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Copyright of Turkish Journal of Biochemistry / Turk Biyokimya Dergisi is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Turkish Journal of Biochemistry / Turk Biyokimya Dergisi is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Primary Sjögren's syndrome (pSS) is an autoinflammatory disease characterized by inflammation of the exocrine glands. Elevated inflammation causes an increase in kynurenine pathway (KP) metabolite levels by activating indoleamine 2,3-dioxygenase (IDO). The aim of this study was to measure serum KP metabolite concentrations in patients with pSS and to evaluate the relationship between these metabolites with disease activity score and clinical manifestations. A total of 80 patients with pSS and 80 healthy controls were enrolled in this study. Serum tryptophan (TRP), kynurenine (KYN), kynurenic acid (KYNA), 3-hydroxyanthranilic acid (3HAA), 3-hydroxykynurenine (3HK), quinolinic acid (QUIN) concentrations were quantified with liquid chromatography with tandem mass spectrometry (LC-MS/MS). Demographic characteristics, clinical manifestations and disease activity score (ESSDAI) of the participants were recorded. The serum level of KYN and QUIN were significantly higher in patients with pSS with low and moderate activity compared those healthy controls, while the serum level of TRP, KYNA/KYN and 3HK/KYN were lower. In addition, the significant difference for the serum level of KYNA was only in patients with moderate activity from healthy controls, and the difference was higher in favor of pSS patients. Moreover, the KYN/TRP levels were significantly increased with disease activity. The ESSDAI score was positively correlated with KYN/TRP ratio, but negatively correlated with KYNA/KYN ratio. These findings indicated that KP metabolites may play a role in the etiopathogenesis, activation and progression of pSS. [ABSTRACT FROM AUTHOR]

• An LC–MS / MS method was developed for carbamazepine and epoxy metabolite. • The method was validated and found to be accurate, precise and robust. • The Emit® 2000 immunoassay and the LC–MS / MS measurement results were consistent. • Serum electrolyte levels decreased in patients using carbamazepine. • Carbamazepine significantly affected hemogram parameters. The study aimed to develop a validated LC–MS / MS method for the measurement of carbamazepine and carbamazepine-10,11-epoxide (CBZE) levels, to compare the carbamazepine concentrations measured by AbSciex API 3200 LC–MS/MS and Beckman Coulter Emit® 2000 immunoassay and to investigate the effect of carbamazepine concentrations on various hematological and biochemical parameters. For the measurement of carbamazepine and CBZE levels, a validated LC–MS / MS method was developed. Serum carbamazepine levels of patients were measured by AbSciex API 3200 LC–MS / MS and Beckman Coulter Emit® 2000 immunoassay. Biochemical, hematological parameters, and hormone levels were measured by Beckman-Coulter AU 5800 (Beckman Coulter, Brea, USA), Beckman Coulter LH 780 (Beckman Coulter, Miami, FL, USA), and Cobas 6000 (Roche Diagnostics, Germany) analyzers, respectively. The imprecision values for all analytes were less than 7.0 %. The correlation coefficient between the methods was 0.981 (95 % confidence interval: 0.975 to 0.985). Linear regression analysis demonstrated highly significant associations of carbamazepine concentrations with albumin (B = −0.300, p = 0.040), calcium (B = −0.262, p = 0.004), phosphorus (B = −0.241, p = 0.022), WBC (B = −0.288, p = <0.001), PLT (B = −0.236, p = 0.003), RBC (B = −0.257, p = 0.001), NEU% (B = −0.289, p = <0.001), LYM% (B = −0.268, p = 0.001), D vitamini (B = −0.344, p = 0.006) levels. A robust, rapid, and simple method has been developed. Our study revealed that carbamazepine and its metabolite have a significant correlation and likely impact on bone metabolism, blood cell counts, serum protein, albumin levels, and electrolyte concentrations. [ABSTRACT FROM AUTHOR]

