Omeprazole In Plasma Research Articles

UHPLC method for simultaneous assessment of pharmacokinetic parameters of co-administered voriconazole and omeprazole using rat plasma

Voriconazole (VRC) is a first-line therapeutic agent for the treatment of invasive fungal infections, whereas omeprazole (OMZ) is a commonly used acid suppressant; however, the two drugs are often used in combination in clinical practice. The aim of this research was to investigate how the co-administration of OMZ and VRC affects the pharmacokinetic characteristics of VRC in rats. A new ultra high-performance liquid chromatography (UHPLC) analytical method was developed and validated for simultaneous analysis of co-administered drugs using VRC and OMZ. A Shim-pack GIST-HP C18 column with 0.1 M triethylamine:acetonitrile (70:30, v/v) as the mobile phase (flow rate: 0.3 mL/min) was used, and UV detection was performed at 240 nm. Liquid–liquid extraction of plasma samples was carried out using dichloromethane. The bioanalytical method was linear over a range of VRC concentrations (100–2000 ng/mL) and OMZ (50–10,000 ng/mL) concentrations, and exhibited both accuracy and precision within the acceptable respective ranges. The average extraction recoveries for VRC and OMZ in plasma were 94.88 % and 82.76 %, respectively. Additionally, the method was successfully applied in vivo to estimate the pharmacokinetic features of VRC in the plasma of rats receiving gavage with low and high doses of OMZ. In conclusion, using a new UHPLC method, we determined that co-administration of OMZ substantially decreased the bioavailability of VRC in rats. Potentially significant drug interactions should be considered in patients receiving the combination of OMZ and VRC.

Development and validation of a reversed-phase HPLC-UV method for simultaneous determination of levosulpiride and omeprazole in human plasma: Applicability of the method for evaluation of pharmacokinetic drug-drug interactions.

Levosulpiride and omeprazole are co-prescribed for gastrointestinal disorders associated with depression and anxiety. Objective of the study was to develop a sensitive, robust and simple method for simultaneous analysis of levosulpiride and omeprazole in human plasma and applicability of the method in determination of pharmacokinetics drug-drug interaction. In the presented study, a reversed-phase HPLC-UV method was developed for the simultaneous determination of levosulpiride and omeprazole using pantoprazole as the internal standard. Experimental conditions were optimized and the developed method was validated as per standard guidelines (USP and ICH). Furthermore, the developed method was applied for evaluation of pharmacokinetics drug-drug interaction between levosulpiride (50 mg) and omeprazole (40 mg) in healthy human volunteers. Sharpsil C8 column (4.6 × 250 mm, 5 μm), Ultisil C8 column (4.6 mm × 150 mm, 5 μm) and Agilent C18 column (4.6 × 250 mm, 5 μm) were evaluated as stationary phase. The best resolution was achieved with Agilent C18 (4.6 x 250 mm, 5 μm) column and was selected for further study. The mobile phase consisted of a mixture of acetonitrile and phosphate buffer (pH 7.2) in 60:40 by volume, and was pumped at a flow rate of 1 mL/min. Detector wavelength was set at 280 nm. Levosulpiride and omeprazole were extracted from human plasma with ethyl acetate and dichloromethane (4:1, v/v). The calibration curves for both levosulpiride (5-150 ng/mL) and omeprazole (10-1500 ng/mL) were linear. The lower limit of quantification and limit of detection for levosulpiride were 5 and 2 ng/mL, while for omeprazole these were 10 and 3 ng/mL, respectively. Pharmacokinetics analysis showed that co-administration of omeprazole increased the AUC and Cmax of levosulpiride, while the clearance was reduced. Both the changes were insignificant. Similarly, no significant change in the pharmacokinetic parameters of omeprazole was observed with co-administration of levosulpiride.

