Measurement of urinary oxypurinol by high performance liquid chromatography–tandem mass spectrometry

Short-term cold stress can reduce the abundance of antibiotic resistance genes in the cecum and feces in a pig model

Comprehensive studies on the effects of cold stress on antibiotic resistance genes (ARGs) in the intestines and feces remain scarce. In this study, pigs were selected as the animal model and divided into a normal temperature group and a 48-h short-term cold stress group. The ARG profiles in fecal, cecal content and cecal mucosa samples were analyzed. The results showed that the normalized abundance of ARGs in the cecal mucosa samples in the cold stress group was significantly higher than that in the normal temperature group, while the normalized ARG abundances in the fecal and cecal content samples were significantly lower than those in the normal temperature group (P < 0.05). The bacterial community composition (especially Firmicutes) was the major driver impacting the ARG profile and accounted for 32.2% of the variation in the ARG profile, followed by metabolites (especially creatinine and oxypurinol) and mobile genetic elements (MGEs) (especially plasmids and insertion elements). And it was found that creatinine and oxypurinol can reduce the abundance of ARGs and Firmicutes in the in vitro experiment. The results indicate that short-term cold stress can reduce the abundance of ARGs in the cecum and feces of pigs, providing reference data for environmental safety.

Hydrophilic Interaction Liquid Chromatography (HILIC): Latest Applications in the Pharmaceutical Researches

Background:

Significant advances have been occurred in analytical research since the 1970s by Liquid Chromatography (LC) as the separation method. Reverse Phase Liquid Chromatography (RPLC) method, using hydrophobic stationary phases and polar mobile phases, is the most commonly used chromatographic method. However, it is difficult to analyze some polar compounds with this method. Another separation method is the Normal Phase Liquid Chromatography (NPLC), which involves polar stationary phases with organic eluents. NPLC presents low-efficiency separations and asymmetric chromatographic peak shapes when analyzing polar compounds. Hydrophilic Interaction Liquid Chromatography (HILIC) is an interesting and promising alternative method for the analysis of polar compounds. HILIC is defined as a separation method that combines stationary phases used in the NPLC method and mobile phases used in the RPLC method. HILIC can be successfully applied to all types of liquid chromatographic separations such as pharmaceutical compounds, small molecules, metabolites, drugs of abuse, carbohydrates, toxins, oligosaccharides, peptides, amino acids and proteins.

Objective:

This paper provides a general overview of the recent application of HILIC in the pharmaceutical research in the different sample matrices such as pharmaceutical dosage form, plasma, serum, environmental samples, animal origin samples, plant origin samples, etc. Also, this review focuses on the most recent and selected papers in the drug research from 2009 to the submission date in 2020, dealing with the analysis of different components using HILIC.

Results and Conclusion:

The literature survey showed that HILIC applications are increasing every year in pharmaceutical research. It was found that HILIC allows simultaneous analysis of many compounds using different detectors.

Detection of allopurinol and oxypurinol in canine urine by HPLC/MS-MS: Focus on veterinary clinical pharmacokinetics

