mg·kg^?1. Moderate elimination of MFD from the body was observed, with t_1/2 of 5–7 h, and the elimination rate of MFD was stable during multiple dosing. In conclusion, this method provides an reliable analytical approach for quantification of MFD in plasma and was successfully applied to a pharmacokinetics study in monkeys.     

Development and validation of a DESI‐HRMS/MS method for the fast profiling of esomeprazole and its metabolites in rat plasma: a pharmacokinetic study

The advances in pharmaceutical development and drug discovery impose the availability of reliable high‐throughput screening methods for the rapid evaluation of drug metabolism and pharmacokinetic (PK) in biological samples. Here, a desorption electrospray mass spectrometry (DESI‐MS) method has been developed and validated for the PK profiling of esomeprazole and its metabolites (5‐hydroxyomeprazole and omeprazole sulfone) in rat plasma. Rats were treated with an esomeprazole solution (2.5 mg/mL) for endovenous administration and the analyte levels were profiled over 2 h after liquid‐liquid extraction from plasma. MS and tandem mass spectrometry (MS/MS) experiments were performed by using a DESI‐LTQ‐Orbitrap XL instrument and an on‐spot fixed time analysis on PMMA surfaces. Validation was performed for the esomeprazole. The DESI‐MS/MS method exhibited for the esomepazole excellent sensitivity (limit of detection (LOD)=60 ng/mL), linearity (0.2‐20 µg/mL concentration range; y=23848(±361)X, n=15; r²=0.987) and precision (RSD<9%) by using an internal standard method. The PK results were discussed in terms of Area Under the Curve, C_max and T_max. Data reliability was demonstrated by comparison with a liquid chromatography‐tandem mass spectrometry method (p>0.05). The data achieved demonstrated that the DESI‐MS method is suitable for sensitive and fast profiling of a drug and its metabolites at the therapeutic concentration levels. Copyright © 2015 John Wiley & Sons, Ltd.     

Performance evaluation of an aqueous—organic phase separator for post-column reactions in high-performance liquid chromatography, and its application to the enhanced detection of some basic drugs of abuse

A phase separator is described that is suitable for post-column HPLC applications. It operates with commonly used HPLC eluents and immiscible organic solvents as long as the two phases remain immiscible. It is compatible with gradient elution systems. Separation efficiency is routinely better than 0.8, which ensures that analyte peak heights are about 95% of the maximum height under these conditions. An application for the detection of pethidine, cocaine, methadone, piritramide and dipipanone at 0.8–1.8 ng on-column loadings is described.     

Pharmacokinetics of gallic acid and protocatechuic acid in humans after dosing with Relinqing (RLQ) and the potential for RLQ-perpetrated drug–drug interactions on organic anion transporter (OAT) 1/3

ContextRelinqing granules (RLQ) are being used alone or in combination with antibacterial drugs to treat urological disorders.ObjectiveThis study investigates the pharmacokinetics of RLQ in humans and the potential for RLQ-perpetrated interactions on transporters.Materials and methodsTwelve healthy subjects (six women and six men) participated to compare single- and multiple-dose pharmacokinetics of RLQ. In the single-dose study, all 12 subjects received 8 g of RLQ orally. After a 7-d washout period, the subjects received 8 g of RLQ for seven consecutive days (t.i.d.) and then a single dose. Gallic acid (GA) and protocatechuic acid (PCA) in plasma and urine samples were analysed using LC-MS/MS. The transfected cells were used to study the inhibitory effect of GA (50–5000 μg/L) and PCA (10–1000 μg/L) on transporters OAT1, OAT3, OCT2, OATP1B1, P-gp and BCRP.ResultsGA and PCA were absorbed into the blood within 1 h after administration and rapidly eliminated with a half-life of less than 2 h. The mean peak concentrations of GA (102 and 176 μg/L) and PCA (4.54 and 7.58 μg/L) were lower in males than females, respectively. The 24 h urine recovery rates of GA and PCA were about 10% and 5%, respectively. The steady-state was reached in 7 d without accumulation. GA was a potent inhibitor of OAT1 (IC₅₀ = 3.73 μM) and OAT3 (IC₅₀ = 29.41 μM), but not OCT2, OATP1B1, P-gp or BCRP.Discussion and conclusionsGA and PCA are recommended as PK-markers in RLQ-related pharmacokinetic and drug interaction studies. We should pay more attention to the potential for RLQ-perpetrated interactions on transporters.     

Development and validation of an LC‐MS/MS method for simultaneous determination of piperaquine and 97‐63, the active metabolite of CDRI 97‐78, in rat plasma and its application in interaction study

Piperaquine‐dihydroartemisinin combination is the latest addition to the repertoire of ACTs recommended by the World Health Organization (WHO) for treatment of falciparum malaria. Due to the increasing resistance to artemisinin derivatives, CSIR‐CDRI has developed a prospective short acting, trioxane antimalarial derivative, CDRI 97‐78. In the present study, a liquid chromatography‐electrospray ionization‐tandem mass spectrometry (LC–ESI‐MS/MS) method for the simultaneous quantification of piperaquine (PPQ) and 97‐63, the active metabolite of CDRI 97‐78 found in vivo, was developed and validated in 100 μL rat plasma using halofantrine as internal standard. PPQ and 97‐63 were separated using acetonitrile:methanol (50:50, v/v) and ammonium formate buffer (10 mM, pH 4.5) in the ratio of 95:5(v/v) as mobile phase under isocratic conditions at a flow rate of 0.65 mL/min on Waters Atlantis C₁₈ (4.6 × 50 mm, 5.0 µm) column. The extraction recoveries of PPQ and 97‐63 ranged from 90.58 to 105.48%, while for the internal standard, it was 94.27%. The method was accurate and precise in the linearity range 3.9–250 ng/mL for both the analytes, with a correlation coefficient (r) of ≥ 0.998. The intra‐ and inter‐day assay precision ranged from 2.91 to 8.45% and; intra‐ and inter‐day assay accuracy was between 92.50 and 110.20% for both the analytes. The method was successfully applied to study the effect of oral co‐administration of PPQ on the pharmacokinetics of CDRI 97‐78 in Sprague‐dawley rats and vice versa. The co‐administration of CDRI 97‐78 caused significant decrease in AUC_0–∞ of PPQ from 31.52 ± 2.68 to 14.84 ± 4.33 h*µg/mL. However, co‐administration of PPQ did not have any significant effect on the pharmacokinetics of CDRI 97‐78. Copyright © 2015 John Wiley & Sons, Ltd.