High performance liquid chromatography mass spectrometric method for the simultaneous quantification of pravastatin and aspirin in human plasma: Pharmacokinetic application

AbstractA rapid and sensitive liquid chromatography–tandem mass spectrometric (LC–MS/MS) assay method has been developed and fully validated for the simultaneous quantification of pravastatin and aspirin in human plasma. Furosemide was used as an internal standard. Analytes and the internal standard were extracted from human plasma by liquid–liquid extraction technique using methyl tertiary butyl ether. The reconstituted samples were chromatographed on a Zorbax SB-C18 column by using a mixture of 5mM ammonium acetate buffer and acetonitrile (20:80, v/v) as the mobile phase at a flow rate of 0.8mL/min. The calibration curve obtained was linear (r≥0.99) over the concentration range of 0.50–600.29ng/mL for pravastatin and 20.07–2012.00ng/mL for aspirin. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. A run time of 2.0min for each sample made it possible to analyze more than 400 human plasma samples per day. The proposed method was found to be applicable to clinical studies

Mixed-Ligand Complexes of Co(II), Ni(II) And Cu(II) with Mercaptosuccinic Acid And 1, 10-Phenanthroline in Dimethylformamide Media

The ternary systems of Co(II), Ni(II) and Cu(II) complexes with Mercaptosuccinic acid as Primary Ligand and 1, 10-Phenanthroline as Secondary Ligand are investigated. The stability constants of the complexes were determined pH metrically in Dimethylformamide medium at 303K and I = 0.16 mol/L NaCl. The predominant species detected are MLX, ML2X, MLXH and MLX2H. Models containing different numbers of species were refined by using the computer program MINIQUAD75. The best-fit chemical models were arrived at based on statistical parameters. The relative stabilities of the ternary complexes and species distributions of all complexes in solution were evaluated

LC-MS/MS ASSAY FOR IRBESARTAN IN HUMAN PLASMA USING SOLID PHASE EXTRACTION TECHNIQUE: A PHARMACOKINETIC STUDY

Objective: The objective of this research was to develop a novel liquid chromatography/tandem mass spectrometry (LC-MS/MS) method for the determination of irbesartan in human plasma.Methods: An analytical method based on liquid chromatography/tandem mass spectrometry (LC-MS/MS) has been developed and validated for the quantitative determination of irbesartan in human plasma. The method utilizes irbesartan d4 as internal standard (IS). After solid phase extraction (SPE), analyte and the IS were chromato graphed on a C18 columns using a isocratic mobile phase composed of methanol–0.2% formic acid (85:15, v/v) pumped at a flow rate of 0.70 mL/min.Results: Precision and accuracy of the method was determined using five analytical batches in the concentration range of 50.0–9982 ng/ml. All the validation experiments were carried out as per the US FDA guidelines and results met the acceptance criteria.Conclusion: The proposed LC–MS/MS assay method is simple, rapid and enough sensitive for the determination of irbesartan in human plasma. A chromatographic run time set at 2.0 min, thus can analyze more than 300 samples in a day. Also, the proposed method was found to be applicable to clinical studies.Â

SIMULTANEOUS DETERMINATION OF ARTESUNATE AND AMODIAQUINE IN HUMAN PLASMA USING LC-MS/MS AND ITS APPLICATION TO A PHARMACOKINETIC STUDY

Objective: The objective of this research was to develop a simple, rapid and sensitive liquid chromatography/tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of artesunate and amodiaquine in human plasma.Methods: An analytical method based on LC-MS/MS has been developed and validated for the simultaneous determination of artesunate and amodiaquine in human plasma. Isotope-labeled compounds are used as internal standards for the quantification of these drugs. Analytes were extracted from the plasma using solid phase extraction (SPE) technique and chromatographed on a C8 column using an isocratic mobile phase composed of 0.1% ammonia solution and methanol (10:90, v/v). The mobile phase was pumped at a flow rate of 1.00 ml/min. A total of five analytical batches were generated for the calculation of intra-day and inter-day precision and accuracy during the entire course of validation.Results: The assay exhibits excellent linearity in the concentration range of 3.07–305.29 ng/ml for artesunate and 0.30–30.01 ng/ml for amodiaquine. Intra-day and inter-day precision and accuracy results are well within the acceptance limits. All the stability experiments were conducted in plasma samples and in neat samples are complying with the recent US FDA and EMEA guidelines.Conclusion: The proposed LC–MS/MS assay method is simple, rapid and sensitive enough for the simultaneous determination of artesunate and amodiaquine in human plasma. This method was successfully used to quantitate the in-vivo plasma concentrations obtained from a pharmacokinetic study and the results were validated by conducting incurred samples reanalysis (ISR).Â

