Identification, isolation, and synthesis of seven novel impurities of anti-diabetic drug Repaglinide.

Seven unknown impurities in Repaglinide bulk drug batches at below 0.1% (ranging from 0.05 to 0.10%) were detected by an ultra-performance liquid chromatographic (UPLC) method. These impurities were isolated from the crude sample of Repaglinide using preparative high performance liquid chromatography (prep-HPLC). Based on liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI/MS) study, the chemical structures of seven new impurities (8, 9, 10, 11, 13, 14, and 16) were presumed and characterized as 4-(cyanomethyl)-2-ethoxybenzoic acid (8), 4-(cyanomethyl)-2-ethoxy-N-(3-methyl-1-(2-(piperidin-1-yl)phenyl)butyl)benzamide (9), 4-(2-amino-2-oxoethyl)-2-ethoxy-N-(3-methyl-1-(2-(piperidin-1-yl)phenyl)butyl) benzamide (10) and 2-(3-ethoxy-4-((3-methyl-1-(2-(piperidin-1-yl)phenyl)butyl) carbamoyl) phenyl) acetic acid (11) and 4-(cyanomethyl)-N-cyclohexyl-2-ethoxybenzamide (13), 2-(4-(cyclohexylcarbamoyl)-3-ethoxyphenyl) acetic acid (14) and N-cyclohexyl-4-(2-(cyclohexylamino)-2-oxoethyl)-2-ethoxybenzamide (16). The complete spectral analysis, proton nuclear magnetic resonance (1 H NMR), 13 C NMR, MS, and infrared (IR) confirmed the proposed chemical structures of impurities. Identification, structural characterization, formation, and their synthesis was first reported in this study. The impurity 11 was crystallized and structure was solved by single crystal X-ray diffraction. Copyright © 2017 John Wiley & Sons, Ltd.

Synthesis and biological evaluation of novel N1-phenylsulphonyl indole derivatives as potent and selective 5-HT6R ligands for the treatment of cognitive disorders.

A series of 1-[3-(4-methyl piperazin-1-ylmethyl) phenylsulfonyl]-1H-indole and 1-[3-(4-ethyl piperazin-1-ylmethyl) phenylsulfonyl]-1H-indole derivatives were designed and synthesized as 5-HT6 receptor (5-HT6R) ligands. The lead compound 1-[4-methyl-3-(4-methyl piperazin-1-yl methyl) phenylsulfonyl]-1H-indole dihydrochloride (6b), in this series, has shown potent in vitro binding affinity, selectivity, good pharmacokinetics (PK) profile and activity in the animal models of cognition.

Preparation, characterization, and in vivo evaluation of valsartan porous matrices using emulsion solvent evaporation technique.

INTRODUCTION: Valsartan is a type II Biopharmaceutics Classification System (BCS) classified drug. The poor aqueous solubility restricts its use in developing sustained or controlled release systems for the treatment of chronic hypertensive conditions. The present investigation was conducted with an objective to formulate porous matrices (PMs) of valsartan in order to enhance aqueous solubility. MATERIALS AND METHODS: Polyvinylpyrrolidone (PVP) K30 and poloxamer 407 were used as hydrophilic carriers; hexane was used as a pore-forming agent, ethanol was used as a solvent, and tween 20 was used as an emulgent. The prepared porous matrices were characterized and based on the maximum slope obtained from the Washburn method and other characterization results; the drug PVP K30 (1:1.5) was selected and further evaluated in vivo by the rat gut method. RESULTS: The prepared porous matrices are white, free-flowing powders. Among prepared formulations drug PVP K30 (1:1.5) showed maximum Washburn slope of 0.0103. The mean particle size was found to be 0.82 µ and D50 (median) value was found to be 0.55 µ. The scanning of particles at various magnifications by scanning electron microscopy (SEM) analysis revealed that the method had effectively induced porosity. The Q value of valsartan from porous matrices was observed at 20 min with a first order regression value of 0.917. The calculated difference factor (F1) when compared with pure valsartan was observed to be 63.32%. From the values obtained, it was evident that the method amplifies the percentage of drug dissolution between sixfold and eightfold when compared to pure drug. From the absorption studies by the rat gut method, the absorption of porous matrices increased threefold. CONCLUSION: Porous matrices of valsartan: PVP K30 (1:1.5 ratio) hold promise for the enhancement of solubility and consecutive formulation of controlled release systems even with poorly soluble drugs.