Pharmacokinetics and bioequivalence evaluation of omeprazole and sodium bicarbonate dry suspensions in healthy Chinese volunteers

Omeprazole and sodium bicarbonate dry suspension are effective treatments for acid-related disorders. This study compared the bioequivalence and safety of the two formulations of omeprazole and sodium bicarbonate powder and assessed how CYP2C19 gene polymorphisms affect pharmacokinetics (PK). A single-center, randomized, single-dose, 2-sequence and 2-period crossover method was performed in forty healthy Chinese subjects. Blood samples were collected after a single dose for PK (AUC0–∞, AUC0–t, and Cmax) analysis. The concentrations of Omeprazole in human plasma were determined by HPLC–MS/MS. Besides, the gene polymorphisms of CYP2C19 were assessed by Sanger sequencing. The geometric mean ratios (90% confidence interval) [GMR (95% CI)] of Test/Reference preparation for Cmax: 95.2% (88.48%, 102.43%), AUC0–t: 97.47% (94.4%, 101.02%), AUC0–∞: 97.68% (94.27%, 101.21%) were within the range of 80.00–125.00%. The non-parametric test showed no statistical difference in Tmax between the two groups (p > 0.05). All drugs were well tolerated, no severe adverse reactions occurred, and no significant differences in adverse events between the two drugs. For CYP2C19 gene polymorphisms, the results showed that of 40 subjects, 12 subjects were extensive metabolizers, 24 were intermediate metabolizers, and 4 were poor metabolizers, the frequency of metabolic genotypes were 30%, 60%, and 10%. And the allele distributions for CYP2C19 were *1, *2, and *3 at 60%, 38.75%, and 1.25%. Both the CYP2C19 alleles and metabolic genotypes were consistent with other studies in Chinese. The results of PK parameters showed that different genotypes of CYP2C19 lead to significant differences in t1/2, AUC0–t, AUC0–∞ and Cmax, but no significant differences in Tmax in each group. At the same time, we confirmed that the PK parameters of the test and reference had no differences between the males and females. This study has shown that the pharmacokinetic parameters of the two formulations are not significantly different, which showed bioequivalence and exemplary safety. CYP2C19 gene polymorphism significantly differed in the PK parameters of omeprazole sodium bicarbonate powder.

Effect of Sijunzi Pills on Pharmacokinetics of Omeprazole in Beagle Dogs by HPLC-UV: A Herb-Drug Interaction Study.

A sensitive high-performance liquid chromatography (HPLC-UV) method for determination of omeprazole in beagle dog plasma was developed and to investigate the effect of Sijunzi pills (SJZPs) on the pharmacokinetics of omeprazole in beagle dogs. The beagle dog plasma was extracted with ethyl acetate and n-hexane under alkaline conditions. Omeprazole and internal standard (IS, fluconazole) were separated on an XDB-C18 column, and acetonitrile and 0.1% trifluoroacetic acid were used as the mobile phase. Omeprazole and IS were detected by using a diode array detector. This experiment adopts the experimental design of double-cycle self-control. In the first cycle (group A), six beagle dogs were given omeprazole 0.67 mg/kg orally in a single dose. In the second period (group B), the same six beagle dogs were orally given SJZPs 0.2 g/kg twice a day for 7 consecutive days, and then, omeprazole was orally given. At the different time points after omeprazole was given in the two periods, the blood samples were collected. The concentration of omeprazole was detected by the developed HPLC method. DAS 2.0 was used to calculate the pharmacokinetic parameters of omeprazole. Under the current experimental conditions, this UPLC method showed good linearity in the detection of omeprazole. Interday and intraday precision did not exceed 10%, and the range of accuracy values were from −1.43% to 2.76%. The results of extraction recovery and stability met the requirements of FDA approval guidelines of bioanalytical method validation. The Cmax of omeprazole in group B was 61.55% higher than that in group A, and the AUC(0−t) and AUC(0−∞) of omeprazole in group B were 63.96% and 63.65% higher those that in group A, respectively. At the same time, the clearance (CL) and apparent volume of distribution (Vd) decreased in group B. In this study, an HPLC method for the determination of plasma omeprazole concentration was established. SJZPs could inhibit the metabolism of omeprazole and increase the concentration of omeprazole in beagle dogs. It is suggested that when SJZPs are combined with omeprazole, attention should be paid to the herb-drug interactions and possible adverse reactions.