Allopurinol is the most commonly used drug for the treatment of hyperuricemia in people, and in view of the risks of fatal hypersensitivity in patients with renal dysfunction, doses based on the glomerular filtration rate are proposed. In veterinary medicine, allopurinol is used in the treatment of canine leishmaniasis (CanL) caused by Leishmania infantum owing to the drug action of inhibiting the parasite's RNA synthesis. However, renal dysfunction frequently ensues from disease progression in dogs. The purpose of the present study was to standardize and validate a sensitive high-performance liquid chromatography-mass spectrometric (HPLC-MS/MS) method to determine the concentration of allopurinol and its active metabolite oxypurinol in canine urine for clinical pharmacokinetic investigation. Urine samples of eleven (11) dogs with naturally occurring CanL and in the maintenance phase of the treatment with alopurinol were used. For the chromatographic analysis of urine, the mobile phase consisted of a solution of 0.1 % formic acid (88 %) in 10 mM ammonium acetate. Separation of allopurinol and oxypurinol occurred in a flow of 0.8 mL/min on a C8 reverse phase column 5 μm, and acyclovir was the internal standard. The HPLC-MS/MS method was validated by reaching the limits of detection and quantification, reproducibility and linearity. The lower limit of quantification achieved by the method was 10 μg/mL for both allopurinol and oxypurinol. Calibration curves were prepared in blank urine added with allopurinol at concentrations of 10-1000 μg/mL, and oxypurinol at 10-200 μg/mL. Coefficients of variation of less than 15 % between intracurrent and intercurrent accuracy values were observed for both allopurinol and oxypurinol. Urine test samples remained stable after being subjected to freeze-thaw cycles and remaining at room temperature for 4 h. The method proved to be adequate to quantify allopurinol and oxypurinol in urine samples from dogs under treatment.

Ultra-performance hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry for simultaneous determination of allopurinol, oxypurinol and lesinurad in rat plasma: Application to pharmacokinetic study in rats

A fixed dose combination of lesinurad and allopurinol has been recently approved by USFDA and EMA for treatment of gout-associated hyperuricemia in patients who have not achieved target serum uric acid levels with allopurinol alone. In this study, an ultra-performance hydrophilic interaction liquid chromatography (UPHILIC) coupled with tandem mass spectrometry method was developed and validated for simultaneous determination of allopurinol, oxypurinol and lesinurad in rat plasma. Liquid liquid extraction using ethyl acetate as extracting agent was used for samples extraction procedure. Acquity UPLC HILIC column (100 mm x 2.1, 1.7μm) was used for separation of allopurinol, oxypurinol, lesinurad and internal standard (5-Florouracil). The mobile phase consisting of acetonitrile, water and formic acid (95:5:0.1, v/v/v), were eluted at 0.3 mL/min flow rate having total chromatographic run time of 3 min per sample. The analytes were detected on Acquity triple quadrupole mass spectrometer equipped with a Z-Spray electrospray ionization (ESI). The ESI source was operated in negative mode and multiple reaction monitoring was used for ion transition for all compounds. The precursor to product ion transition of m/z 134.94 > 64.07 for allopurinol, 150.89 > 41.91 for oxypurinol, 401.90 > 176.79 for lesinurad and 128.85 >41.92 for internal standard were used for identification and quantification. The calibration curves for all analytes were found to be linear with weighing factor of 1/x² using regression analysis. The developed assay was successfully applied in an oral pharmacokinetic study of allopurinol, oxypurinol and lesinurad in rats.

Capillary Electrophoresis Hyphenated with Mass Spectrometry for Determination of Inflammatory Bowel Disease Drugs in Clinical Urine Samples

Azathioprine is the main thiopurine drug used in the treatment of immune-based inflammations of gastrointestinal tract. For the purpose of therapy control and optimization, effective and reliable analytical methods for a rapid drug monitoring in biological fluids are essential. Here, we developed a separation method based on the capillary electrophoresis (CE) hyphenated with tandem mass spectrometry (MS/MS) for the simultaneous determination of azathioprine and its selected metabolites (6-thioguanine, 6-mercaptopurine, and 6-methylmercaptopurine) as well as other co-medicated drugs (mesalazine, prednisone, and allopurinol). The optimized CE-MS/MS conditions provided a very efficient and stable system for the separation and sensitive detection of these drugs in human urine matrices. The developed method was successfully applied for the assay of the targeted drugs and their selected metabolites in urine samples collected from patients suffering from inflammatory bowel disease (IBD) and receiving azathioprine therapy. The developed CE-MS/MS method, due to its reliability, short analysis time, production of complex clinical profiles, and favorable performance parameters, evaluated according to FDA guidelines for bioanalytical method validation, is proposed for routine clinical laboratories to optimize thiopurine therapy, estimate enzymatic activity, and control patient compliance with medication and co-medication.