Wnt/β-Catenin Signaling Pathway Is a Direct Enhancer of Thyroid Transcription Factor-1 in Human Papillary Thyroid Carcinoma Cells

The Wnt/β-catenin signaling pathway is involved in the normal development of thyroid gland, but its disregulation provokes the appearance of several types of cancers, including papillary thyroid carcinomas (PTC) which are the most common thyroid tumours. The follow-up of PTC patients is based on the monitoring of serum thyroglobulin levels which is regulated by the thyroid transcription factor 1 (TTF-1): a tissue-specific transcription factor essential for the differentiation of the thyroid. We investigated whether the Wnt/β-catenin pathway might regulate TTF-1 expression in a human PTC model and examined the molecular mechanisms underlying this regulation. Immunofluorescence analysis, real time RT-PCR and Western blot studies revealed that TTF-1 as well as the major Wnt pathway components are co-expressed in TPC-1 cells and human PTC tumours. Knocking-down the Wnt/β-catenin components by siRNAs inhibited both TTF-1 transcript and protein expression, while mimicking the activation of Wnt signaling by lithium chloride induced TTF-1 gene and protein expression. Functional promoter studies and ChIP analysis showed that the Wnt/β-catenin pathway exerts its effect by means of the binding of β-catenin to TCF/LEF transcription factors on the level of an active TCF/LEF response element at [−798, −792 bp] in TTF-1 promoter. In conclusion, we demonstrated that the Wnt/β-catenin pathway is a direct and forward driver of the TTF-1 expression. The localization of TCF-4 and TTF-1 in the same area of PTC tissues might be of clinical relevance, and justifies further examination of these factors in the papillary thyroid cancers follow-up

The role of acid-base imbalance in statin-induced myotoxicity

Disturbances in acid-base balance, such as acidosis and alkalosis, have potential to alter the pharmacological and toxicological outcomes of statin therapy. Statins are commonly prescribed for elderly patients who have multiple co-morbidities such as diabetes mellitus, cardiovascular and renal diseases. These patients are at risk of developing acid-base imbalance. In the present study, the effect of disturbances in acid-base balance on the inter-conversion of simvastatin and pravastatin between lactone and hydroxy acid forms have been investigated in physiological buffers, human plasma and cell culture medium over pH ranging from 6.8 to 7.8. The effects of such inter-conversion on cellular uptake and myotoxicity of statins were assessed in vitro using C2C12 skeletal muscle cells under conditions relevant to acidosis, alkalosis and physiological pH. Results indicate that the conversion of the lactone forms of simvastatin and pravastatin to the corresponding hydroxy acid is strongly pH-dependent. At physiological and alkaline pH, substantial proportions of simvastatin lactone (~ 87% and 99%, respectively) and pravastatin lactone (~ 98% and 99%, respectively) were converted to the active hydroxy acid forms after 24 hours of incubation at 37 °C. At acidic pH, conversion occurs to a lower extent, resulting in greater proportion of statin remaining in the more lipophilic lactone form. However, pH alteration did not influence the conversion of the hydroxy acid forms of simvastatin and pravastatin to the corresponding lactones. Furthermore, acidosis has been shown to hinder the metabolism of the lactone form of statins by inhibiting hepatic microsomal enzyme activities. Lipophilic simvastatin lactone was found to be more cytotoxic to undifferentiated and differentiated skeletal muscle cells compared to more hydrophilic simvastatin hydroxy acid, pravastatin lactone and pravastatin hydroxy acid. Enhanced cytotoxicity of statins was observed under acidic conditions and is attributed to increased cellular uptake of the more lipophilic lactone or unionized hydroxy acid form. Consequently, our results suggest that co-morbidities associated with acid-base imbalance can play a substantial role in the development and potentiation of statin-induced myotoxicity

Facile Hydrogen Evolution Reaction on WO3Nanorods

Tungsten trioxide nanorods have been generated by the thermal decomposition (450 °C) of tetrabutylammonium decatungstate. The synthesized tungsten trioxide (WO3) nanorods have been characterized by XRD, Raman, SEM, TEM, HRTEM and cyclic voltammetry. High resolution transmission electron microscopy and X-ray diffraction analysis showed that the synthesized WO3nanorods are crystalline in nature with monoclinic structure. The electrochemical experiments showed that they constitute a better electrocatalytic system for hydrogen evolution reaction in acid medium compared to their bulk counterpart