Profiling and Identification of Omeprazole Metabolites in Mouse Brain and Plasma by Isotope Ratio-Monitoring Liquid Chromatography-Mass Spectrometric Method.

Neuro–inflammation is known to be one of the pathogenesis for the degenerative central nervous system (CNS) disease. Recently various approaches for the treatment of brain diseases by controlling neuro-inflammation in the brain have been introduced. In this respect, there is a continuous demand for CNS drugs, which could be safer and more effective. Omeprazole, a well-known proton-pump inhibitor (PPI) is generally prescribed for the treatment of peptic ulcer. In addition to the anti-gastric acid secretion mechanism, recent studies showed that omeprazole or PPIs would likely have anti-inflammation effects in vitro and in vivo, but their effects on anti-inflammation in brain are still unknown. In this study, omeprazole and its metabolites in a mouse’s brain after various routes of administration have been explored by stable isotope ratio-patterning liquid chromatography–mass spectrometric method. First, a simple liquid chromatography–mass spectrometric (LC–MS) method was established for the quantification of omeprazole in mouse plasma and brain. After that, omeprazole and its stable isotope (D3–omeprazole) were concomitantly administered through various routes to mice in order to identify novel metabolites characteristically observed in the mouse brain and were analyzed using a different LC–MS method with information-dependent analysis (IDA) scan. With this unique approach, several new metabolites of omeprazole were identified by the mass difference between omeprazole and stable isotope in both brain and plasma samples. A total of seventeen metabolites were observed, and the observed metabolites were different from each administration route or each matrix (brain or plasma). The brain pharmacokinetic profiles and brain-to-plasma partition coefficient (Kp) were also evaluated in a satellite study. Overall, these results provide better insights to understand the CNS-related biological effects of omeprazole and its metabolites in vivo.

Simultaneous enantioselective determination of omeprazole, rabeprazole, lansoprazole, and pantoprazole enantiomers in human plasma by chiral liquid chromatography-tandem mass spectrometry.

Proton pump inhibitors, including omeprazole, rabeprazole, lansoprazole, and pantoprazole, achieved simultaneous enantioselective determination in the human plasma by chiral liquid chromatography-tandem mass spectrometry. The four corresponding stable isotope-labeled proton pump inhibitors were adopted as the internal standards. Each enantiomer and the internal standards were extracted with acetonitrile containing 0.1% ammonia, then separated with a Chiralpak IC column (5 µm, 4.6mm × 150mm) within 10 min. The mobile phase was composed of acetonitrile-ammonium acetate (10mM) containing 0.2% acetic acid (50:50, v/v). To quantify all enantiomers, an API 4000 tandem mass spectrometer was used, and multiple reaction monitoring transitions were performed on m/z 360.1→242.1, 384.1→200.1, 370.1→252.1, and 346.1→198.1, respectively. No significant matrix effect was observed for all analytes. The calibration curve for all enantiomers were linear from 1.25 to 2500ng/mL. The precisions for intra- and inter-run were<14.2%, and the accuracy fell in the interval of -5.3 to 8.1%. Stability of samples was confirmed under the storage and processing conditions. The developed method was also suitable for separation and determination of ilaprazole enantiomers. The validated method combining the equilibrium dialysis method was applied to the protein binding ratio studies of four pairs proton pump inhibitor enantiomers in human plasma.