Design, synthesis and pharmacological evaluation of indolylsulfonamide amines as potent and selective 5-HT6 receptor antagonists.

A series of N'-[3-(indole-1-sulfonyl) aryl]-N,N-dimethyl ethane-1,2-diamines and N'-[3-(indole-1-sulfonyl) aryl]-N,N-dimethyl propane-1,3-diamines was designed and synthesized as 5-HT6 receptor ligands. These compounds, when screened in a functional reporter gene-based assay, displayed potent antagonistic activity with Kb values in the range of 1.8-60 nM. The lead compound 9y has shown good ADME surrogate properties, acceptable pharmacokinetic profile and is active in animal models of cognition like novel object recognition test and Morris water maze. It was selected for detailed profiling.

Bioequivalance and pharmacokinetic study of febuxostat in human plasma by using LC-MS/MS with liquid liquid extraction method.

A bioequivalence study was proved of generic Febuxostat 80 mg tablets (T) in healthy volunteers.For this purpose, Authors developed a simple, sensitive, selective, rapid, rugged and reproducible liquid chromatography-tandem mass spectrometry method for the quantification of Febuxostat (FB) in human plasma using Febuxostat D7 (FBD7) as an internal standard (IS) was used. Chromatographic separation was performed on Ascentis Express C18 (50x4.6 mm, 3.5 µ) column. Mobile phase composed of 10 mM Ammonium formate: Acetonitrile (20:80 v/v), with 0.8 mL/min flow-rate. Drug and IS were extracted by Liquid- liquid extraction. FB and FBD7 were detected with proton adducts at m/z 317.1→261.1 and 324.2→262.1 in multiple reaction monitoring (MRM) positive mode respectively. The method was validated with the correlation coefficients of (r(2)) ≥ 0.9850 over a linear concentration range of 1.00-8000.00 ng/mL. This method demonstrated intra and inter-day precision within 2.64 to 3.88 and 2.76 to 8.44% and accuracy within 97.33 to 99.05 and 100.30 to 103.19% for FB. This method is successfully applied in the Bioequivalence study of 9 human volunteers.

Bioanalytical method development and validation of milnacipran in rat plasma by LC-MS/MS detection and its application to a pharmacokinetic study.

A simple, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of milnacipran (MC) in rat plasma by using the liquid-liquid extraction method. Milnacipran-d10 (MCD10) was used as an internal standard (IS). Chromatographic separation was achieved on Zorbax SB-CN (4.6 mm×75 mm, 3.5 µm) column with an isocratic mobile phase composed of 10 mM ammonium acetate (pH 4.0) and methanol in the ratio of 25:75(v/v), at a flow-rate of 0.7 mL/min. MC and MCD10 were detected with proton adducts at m/z 247.2→230.3 and m/z 257.2→240.4 in multiple reaction monitoring (MRM) positive mode respectively. The method was validated over a linear concentration range of 1.00-400.00 ng/mL with a correlation coefficient (r2)≥0.9850. This method demonstrated intra- and inter-day precision within 5.40-10.85% and 4.40-8.29% and accuracy within 97.00-104.20% and 101.64-106.23%. MC was found to be stable throughout three freeze-thaw cycles, bench top and postoperative stability studies. This method was successfully applied to a pharmacokinetic study of rats through i.v. administration.

Design, synthesis and pharmacological evaluation of 4-(piperazin-1-yl methyl)-N1-arylsulfonyl indole derivatives as 5-HT6 receptor ligands.

4-(Piperazin-1-yl methyl)-N(1)-arylsulfonyl indole derivatives were designed and synthesized as 5-HT(6) receptor (5-HT(6)R) ligands. The lead compound 6a, from this series shows potent in vitro binding affinity, good PK profile, no CYP liabilities and activity in animal models of cognition.

Simultaneous Determination of Celecoxib, Erlotinib, and its Metabolite Desmethyl-Erlotinib (OSI-420) in Rat Plasma by Liquid chromatography/Tandem Mass Spectrometry with Positive/Negative Ion-Switching Electrospray Ionisation.