Simultaneous analysis of allopurinol and oxypurinol using a validated liquid chromatography-tandem mass spectrometry method in human plasma

The present study describes a simple, reliable and reproducible liquid chromatography-tandem mass spectrometry method (LC-MS/MS) for the simultaneous determination of allopurinol and its active metabolite, oxypurinol in human plasma for a pharmacokinetic/bioequivalence study. After protein precipitation (PPT) of 100 µL plasma sample with 1.0% formic acid in acetonitrile, the recovery of the analytes and allopurinol-d2 as an internal standard ranged from 85.36% to 91.20%. The analytes were separated on Hypersil Gold (150 mm×4.6 mm, 5 µm) column using 0.1% formic acid-acetonitrile (98:2, v/v) as the mobile phase. Quantification was done using electrospray ionization in the positive mode. The calibration concentration range was established from 60.0 to 6000 ng/mL for allopurinol and 80.0-8000 ng/mL for oxypurinol. Matrix effect in human plasma, expressed as IS-normalized matrix factors ranged from 1.003 to 1.030 for both the analytes. The developed method was found suitable for a clinical study with 300 mg allopurinol tablet formulation in healthy subjects.

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.

Hydrophilic interaction chromatography in drug analysis

Hydrophilic interaction chromatography (HILIC) is an increasingly popular alternative to conventional HPLC for drug analysis. It offers increased selectivity and sensitivity, and improved efficiency when quantifying drugs and related compounds in complex matrices such as biological and environmental samples, pharmaceutical formulations, food, and animal feed. In this review we summarize HILIC methods recently developed for drug analysis (2006–2011). In addition, a list of important applications is provided, including experimental conditions and a brief summary of results. The references provide a comprehensive overview of current HILIC applications in drug analysis.

Pharmacokinetic and Pharmacodynamic Interaction Between Allopurinol and Probenecid in Patients with Gout

Objective.

To investigate the pharmacokinetic and pharmacodynamic interaction between probenecid and oxypurinol (the active metabolite of allopurinol) in patients with gout.

Methods.

This was an open-label observational clinical study. Blood and urine samples were collected to measure oxypurinol and urate concentrations. We examined the effects of adding probenecid to allopurinol therapy upon plasma concentrations and renal clearances of urate and oxypurinol.

Results.

Twenty patients taking allopurinol 100–400 mg daily completed the study. Maximum coadministered doses of probenecid were 250 mg/day (n = 1), 500 mg/day (n = 19), 1000 mg/day (n = 7), 1500 mg/day (n = 3), and 2000 mg/day (n = 1). All doses except the 250 mg daily dose were divided and dosing was twice daily. Estimated creatinine clearances ranged from 28 to 113 ml/min. Addition of probenecid 500 mg/day to allopurinol therapy decreased plasma urate concentrations by 25%, from mean 0.37 mmol/l (95% CI 0.33–0.41) to mean 0.28 mmol/l (95% CI 0.24–0.32) (p < 0.001); and increased renal urate clearance by 62%, from mean 6.0 ml/min (95% CI 4.5–7.5) to mean 9.6 ml/min (95% CI 6.9–12.3) (p < 0.001). Average steady-state plasma oxypurinol concentrations decreased by 26%, from mean 11.1 mg/l (95% CI 5.0–17.3) to mean 8.2 mg/l (95% CI 4.0–12.4) (p < 0.001); and renal oxypurinol clearance increased by 24%, from mean 12.7 ml/min (95% CI 9.6–15.8) to mean 16.1 ml/min (95% CI 12.0–20.2) (p < 0.05). The additional hypouricemic effect of probenecid 500 mg/day appeared to be lower in patients with renal impairment.

Conclusion.

Coadministration of allopurinol with probenecid had a significantly greater hypouricemic effect than allopurinol alone despite an associated reduction of plasma oxypurinol concentrations. Australian Clinical Trials Registry ACTRN012606000276550.