Effects of Naringin on the Activity and mRNA Expression of CYP Isozymes in Rats

Naringin (NRG) is a common dietary flavonoid in citrus fruits and has been documented to possess multiple pharmacological activities, including anti-oxidant, anti-inflammatory, and neuroprotective effects. Naringin is frequently consumed in combination with common clinical drugs. To date, the effects of NRG on cytochrome P450 enzymes have not been fully investigated yet. In this study, the activities of hepatic CYP1A2, CYP2D2, CYP2C9, CYP2C19, and CYP2E1 in rats after the continuous oral administration of NRG (50 and 500 mg/kg) were evaluated using cocktail probe-drug method. The concentrations of 5 probe drugs (phenacetin, dextromethorphan, diclofenac sodium, omeprazole, and chlorzoxazone) in rat plasma were simultaneously determined with a validated HPLC-MS/MS (high performance liquid chromatography-tandem mass spectrometry) method and then used to calculate corresponding pharmacokinetic parameters. Compared with the control group, the AUC(0- t), AUC(0-∞), t 1/2, and C max of each probe drug in treatment groups showed no significant differences. Meanwhile, fluorescence quantitative polymerase chain reaction (FQ-PCR) analysis revealed that NRG did not significantly affect the mRNA expressions of genes CYP1a2, CYP2d2, CYP2c6, CYP2c11, and CYP2e1 in rat liver. Based on these results, it could be concluded that NRG showed no significant effects on the activities and mRNA expressions of tested CYP450 in rats.

Evaluation of a Hollow-Fiber Liquid-Phase Microextraction Technique for the Simultaneous Determination of PPI Drugs in Human Plasma by LC-DAD.

This study involved the development, validation and application of a three-phase hollow-fiber liquid-phase microextraction (HF-LPME) and liquid chromatography with diode array detection (LC-DAD) method for the simultaneous determination of the proton pump inhibitor (PPI) drugs omeprazole, pantoprazole and lansoprazole in human plasma. The evaluation of the HF-LPME parameters was crucial for the determination of the drugs and the conditions selected were: 1-octanol as solvent; phosphate buffer at pH 5 as donor phase; borate buffer at pH 10 as acceptor phase; extraction time of 15 min; stirring at 750 rpm and NaCl was added at 5% (w/v). Validation of the method according to US-FDA recommendations showed a good linear range (0.2-2.0 μg/mL) for all analytes, with a determination coefficient >0.9910. Precision was evaluated using intra- and inter-day assays, which showed relative standard deviations (RSD), <15% for all concentrations, with a limit of quantification (LOQ) of 0.2 μg/mL. Accuracy was also assessed at these concentration levels and was in the range from 80 to 130%. Finally, the sensitive, selective and reproducible HF-LPME/LC-DAD developed method was successfully applied to human plasma samples from patients undergoing therapy with the PPI drugs.

Application of nickel zinc ferrite/graphene nanocomposite as a modifier for fabrication of a sensitive electrochemical sensor for determination of omeprazole in real samples

In the present study, a simple and highly sensitive sensor for the determination of omeprazole based on nickel-zinc ferrite/graphene modified glassy carbon electrode is reported. The morphology and electro analytical performance of the fabricated sensor were characterized with X-ray diffraction spectrometry, Fourier transform infrared spectrometry, scanning electron microscopy, electrochemical impedance spectroscopy, cyclic voltammetry, differential pulse voltammetry and operation of the sensor. Results were compared with those achieved at the graphene modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions, linear response was over the range of 0.03–100.0µmolL−1. The lower detection limit was found to be 0.015µmolL−1. The effect of different interferences on the anodic current response of OMZ was investigated. By measuring the concentrations of omeprazole in plasma and pharmaceutical samples, the practical application of the modified electrode was evaluated. This revealed that the nickel-zinc ferrite/graphene modified glassy carbon electrode shows excellent analytical performance for the determination of omeprazole with a very low detection limit, high sensitivity, and very good accuracy.

