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Biomedical subjects

V R Shah

Publications and source records attributed to V R Shah.

23 records · Page 2Linked to original sources
PubMedDate not supplied

High-performance liquid chromatographic-ultraviolet assay for the simultaneous quantitation of BMS-181101 and its putative hydroxy metabolites in rat and monkey plasma.

A specific, accurate, precise, and reproducible High-performance liquid chromatographic-Ultraviolet (HPLC-UV) method was developed for the simultaneous quantitation of BMS-181101 (I), a new antidepressant, and its putative metabolites, 6'-hydroxy (II) and 7'-hydroxy (III) of BMS-181101 in rat and monkey plasma. The assay procedure involved solid-phase extraction of the three analytes and the internal standard (IS; BMY-42568) on 1 mL Bond Elut CN cartridge using an automated solid phase extraction controller (ASPEC) system. The final elution of the analytes was performed using 0.25% triethylamine in methanol. The eluate mixture was evaporated to dryness, the residue was reconstituted in the mobile phase and injected onto a Zorbax Phenyl column (4.6 x 250 mm; 5 microns) at a flow-rate of 1.2 mL/min. The mobile phase consisted of 20% acetonitrile, 10% methanol, 69% water and 1% 1.0 M ammonium phosphate and 1.0 M tetramethylammonium hydroxide mixture adjusted to pH 3 by phosphoric acid. An ultraviolet absorbance detector set at 287 nm was used to detect the analytes. The nominal retention times were 5, 8, 15, and 18 min for II, III, I, and IS, respectively. The standard curves for the three analytes were linear in the concentration range of 50-1000 ng/mL. The lower limit of quantitation was 50 ng/mL for each analyte. The analyses of quality control (QC) samples indicated that the nominal values could be predicted with an accuracy of (+/-) 10.5% for all three analytes in rat and monkey plasma. The precision values of the QC samples for all three analytes were within 12.7% RSD for rat and monkey plasma. All three analytes and the IS were stable in the autosampler for at least 38 h; freeze/thaw stability of the 3 analytes was established for three cycles. Stability of BMS-181101 was established for one month at -20 degrees C. The application of the assay to a pharmacokinetic study in monkey is described.

Animals↗
PubMedDate not supplied

High-performance liquid chromatographic assay for the quantitation of nadolol in human plasma using fluorescence detection.

A rapid and sensitive HPLC-fluorescence assay was developed and validated for the determination of nadolol, a beta-blocker, in human plasma. Nadolol and the internal standard (desmethyl nadolol) were extracted from alkalinized plasma into methyl-tert.-butyl ether. The organic solvent was evaporated under nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected on to a C18 silica column (25 cm x 4.6 mm i.d.) at a flow rate of 1.4 mL/min. The mobile phase was 0.05 M monobasic ammonium phosphate (pH 4.2) and acetonitrile (84: 16, v/v). Fluorimetric detection was performed at excitation 230 nm and emission 330 nm. The nominal retention times were 3.3 and 4.3 min for the internal standard and nadolol, respectively. The lower limit of quantitation was 5 ng/mL and linearity (R2 > or = 0.994) of the standard curve was demonstrated between 5 and 500 ng/mL. The analysis of quality control (QC) samples at 60, 200 and 400 ng/mL resulted in precision estimates < or = 7.0% relative standard deviation (RSD) for the inter-assay and < or = 6.3% RSD for intra-assay. The predicted concentrations of the QC samples deviated < 10% from the nominal values. The extraction recovery of nadolol from human plasma was 64%. Nadolol was stable in human plasma at -20 degrees C for at least 5 months and for at least three freeze-thaw cycles. Nadolol and the internal standard were stable in the autosampler at 5 degrees C for at least 40 h. Overall, the assay was accurate, precise, sensitive, specific, and reproducible for the analysis of nadolol in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Stereoselective analysis of nadolol in human plasma.

A stereoselective method, involving a single liquid-liquid extraction step, was developed and validated for the analysis of nadolol in human plasma. The assay involved extraction of nadolol and desmethyl-nadolol (as internal standard (IS)) from alkalinized plasma into dichloromethane. The organic solvent was separated and evaporated under nitrogen at 40 degrees C. A chiral derivatization scheme with (R)-(-)-napthylethylisocyanate (50 microL of 0.1% solution in dichloromethane for 60 min) was employed to convert the enantiomers of nadolol into the corresponding diastereomeric derivatives. The residue was reconstituted in the mobile phase and injected onto a C-18 column. The mobile phase was a mixture of methanol:tetrahydrofuran:water (52:7:41 by vol) containing about 0.001% v/v of both phosphoric acid and tetramethylethylenediamine. Fluorimetric detection was performed at excitation 230 and emission 330 nm. The assay was specific for the enantiomers of nadolol and the lower limit of quantitation was 2 ng/mL for each of the enantiomers. Analysis of quality control samples resulted in precision estimates of 7% RSD for inter-assay and 10.1% RSD for intra-assay and the predicted concentrations deviated less than 9.4% of the nominal values for the four enantiomers. The extraction recoveries of the individual enantiomer was about 70%. Stability of nadolol enantiomers were established for four freeze/thaw cycle periods and in the autosampler at 5 degrees C for at least 116 h.

Adrenergic beta-Antagonists↗