Conjoint Analysis for Marketing Research in Brazil

This article offers a review from 1971 to the present, methods of conjoint analysis approaches that are data collection based on stated preferences or choices by consumers. Thousands of studies have been performed using conjoint analysis, since the introduction of the method in the early 70's This set of methods allows market researchers to study trade-off between the attributes of new products, and is useful for various decisions marketing to product design, pricing and market segmentation. The current set of options conjoint analysis is made by the traditional approach stated preference, the discrete choices techniques (or CBCA choice based conjoint analysis) which are based on choices declared by self-explanatory approach which uses direct elicitation of importance attributes and evaluation levels of the attributes and the adaptive approach (ACA or adaptive conjoint analysis) that involves data collection in stages and adaptive. This article summarizes these methods and their recent developments and presents an application in the Brazilian Market. Given the versatility of the method, there is huge potential for marketing research in Brazil. Essentially, this methodology is alive and growing.&nbsp

Simultaneous determination of atorvastatin, metformin and glimepiride in human plasma by LCâMS/MS and its application to a human pharmacokinetic study

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometric (LCâMS/MS) assay method has been developed and fully validated for the simultaneous quantification of atorvastatin, metformin and glimepiride in human plasma. Carbamazepine was used as internal standard (IS). The analytes were extracted from 200 μL aliquots of human plasma via protein precipitation using acetonitrile. The reconstituted samples were chromatographed on a Alltima HP C18 column by using a 60:40 (v/v) mixture of acetonitrile and 10 mM ammonium acetate (pH 3.0) as the mobile phase at a flow rate of 1.1 mL/min. The calibration curves obtained were linear (r2â¥0.99) over the concentration range of 0.50â150.03 ng/mL for atorvastatin, 12.14â1207.50 ng/mL for metformin and 4.98â494.29 ng/mL for glimepiride. The API-4000 LCâMS/MS in multiple reaction monitoring (MRM) mode was used for detection. The results of the intra- and inter-day precision and accuracy studies were well within the acceptable limits. All the analytes were found to be stable in a battery of stability studies. The method is precise and sensitive enough for its intended purpose. A run time of 2.5 min for each sample made it possible to analyze more than 300 plasma samples per day. The developed assay method was successfully applied to a pharmacokinetic study in human male volunteers. Keywords: Atorvastatin, Metformin, Glimepiride, LCâMS/MS, Human plasma, Pharmacokinetic

Conjoint Analysis para Pesquisa de Marketing no Brasil

This article offers a review from 1971 to the present, methods of conjoint analysis approaches that are data collection based on stated preferences or choices by consumers. Thousands of studies have been performed using conjoint analysis, since the introduction of the method in the early 70's This set of methods allows market researchers to study trade-off between the attributes of new products, and is useful for various decisions marketing to product design, pricing and market segmentation. The current set of options conjoint analysis is made by the traditional approach stated preference, the discrete choices techniques (or CBCA choice based conjoint analysis) which are based on choices declared by self-explanatory approach which uses direct elicitation of importance attributes and evaluation levels of the attributes and the adaptive approach (ACA or adaptive conjoint analysis) that involves data collection in stages and adaptive. This article summarizes these methods and their recent developments and presents an application in the Brazilian Market. Given the versatility of the method, there is huge potential for marketing research in Brazil. Essentially, this methodology is alive and growing. Este artigo oferece uma revisão, de 1971 até a atualidade, dos métodos de conjoint analysis que são abordagens de coleta de dados baseadas em preferências ou escolhas declaradas pelos consumidores. Milhares de estudos foram realizados com o uso de conjoint analysis, desde a introdução do método no início da década de 70. Este conjunto de métodos permite que os pesquisadores de mercado estudem trade-off entre os atributos de novos produtos, sendo útil para várias decisões de marketing com design de produto, apreçamento e segmentação de mercado. O conjunto atual de opções de conjoint analysis é composto pela abordagem tradicional de preferência declarada, pelas técnicas de escolhas discretas (CBCA ou choice based conjoint analysis) que se baseiam em escolhas declaradas, pela abordagem autoexplicativa que usa elicitação direta de importância de atributos e avaliação dos níveis dos atributos e pela abordagem adaptativa (ACA ou adaptive conjoint analysis) que implica em coleta de dados por etapas e adaptativa. Este artigo resume estes métodos e seus desenvolvimentos recentes e apresenta uma aplicação no Mercado brasileiro. Dada a versatilidade do método, existe um enorme potencial para a pesquisa de marketing no Brasil. Essencialmente, esta metodologia está viva e crescendo.&nbsp