Study of the effect of CYP2C19 polymorphisms on omeprazole pharmacokinetics by utilizing validated LC–MS/MS and Real Time-PCR methods

A fully automated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of omeprazole in human plasma. Utilization of 96-well plates and robotic liquid handling workstations, rendered the whole procedure very fast, compared to the manual respective procedure of Liquid-Liquid Extraction (LLE). Sample analysis was performed by reversed phase LC-MS/MS, with positive electrospray ionization, using multiple reaction monitoring (MRM). The method required low plasma volumes and analysis of samples was completed in short run times. It was fully validated and applied to a pharmacokinetic study after per os administration of 20mg tablet formulations of omeprazole. The obtained concentrations were used for the calculation of the basic omeprazole pharmacokinetic parameters. Some variations observed in pharmacokinetic parameters among subjects were attributed to differences of CYP2C19 genotype. Therefore, a novel molecular method was developed in which DNA analysis was conducted by using Real Time-Polymerase Chain Reaction (Real Time-PCR). As source of biological material, Dried Blood Spots (DBS) were utilized, offering an alternative and advantageous strategy for such kind of studies.

AN LC- MS/MS METHOD FOR THE DETERMINATION OF OMEPRAZOLE ON PROTON PUMP INHIBITOR IN HUMAN PLASMA

A sensitive and selective liquid chromatographic method coupled with tandem mass spectroscopy (LC-MS/MS) was developed for the quantification of omeprazole in human plasma. Lansoprazole was used as internal standard with plasma samples, extracted using 10mM ammonium acetate. A centrifuged upper layer was then evaporated and reconstituted with Acetonitrile: mobile phase buffer 70:30%v/v. The reconstructed samples were injected into a C 18 column purospher star 5µ. The mobile phase was composed of ACN: mobile phase buffer (5mm ammonium bicarbonate buffer) in the ratio of 70:30%v/v with flow rate 1.0mL/min. The mass spectrometer was operated using positive ion mode and turbo electro spray ionisation. Nitrogen was used as the nebulizer, curtain, collision and auxiliary gases. Using MS/MS with multiple reactions monitoring (MRM) mode, omeprazole was detected without severe interferences from plasma matrix. Detection of omeprazole in human plasma was accurate and precision. This method has been successfully applied to the study of omeprazole in human specimens Keywords: Proton pump inhibitor, omeprazole, lansoprazole, LC-MS/MS, liquid liquid extraction

Improvement and validation of a high-performance liquid chromatography in tandem mass spectrometry method for monitoring of omeprazole in plasma.

Omeprazole (OME) is a proton pump inhibitor with a 58% bioavailability after a single oral dose. It is subject to marked interindividual variations and significant drug-drug interactions. The authors developed a simple and rapid method based on liquid chromatography in tandem with mass spectrometry with solid phase extraction and isotope-labeled internal standard to monitor plasma levels of OME in pharmacokinetics and drug-drug interaction studies. OME and its internal standard (OME-D3) were eluted with a Zorbax Extend C-18 rapid resolution column (4.6 × 50 mm, 3.5 μm) at 25°C, under isocratic conditions through a mobile phase consisting of 1 mM ammonium acetate, pH 8.5 (55%), and acetonitrile (45%). The flow rate was 0.8 mL/min, and the chromatogram run time was 1.2 minutes. OME was detected and quantified by liquid chromatography in tandem with mass spectrometry with positive electrospray ionization, which operates in multiple-reaction monitoring mode. The method was linear in the range of 1.5-2000 ng/mL for OME. The validation assays for accuracy and precision, matrix effect, extraction recovery, and stability of the samples for OME did not deviate more than 20% for the lower limit of quantification and no more than 15% for other quality controls. These findings are consistent with the requirements of regulatory agencies. The method enables rapid quantification of OME concentrations and can be used in pharmacokinetic and drug-drug interaction studies.

Simultaneous determination of bupropion, metroprolol, midazolam, phenacetin, omeprazole and tolbutamide in rat plasma by UPLC-MS/MS and its application to cytochrome P450 activity study in rats.