• Positive and negative LC- MS / MS methods were developed for favipiravir. • Inter-assay precisions were less than 8.0% in both modes. • Total run time was 3.5 min. • Simple pretreatment step based on protein precipitation only was the main advantage. • The method was successfully applied for COVID-19 patients receiving favipiravir. Favipiravir is a broad-spectrum inhibitor of viral RNA polymerase. It is currently used as a possible treatment for coronavirus disease 2019 (COVID-19). Pre-clinical or clinical trials of favipiravir require robust, sensitive, and accurate bioanalytical methods for quantitation of favipiravir levels. Recently, several studies have been reported about developing a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for measuring favipiravir levels. However, these methods were validated predominantly for plasma samples, electrospray ionization was operated only in negative or positive mode, and clinical application of these methods has not been applied for patients with COVID-19. This study aimed was to develop a validated LC-MS/MS method for the measurement of favipiravir levels in positive and negative electrospray ionization mode and to perform a pilot study in patients with COVID-19 receiving favipiravir to demonstrate the applicability of this method in biological samples. Simple protein precipitation was used for the extraction of favipiravir from the desired matrix. Favipiravir levels were quantitated using MS / MS with an electrospray ionization source in positive and negative multiple reaction monitoring (MRM) mode. The chromatographic detection was performed on a reverse-phase Phenomenex C18 column (50 mm × 4.6 mm, 5 µm, 100 Å) with gradient elution using 0.1% formic acid in water and 0.1% formic acid in methanol as mobile phase. The method was linear over the concentration ranges of 0.048–50 µg/mL (in negative ionization mode) and 0.062–50 µg/mL (in positive ionization mode) with a correlation coefficient (r2) better than 0.998. The total run time was 3.5 min. The intra-assay and inter-assay %CV values were less than 7.2% and 8.0%, respectively. A simple, rapid and robust LC-MS / MS method was developed for the measurement of favipiravir and validation studies were performed. The validated method was successfully applied for drug level measurement in COVID-19 patients receiving favipiravir. [ABSTRACT FROM AUTHOR]

• The LC–MS/MS method is robust, fast, simple and cost-effective. • Norclozapine and clozapine-N -oxide were also determined by this method. • Serum lipid and glucose levels increased in patients using clozapine. • Serum clozapine levels were positively correlated with total cholesterol levels. • Serum clozapine levels were negatively correlated with hemoglobin levels. Clozapine is one of the most effective drugs for resistant schizophrenia, but its severe metabolic and hematological side effects limit the use of clozapine. It has been reported that clozapine blood concentrations should be maintained between 350−600 ng/mL. Our aim was to develop a determination method for clozapine and its main metabolites norclozapine and clozapine -N- oxide, to perform validation studies and to investigate the change of various biochemical parameters in patients using clozapine. A liquid chromatography-tandem mass spectrometry (LC–MS/MS) method was developed and validated for clozapine measurement. Thus, blood samples were collected from 38 patients with schizophrenia and 32 healthy volunteers. Biochemical and hematological parameters were measured by Beckman-Coulter AU 5800 (Beckman Coulter, Brea, USA) and Beckman Coulter LH 780 analyzer (Beckman Coulter, Miami, FL, USA), respectively. Hormone levels were analyzed using Cobas 6000 analyzer (Roche Diagnostics, Germany). The LC MS/MS method was linear between 1.22−2500 ng/mL (r2 = 0.9971) for clozapine. The retention times of clozapine, norclozapine and clozapine -N- oxide were 0.92, 0.89 and 0.95, respectively. Blood glucose (GLU) (p = 0.025), low density lipoprotein (LDL-cholesterol) (p = 0.015), triglyseride (TG) (p = 0.042) and total cholesterol (TC) (p = 0.024) levels were higher; hemoglobin (HGB) (0.015), mean corpuscular hemoglobin (MCH) (0.036), red blood cell count (RBC) (0.020), neutrophil (NEU) (0.034), and platelet (PLT) (P = 0.005) levels were lower in the clozapine group. This LC–MS/MS method was rapid, simple, cost-effective and suitable for the routine clozapine monitoring. Furthermore, norclozapine and clozapine -N- oxide were also determined. Monitoring of metabolic and hematological parameters with clozapine levels is very important. However, the limitations of the study were that the method was not validated for norclozapine and clozapine -N- oxide, so the validation parameters were not evaluated for these two metabolites. [ABSTRACT FROM AUTHOR]