Enantioselective determination of R-(-)-manidipine and S-(+)-manidipine in human plasma by a sensitive and selective chiral LC-MS/MS assay.

A sensitive and selective liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay method has been developed and validated for the enantioselective determination of manidipine in human plasma using isotope-labeled compounds as internal standards. After solid-phase extraction, R-(-)-manidipine and S-(+)-manidipine were chromatographed on a Chiralpack IC-3 C18 column using a isocratic mobile phase composed of 2 mm ammonium bicarbonate and acetonitrile (15:85, v/v). The precursor ion to product ion transitions for the enantiomers and internal standards were monitored in the multiple reaction monitoring and positive ionization mode using an API-4000 mass spectrometer. The method was linear over the concentration range of 0.05-10.2 ng/mL for both enantiomers. The precision and accuracy results over five concentration levels in five different batches were well within the acceptance limits. The mean extraction recovery was >80% for both enantiomers. A variety of stability tests were executed in plasma and in neat samples, which complies with the FDA guidelines. After complete validation, the method was successfully applied to a pharmacokinetic study of a manidipine 20 mg oral dose in 10 healthy South India subjects under fasting conditions. The assay reproducibility is shown through incurred samples reanalysis of 20 subject plasma samples.

Highly Efficient Synthesis of Chalcones from Poly Carbonyl Aromatic Compounds Using BF3-Et2O via a Regioselective Condensation Reaction.

A new, simple, highly efficient method for the synthesis of different types of carbonyl chalcones through a regioselective condensation reaction of appropriate 5-acetyl-2-hydroxybenzaldehyde with various substituted acetophenones and 4-hydroxyisothalaldehyde with various substituted aldehydes using BF3-Et2O as a reagent is described.

Bioanalysis of tolvaptan, a novel AVP-V2 receptor antagonist in human plasma by a novel LC-ESI-MS/MS method: a pharmacokinetic application in healthy South Indian male subjects.

A simple, rapid and sensitive liquid chromatography/electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) assay method is proposed for the determination of tolvaptan in human plasma samples using tolvaptan d7 as internal standard (IS). Analyte and the IS were extracted from 100 µL of human plasma via simple liquid-liquid extraction. The chromatographic separation was achieved on a C18 column using a mixture of methanol and 0.1% formic acid buffer (80:20, v/v) as the mobile phase at a flow rate of 1.0 mL/min. The calibration curve obtained was linear (r(2) ≥ 0.99) over the concentration range of 0.05-501 ng/mL. Method validation was performed as per US Food and Drug Administration guidelines and the results met the acceptance criteria. The intra-day and inter-day precision (coefficient of variation) and accuracy results in three validation batches across five concentration levels were well within the acceptance limits. A run time of 2.0 min for each sample made it possible to analyze more samples in a short time, thus increasing the productivity. The proposed method was successfully applied to a pharmacokinetic study of 15 mg and 60 mg tolvaptan tablet formulation in healthy South Indian male subjects under fasting condition.

Liquid chromatography-tandem mass spectrometric assay for the determination of tetrabenazine and its active metabolites in human plasma: a pharmacokinetic study.

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay method has been developed and fully validated for the simultaneous quantification of tetrabenazine and its active metabolites α-dihydrotetrabenazine and ß-dihydrotetrabenazine in human plasma. Tetrabenazine d7 was used as internal standard (IS). The analytes were extracted from 200 µL aliquots of human plasma via solid-phase extraction using C18 solid-phase extraction cartridges. The reconstituted samples were chromatographed on a Zorbax SB C18 column using a 60:40 (v/v) mixture of acetonitrile and 5 mm ammonium acetate as the mobile phase at a flow rate of 0.8 mL/min. The API-4000 LC-MS/MS in multiple reaction-monitoring mode was used for detection. The calibration curves obtained were linear (r(2) ≥ 0.99) over the concentration range of 0.01-5.03 ng/mL for tetrabenazine and 0.50-100 ng/mL for α-dihydrotetrabenazine and ß-dihydrotetrabenazine. Method validation was performed as per Food and Drug Administration guidelines and the results met the acceptance criteria. 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 proposed method was found to be applicable to clinical studies.

Liquid chromatography-tandem mass spectrometric assay for aliskiren, a novel renin inhibitor in micro-volumes of human plasma: a pharmacokinetic application in healthy South Indian male subjects.

This paper describes a simple, rapid and sensitive liquid chromatography/tandem mass spectrometry assay for the determination of aliskiren in human plasma using nevirapine as an internal standard. Analyte and the internal standard were extracted from 100 µL of human plasma via liquid-liquid extraction using tert-butyl methyl ether. The chromatographic separation was achieved on a C18 column using a mixture of acetonitrile and 0.1% formic acid (90:10, v/v) as the mobile phase at a flow rate of 0.9 mL/min. The calibration curve obtained was linear (r(2) ≥ 0.99) over the concentration range of 0.10-1013 ng/mL. Method validation was performed as per US Food and Drug Administration guidelines and the results met the acceptance criteria. A run time of 2.2 min for each sample made it possible to analyze a greater number of samples in a short time, thus increasing the productivity. The proposed method was found to be applicable to clinical studies.