A specific ultra-performance liquid chromatography tandem mass spectrometry method is described for the simultaneous determination of bupropion, metroprolol, midazolam, phenacetin, omeprazole and tolbutamide in rat plasma with diazepam as internal standard, which are the six probe drugs of the six cytochrome P450 isoforms CYP2B6, CYP2D6, CYP3A4, CYP1A2, CYP2C19 and CYP2C9. Plasma samples were protein precipitated with acetonitrile. The chromatographic separation was achieved using a UPLC® BEH C18 column (2.1 × 100 mm, 1.7 µm). The mobile phase consisted of acetonitrile and water (containing 0.1% formic acid) with gradient elution. The triple quadrupole mass spectrometric detection was operated by multiple reaction monitoring in positive electrospray ionization. The precisions were <13%, and the accuracy ranged from 93.3 to 110.4%. The extraction efficiency was >90.5%, and the matrix effects ranged from 84.3 to 114.2%. The calibration curves in plasma were linear in the range of 2-2000 ng/mL, with correlation coefficient (r(2) ) >0.995. The method was successfully applied to pharmacokinetic studies of the six probe drugs of the six CYP450 isoforms and used to evaluate the effects of erlotinib on the activities of CYP2B6, CYP2D6, CYP3A4, CYP1A2, CYP2C19 and CYP2C9 in rats. Erlotinib may inhibit the activity of CYP2B6 and CYP3A4, and may induce CYP2C9 of rats.

Simple and Fast Liquid Chromatography–Mass Spectrometry (LC–MS) Method for the Determination of Omeprazole, 5-hydroxyomeprazole, and Omeprazole Sulphone in Human Plasma

A method was developed for the determination of omeprazole, 5-hydroxy-omeprazole, and omeprazole-sulphone in human plasma. The mobile phase with 0.1% formic acid in acetonitrile and 0.1% formic acid in water (40/60 v/v) was used successfully for the first time for the analysis of these analytes. Analysis was carried out using Hichrom RP18 (150 × 3.0 mm, 3 µm. UK) column interfaced with a LTQ Orbitrap mass spectrometer. The calibration range for omeprazole and omeprazole sulphone was 0.002–1 µg/mL, whereas, for 5-hydroxy omeprazole was 0.005–1 µg/mL. The extracted ion ranges ([M + H]+) were; m/z 346.12–346.13 for omeprazole, 362.11–362.12 for 5-hydroxy-omeprazole, and omeprazole-sulphone and 384.07–384.09 for pantoprazole. The regression equation for omeprazole was 0.071x + 0.445, for 5-hydroxy omeprazole was y = 0.08x + 0.017 and for omeprazole sulphone y = 0.007x + 0.05. This method was successfully applied for the determination of pharmacokinetic parameters of omeprazole and its metabolites in human volunteers (n = 20).

A Sensitive Pyrolytic Graphite Sensor for Determination of Omeprazole in Human Blood Plasma and Pharmaceuticals

The electrochemical determination of omeprazole (OMZ), a gastric acid secretion inhibitor, is described using cyclic voltammetry and square wave voltammetry (SWV) at edge plane pyrolytic graphite sensor (EPPGs). A well-defined oxidation peak was observed in SWV as a result of the oxidation of OMZ at ∼828 mV in phosphate buffer of pH 7.2. The peak current increased linearly with the increase of concentration of OMZ in the range 1 μM to 100 μM and detection limit (3 σ/b) and sensitivity were found to be 19 nM and 0.1549 μA μM−1, respectively. The analytical utility of developed protocol was evaluated by performing the recovery experiments in human plasma samples of patients undergoing treatment with OMZ and recovery was found in the range of 98.71–100.82%. The method was successfully used to determine the content of OMZ in enteric-coated tablets of pharmaceutical formulations of different companies and blood plasma of patients undergoing treatment with OMZ. The sensor exhibited good stability and reproducibility with relative standard deviation of ± 2.74% and ± 3.48%, respectively. The method is simple, reliable and precise with good stability and reproducibility.