A new method for the simultaneous determination of celecoxib, erlotinib, and its active metabolite desmethyl-erlotinib (OSI-420) in rat plasma, by liquid chromatography/tandem mass spectrometry with positive/negative ion-switching electrospray ionization mode, was developed and validated. Protein precipitation with methanol was selected as the method for preparing the samples. The analytes were separated on a reverse-phase C(18) column (50mm×4.6mm i.d., 3µ) using methanol: 2 mM ammonium acetate buffer, and pH 4.0 as the mobile phase at a flow rate 0.8 mL/min. Sitagliptin and Efervirenz were used as the internal standards for quantification. The determination was carried out on a Theremo Finnigan Quantam ultra triple-quadrupole mass spectrometer, operated in selected reaction monitoring (SRM) mode using the following transitions monitored simultaneously: positive m/z 394.5→278.1 for erlotinib, m/z 380.3→278.1 for desmethyl erlotinib (OSI-420), and negative m/z -380.1→ -316.3 for celecoxib. The limits of quantification (LOQs) were 1.5 ng/mL for Celecoxib, erlotinib, and OSI-420. Within- and between-day accuracy and precision of the validated method were within the acceptable limits of < 15% at all concentrations. The quantitation method was successfully applied for the simultaneous estimation of celecoxib, erlotinib, and desmethyl erlotinib in a pharmacokinetic study in Wistar rats.

Profile of antibiotic consumption, sensitivity and resistance in an urban area of Andhra Pradesh, India.

INTRODUCTION: Antibiotics are an important category of drugs in which indiscriminate use can affect the susceptibility patterns among infectious organisms, resulting in antibiotic resistance. METHODS: Data on antibiotic usage and susceptibility patterns were collected from public and private health centres in Vijayawada, Andhra Pradesh, India, through the use of questionnaires. The data collected were then coded, tabulated, computed and evaluated using statistical analysis. RESULTS: The consumption profile of the different categories of drugs used in public and private hospitals was as follows: nutrition and metabolism products 19.0%; gastrointestinal disorder-related drugs 18.5%; antibiotics 16.8%; anti-pyretics and anti-analgesics 20.6%. These drugs were found to be in high demand. Among the antibiotics, aminoglycosides (amikacin), quinolones (ofloxacin, ciprofloxacin), tetracyclines (doxycycline), penicillin (ampicillin) and sulphonamides (co-trimoxazole) were the most commonly prescribed drugs for antibiotic therapy. 46% of the culture laboratory reports were positive with the following organism profile: Escherichia coli (36%), Klebsiella pneumoniae (16%), Staphylococcus aureus (29%), Enterococcus faecalis (9%) and Pseudomonas aeruginosa (10%). In terms of the sensitivity profile of antibacterials, amikacin (66.9%) was the only antibiotic showing sensitivity patterns, while the majority of antibiotics, such as cotrimoxazole, nalidixic acid, amoxicillin, gentamycin and norfloxacin, had acquired a resistance rate of 55.1%-80.6%. CONCLUSION: The results of this study suggest that indiscriminate prescription and consumption of new broad-spectrum antibiotics against sensitive organisms results in the development of antimicrobial resistance. Therefore, there is an urgent need to curb the excessive use of antibiotics in local hospitals in order to control the trend of increasing antimicrobial resistance to antibiotics.

Simple and sensitive stability-indicating ion chromatography method for the determination of cyclopropylamine in nevirapine and moxifloxacin hydrochloride drug substances.

A simple and sensitive ion chromatography method has been developed for the determination of cyclopropylamine (CPA) in nevirapine (NEV) and moxifloxacin HCl (MOX) pharmaceutical drug substances. Efficient chromatographic separation was achieved on a Metrosep C4, 5 µm (250 mm × 4.0 mm) column. The mobile phase consists of 5 mM hydrochloric acid containing 10% (v/v) acetonitrile and was delivered in an isocratic mode at a flow rate of 0.9 mL min(-1) at 27°C. A conductometric detector was used for the detection of the analyte. The drug substances were subjected to stress conditions including oxidation, thermal, photolytic and humidity for the evaluation of the stability-indicating nature of the method. The method was validated for specificity, precision, linearity, accuracy and solution stability. The limit of detection (LOD) and limit of quantification (LOQ) values are 0.10 µg mL(-1) and 0.37 µg mL(-1) respectively. The linearity range of the method is between 0.37 µg mL(-1) and 1.5 µg mL(-1) and the correlation coefficient is found to be 0.9971. The average recoveries of CPA in NEV and MOX are 97.0% and 98.0%, respectively.