Simultaneous determination of atorvastatin and niacin in human plasma by LC-MS/MS and its application to a human pharmacokinetic study.

A rapid, simple, sensitive and selective LC-MS/MS method has been developed and validated for quantification of the atorvastatin (AT) and niacin (NA) in 250 µL human plasma. The analytical procedure involves a liquid-liquid extraction method using nevirapine as an internal standard (IS). The chromatographic separation was achieved on a Hypurity Advance (4.6 × 50 mm, 5 µm) column using a mobile phase consisting of 0.1% formic acid buffer-acetonitrile (20:80, v/v) at flow rate of 0.8 mL/min. The API-4000 LC-MS/MS was operated in the multiple-reaction monitoring mode using electrospray ionization. The total run time of analysis was 3 min and elution of AT, NA and IS occurred at 1.06, 1.84 and 0.92 min, respectively. A detailed validation of the method was performed as per the US Food and Drug Administration guidelines and the standard curves found to be linear in the range of 0.10-30.0 ng/mL for AT and 20.2-6026 ng/mL for NA, with a coefficient of correlation of ≥ 0.99 for both the compounds. AT and NA were found to be stable in a battery of stability studies, viz. bench-top, autosampler, re-injection, wet-extract and repeated freeze-thaw cycles. The developed assay method was successfully applied to a pharmacokinetic study in humans.

Sensitive and selective liquid chromatography-tandem mass spectrometry method for the determination of metoclopramide in human plasma: application to a bioequivalence study.

A simple, sensitive and rapid method has been developed and validated for determination of the metoclopramide (MCP) in 100 microL human plasma. The analytical procedure involves a liquid-liquid extraction method using tramadol as an internal standard (IS). Chromatographic separation was carried out on a HyPURITY ADVANCE column using a mobile phase consisting of acetonitrile and 10 mm ammonium acetate buffer in the ratio of 80:20 (v/v) at a flow rate of 0.3 mL/min. The total run time of analysis was 2.5 min and elution of MCP and IS occurred at 0.9 and 1.3 min, respectively. A linear response function was established for the range of concentrations 0.53-42.07 ng/mL (r > 0.99). The intra- and inter-day precision values for MCP met the acceptance as per FDA guidelines. MCP was stable in a battery of stability studies viz., bench-top, auto-sampler and freeze-thaw cycles. The developed assay method was successfully applied to an oral bioequivalence study in humans.

Simultaneous determination of niacin and its metabolites--nicotinamide, nicotinuric acid and N-methyl-2-pyridone-5-carboxamide--in human plasma by LC-MS/MS and its application to a human pharmacokinetic study.

An LC-MS/MS method for the simultaneous quantitation of niacin (NA) and its metabolites, i.e. nicotinamide (NAM), nicotinuric acid (NUA) and N-methyl-2-pyridone-5-carboxamide (2-Pyr), in human plasma (1 mL) was developed and validated using nevirapine as an internal standard (IS). Extraction of the NA and its metabolites along with the IS from human plasma was accomplished using a simple liquid-liquid extraction. The chromatographic separation of NA, NAM, NUA, 2-Pyr and IS was achieved on a Hypersil-BDS column (150 x 4.6 mm, 5 microm) column using a mobile phase consisting of 0.1% formic acid : acetonitrile (20:80 v/v) at a flow rate of 1 mL/min. The total run time of analysis was 2 min and elution of NA, NAM, NUA, 2-Pyr and IS occurred at 1.37, 1.46, 1.40, 1.06 and 1.27 min, respectively. A detailed validation of the method was performed as per the FDA guidelines and the standard curves were found to be linear in the range of 100-20000 ng/mL for NA; 10-1600 ng/mL for NUA and NAM and 50-5000 ng/mL for 2-Pyr with mean correlation coefficient of ≥ 0.99 for each analyte. The method was sensitive, specific, precise, accurate and suitable for bioequivalence and pharmacokinetic studies. The developed assay method was successfully applied to a pharmacokinetic study in humans.

Simultaneous determination of telmisartan and amlodipine in human plasma by LC-MS/MS and its application in a human pharmacokinetic study.

A rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay method has been developed and fully validated for the simultaneous quantification of telmisartan and amlodipine in human plasma. Carbamazepine was used as an internal standard. Analytes and the internal standard were extracted from human plasma by solid-phase extraction technique using Waters Oasis® HLB 1 cm3 (30 mg) extraction cartridge. The reconstituted samples were chromatographed on a Hypurity advance C18 column (50 mm×4.6 mm, 5 µm) using a mixture of acetonitrile-5 mM ammonium acetate buffer (pH-4.0) (50:50, v/v) as the mobile phase at a flow rate of 0.8 mL/min. The calibration curve obtained was linear (r≥0.99) over the concentration range of 2.01-400.06 ng/mL for telmisartan and 0.05-10.01 ng/mL for amlodipine. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. A run time of 2.5 min 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.