HPLC Determination of Omeprazole in Human Plasma Using a Monolithic Column

A rapid and sensitive HPLC method using a monolithic column has been developed for quantification of omeprazole (CAS 73590-58-6) in plasma. The method was specific and sensitive with a quantification limit of 10 ng/ml. Sample preparation involves simple, one-step extraction procedure and analytical recovery was complete. The separation was carried out in reversed-phase conditions using a Chromolith Performance (RP-18e, 100 x 4.6 mm) column with an isocratic mobile phase consisting of 0.01 mol/l disodium hydrogen phosphate buffer-acetonitrile (73:27 v/v) adjusted to pH 7.1. The wavelength was set at 302 nm. The calibration curve was linear over the concentration range 20-1500 ng x ml(-1). The coefficients of variation for inter-day and intra-day assay were found to be less than 7%.

OPTIMIZATION AND VALIDATION OF HPLC-UV METHOD FOR SIMULTANEOUS DETERMINATION OF OMEPRAZOLE AND ITS METABOLITES IN HUMAN PLASMA: EFFECTS OF VARIOUS EXPERIMENTAL CONDITIONS AND PARAMETERS

A simple and economical reversed phase HPLC-UV method was developed for omeprazole (OMP) and its two main metabolites, 5-Hydroxy omeprazole (5-OH-OMP) and omeprazole sulfone (OMP-S) in human plasma using pantoprazole as the internal standard. After optimization of various chromatographic conditions and experimental parameters, the method was validated according to standard guidelines. The separation of all the analytes was achieved on a Supelco C18 column using methanol and phosphate buffer (pH 7.2) in the ratio of (42:58, v/v) as the mobile phase in isocratic mode at a flow rate of 0.8 mL/min and wavelength of 302 nm, keeping column oven temperature at 45°C. Extraction of analytes from plasma was achieved through precipitation method followed by injecting a sample volume of 20 µL into the HPLC system. The limits of detection were 3, 1.5, and 1.3 ng/mL and limits of quantification were 10, 5, and 5 ng /mL for 5-0H-OMP, OMP-S, and OMP, respectively. The method was also successfully applied for the determination of S-isomer of omeprazole (esomeprazole) in human plasma.

Simultaneous determination of tolbutamide, omeprazole, midazolam and dextromethorphan in human plasma by LC–MS/MS—A high throughput approach to evaluate drug–drug interactions

Drug–drug interactions involving cytochrome P450 (CYP450s) are an important factor for evaluation of a new chemical entity (NCE) in drug development. To evaluate the potential inhibitory effects of a NCE on the pharmacokinetics of a cocktail of representative probes of CYP enzymes (midazolam for CYP3A4, tolbutamide for CYP2C9, omeprazole for CYP2C19 and dextromethorphan for CYP2D6) and the safety and tolerability of the NCE in the presence of probe substrates, a high throughput liquid chromatography/tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous determination of tolbutamide, omeprazole, midazolam and dextromethorphan in human plasma using tolbutamide-d 9, midazolam-d 4, (±)-omeprazole-d 3, and dextromethorphan-d 3 as the internal standards (ISs). Human plasma samples of 50 μL were extracted by a simple protein-precipitation procedure and analyzed using a high performance liquid chromatography electrospray tandem mass spectrometer system. Reversed-phase HPLC separation was achieved with a Hypersil GOLD AQ column (50 mm × 4.6 mm, 5 μm). MS/MS detection was set at mass transitions of 271 → 172 m/ z for tolbutamide, 346 → 198 m/ z for omeprazole, 326 → 291 m/ z for midazolam, 272 → 171 m/ z for dextromethorphan, 280 → 172 m/ z for tolbutamide-d 9 (IS), 349 → 198 m/ z for (±)-omeprazole-d 3 (IS), 330 → 295 m/ z for midazolam-d 4 (IS), and 275 → 171 m/ z for dextromethorphan-d 3 (IS) in positive mode. The high throughput LC–MS/MS method was validated for accuracy, precision, sensitivity, stability, recovery, matrix effects, and calibration range. Acceptable intra-run and inter-run assay precision (<10%) and accuracy (<10%) were achieved over a linear range of 50–50,000 ng/mL for tolbutamide, 1–1000 ng/mL for omeprazole, 0.1–100 ng/mL for midazolam and 0.05–50 ng/mL for dextromethorphan in human plasma. Method robustness was demonstrated by the 100% pass rate of 24 incurred sample analysis runs and all of the 50 clinical study samples used for incurred sample reproducibility (ISR) test having met the acceptance criterion (%Diff within 20%). The overall ISR results for all compounds showed that over 95% of the samples had a %Diff of less than 10%. The method is simple, rapid and rugged, and has been applied successfully to sample analysis in support of a drug–drug interaction study.