Method development and validation of montelukast in human plasma by HPLC coupled with ESI-MS/MS: application to a bioequivalence study.

A simple, sensitive, and specific LC-ESIâMS/MS method for quantification of Montelukast (MO) in human plasma using Montelukast-d(6) (MOD6) as an internal standard (IS) is discussed here. Chromatographic separation was performed on YMC-pack pro C(18), 50 x 4.6 mm, S-3 Îm column with an isocratic mobile phase composed of 10mM ammonium formate (pH 4.0):acetonitrile (20:80 v/v), at a flow-rate of 0.8 mL min(â1). MO and MOD6 were detected with proton adducts at m/z 586.2â568.2 and 592.3â574.2 in multiple reaction monitoring (MRM) positive mode respectively. MO and MOD6 were extracted using acetonitrile as precipitating agent. The method was validated over a linear concentration range of 1.0â800.0 ng mL(â1) with correlation coefficient (r(2)) â 0.9996. The intraday precision and accuracy were within 1.91â7.10 and 98.32â99.17. The inter-day precision and accuracy were within 3.42â4.41% and 98.14â99.27% for MO. Both analytes were found to be stable throughout three freeze-thawing cycles, bench top, and autosampler stability studies. This method was utilized successfully for the analysis of plasma samples following oral administration of MO (5 mg) in 31 healthy Indian male human volunteers under fasting conditions.

Synthesis and cytotoxicity evaluation of novel 1,4-disubstituted 1,2,3-triazoles via CuI catalysed 1,3-dipolar cycloaddition.

A facile and highly efficient method for the regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles (ß-keto 1,2,3-triazoles) in good to excellent yields from in-situ generated ß-ketoazides and terminal alkynes through Cu(I) catalyzed 1,3 dipolar cycloaddition is described. This reaction proceeds smoothly either in water or in a 1:1 mixture of water and acetone at room temperature without use of any additive. The synthesized compounds were screened for their cytotoxicity in A549 (Lung Cancer), HT-29 (Colon Cancer), He La (Cervical Cancer) using MTT assay that exhibited significant cytotoxicity at modest doses.

Quantitative estimation of riluzole in human plasma by LC-ESI-MS/MS and its application to a bioequivalence study.

A novel simple, sensitive, selective, and rapid high-performance liquid chromatography coupled with tandem mass spectrometry method was developed and validated for quantification of riluzole in human plasma. The chromatography was performed by using a Zorbax-SB-C18 (4.6 x 75 mm, 3.5 microm) column , isocratic mobile phase 0.1% formic acid/acetonitrile (10:90 v/v), and an isotope-labeled internal standard (IS), [(13)C,(15)N(2)]riluzole. The extraction of drug and internal standard was performed by liquid-liquid extraction and analyzed by MS in the multiple reaction monitoring (MRM) mode using the respective [M+H](+) ions, m/z 235.0/165.9 for riluzole and m/z 238.1/169.0 for the IS. The calibration curve was linear over the concentration range 0.5-500.0 ng/ml for riluzole in human plasma. The limit of quantification (LOQ) was demonstrated at 0.5 ng/ml. The within-batch and between-batch precision were 0.6-2.3% and 1.4-5.7%, and accuracy was 97.1-101.1% and 98.8-101.2% for riluzole respectively. Drug and IS were eluted within 3.0 min. The validated method was successfully applied in a bioequivalence study of riluzole in human plasma.

Transdermal therapeutic system of isradipine: effect of hydrophilic and hydrophobic matrix on in vitro and ex vivo characteristics.

Isradipine (ISDP) is an effective calcium channel blocker used in the treatment of hypertension. It undergoes extensive first pass metabolism and bioavailability through the oral route is only about 15 to 24%. Hence we attempted to develop a matrix type controlled transdermal drug delivery system for ISDP. Formulations A1, A2, A3 were composed of Eudragit RL100 and hydroxypropyl methyl cellulose (HPMC) in 1:3, 1:1, 3:1 ratios; A4, A5, A6 were composed of Eudragit RS100 and HPMC in 1:3, 1:1, 3:1 ratios. All six formulations carried 5 mg of ISDP/patch area, 5% v/w of D-limonene, 15 % v/w of propylene glycol in methanol:dichloromethane (1:1). The physicochemical compatibility of the drug and the polymers was studied by infrared spectroscopy and differential scanning calorimetry. The results suggested no physicochemical incompatibility between the drug and the polymers. The prepared transdermal drug delivery system were evaluated for physicochemical characteristics, mainly in vitro release and ex vivo permeation. The ex vivo permeation studies were carried out across excised rat skin using Franz diffusion cell. All the formulations exhibited satisfactory physicochemical characteristics. Cumulative amount of the drug released in 36 h from the six formulations were 1695.32, 1527.89, 1455.54, 1485.65, 1282.81 and 916.88 microg/cm(2) respectively. Corresponding values for the cumulative amounts of drug permeated across the rat skin for the above matrix films were 1456.29, 1284.70, 1182.99, 1212.72, 1046.05, and 782.60 microg/cm(2) respectively. By fitting the data into zero order, first order and Higuchi models, it was concluded that drug release from matrix films followed Higuchi model and the mechanism of drug release was diffusion mediated. Based on the physical evaluation, in vitro drug release and ex vivo permeation characteristics, it was concluded that for potential therapeutic use, monolithic drug matrix films A1, may be suitable for the development of a transdermal drug delivery system of ISDP.

Development and validation of a sensitive bioanalytical method for the quantitative estimation of pantoprazole in human plasma samples by LC-MS/MS: application to bioequivalence study.

The present study aims at developing a simple, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of pantoprazole sodium (PS) in human plasma using pantoprazole D3 (PSD3) as internal standard (IS). Chromatographic separation was performed on Zorbax SB-C18, 4.6 mm x 75 mm, 3.5 microm, 80 A column with an isocratic mobile phase composed of 10 mM ammonium acetate (pH 7.10): acetonitrile (30:70, v/v), pumped at 0.6 mL/min. PS and PSD3 were detected with proton adducts at m/z 384.2-->200.1 and 387.1-->203.1 in multiple reaction monitoring (MRM) positive mode, respectively. Precipitation method was employed in the extraction of PS and PSD3 from the biological matrix. This method was validated over a linear concentration range of 10.00-3000.00 ng/mL with correlation coefficient (r) > or = 0.9997. Intra- and inter-day precision of PS were found to be within the range of 1.13-1.54 and 1.76-2.86, respectively. Both analytes were stable throughout freeze/thaw cycles, bench top and postoperative stability studies. This method was successfully utilized in the analysis of blood samples following oral administration of PS (40 mg) in healthy human volunteers.

Matrix-type transdermal drug delivery system of trandolapril: in vitro and ex vivo characterization.

The purpose of the investigation was to develop and evaluate matrix-type transdermal drug delivery systems (TDDSs) of trandolapril. Matrix-type TDDSs of trandolapril were prepared by solvent evaporation technique. Eight formulations (composed of Eudragit RL 100 and Hydroxypropyl methyl cellulose 15 cps at a ratios of 2:8, 4:6, 6:4, 8:2 in formulations A1, A2, A3, A4; and Eudragit RS 100 and Hydroxypropyl methyl cellulose 15 cps in the same ratios in formulations B1, B2, B3, B4, respectively) were prepared. All formulations contained 5% w/w menthol as penetration enhancer and 15% w/w propylene glycol as plasticizer in ethanol as solvent. The prepared TDDSs were evaluated for physicochemical characteristics, in vitro release and ex vivo permeation. The physicochemical interactions between trandolapril and polymers were investigated by Fourier transform infrared spectroscopy. The results suggested that there is no physicochemical interaction between drug and polymers. The maximum drug release in 24 h for A series formulations was 95.45% (A1), 95.82% (A2), and it was 95.26% (B1), 95.69% (B2) for B series formulations, which are significantly (P < 0.05) different than the lowest values 78.79% (A3), 66.9% (A4) and 82.64% (B3), 71.67% (B4). The formulations A1 (flux 25.03 ± 0.98 µg/cm(2)/h) and B1 (flux 24.62 ± 0.63 µg/cm(2)/h) showed maximum skin permeation in the respective series. The flux obtained with formulations A1 and B1 meets the required flux (37.04 µg/h/cm(2)) with a minimum patch area (3.9 cm(2)). Matrix-type transdermal therapeutic systems of trandolapril could be prepared with the required flux using menthol as penetration enhancer.