A bio‐analytical hydrophilic interaction LC‐MS/MS method for the simultaneous quantification of omeprazole and lansoprazole in human plasma in support of a pharmacokinetic omeprazole study in children

A hydrophilic interaction LC method with MS/MS was developed and validated for the simultaneous quantification of omeprazole and lansoprazole in human plasma. Chromatographic separation was achieved on a Betasil silica column using a high organic mobile phase (eluent A: ACN/formic acid 997.5:2.5 v/v; eluent B: water/formic acid 997.5:2.5 v/v) and gradient elution. The mass spectrometer was operated in the Multiple Reaction Monitoring mode. Prior to chromatography, liquid-liquid extraction with ethyl acetate was used and the organic layer was diluted with ACN, allowing direct injection on column. The method showed acceptable linearity, high precision (RSD%<10.5%), accuracy (88.9-109.3%) and selectivity in the two concentration ranges studied: 1.5-100 and 5-2000 ng/mL. The LOQ was established at 1.5 and 5 ng/mL for the two concentration ranges. Lack of variability in matrix effects was demonstrated and mean extraction recovery for omeprazole and lansoprazole was determined in the low (56.3-67.7%) and high (45.3-44.3%) concentration range, respectively. Additionally, plasma samples were found to be stable after three freeze-thaw cycles and for at least 15 h after extraction. This assay was successfully applied to a pharmacokinetic omeprazole study in children with cerebral palsy and mental retardation.

Improved HPLC Method for Determination of Four PPIs, Omeprazole, Pantoprazole, Lansoprazole and Rabeprazole in Human Plasma

To develop a simple and rapid HPLC method for measuring of four proton-pump inhibitors (PPIs), omeprazole (OPZ), pantoprazole (PPZ), lansoprazole (LPZ) and rabeprazole (RPZ) concentrations in human plasma. Following a single step liquid-liquid extraction analytes along with an internal standard (IS) were separated using an isocratic mobile phase of phosphate buffer (10 mM)/acetonitrile (53/47, v/v adjusted pH to 7.3 with triethylamine) at flow rate of 1 mL/min on reverse phase TRACER EXCEL 120 ODS-A column at room temperature. Total analytical run time for selected PPIs was 10 min. The assays exhibited good linearity (r(2)>0.99) over the studied range of 20 to 2500 ng/mL for OPZ, 20 to 4000 ng/mL for PPZ, 20 to 3000 ng/mL for LPZ and 20 to 1500 ng/mL for RPZ. The recovery of method was equal or greater than 80% and lower limit of quantification (LLOQ) was 20 ng/mL for four PPIs. Coefficient of variation and error at all of the intra-day and inter-day assessment were less than 9.2% for all compounds. The results indicated that this method is a simple, rapid, precise and accurate assay for determination of four PPIs concentrations in human plasma. This validated method is sensitive and reproducible enough to be used in pharmacokinetic studies and also is time- and cost-benefit when selected PPIs are desired to be analyzed.