A simple, rapid and selective method was developed. The method was validated and found to be linear in the range of 100-4000 ng/ml. Chromatographic peaks were separated by means of a 5 μm, C18 silica column using acetonitrile and phosphate buffer (0.05 M) in proportion of 40:60 (pH 4.0) as a mobile phase. The retention time of torsemide was 5.00±0.20 min. The chromatograms showed good resolution and no interference from plasma. The mean recovery from human plasma was found to be above 82%. Both inter-day and intra-day accuracy and precision data showed good reproducibility. This method was applied to a single dose bioequivalence study. Log transformed values were compared by ANOVA followed by classical 90% confidence interval. Confidence limits for Cmax, AUC0-t and AUC0-inf ranged from 98.6 to 102.8, 101.8 to 105.3 and 102.4 to 105.5 respectively. These results suggested that the analytical method was linear, precise and accurate. Test and reference product were found to be bioequivalent.

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& A simple, rapid, and sensitive HPLC with UV detection was developed and validated for the determination of dexibuprofen in human plasma. The method involves extracting dexibuprofen with acetonitrile. Chromatographic separation was carried out on a C18 column using mixture of acetonitrile:methanol:potassium dihydrogen phosphate as mobile phase with UV detection at 222 nm. The retention time of dexibuprofen was 4.720 AE 0.3 min. The method was validated for selectivity, linearity, and range; intra-day and inter-day accuracy; and precision and stability. The developed and validated method was applied to a single oral dose of 400 mg dexibuprofen reference formulations (IBUSOFT 400 tablets manufactured by Emcure Pharmaceuticals Ltd, Pune, India) or test formulations (Medley Pharmaceuticals Ltd, Mumbai, India) that were administered to Indian healthy human male subjects. Serial blood samples were collected for 12 hr after administration of formulations. Pharmacokinetic parameters were determined for both the formulations. C max , AUC 0-t and AUC 0-inf , were evaluated for bioequivalence after log-transformation of data using ANOVA with a 90% confidence interval level. All of the tested parameters were within the acceptable range of 80-125%. The present method is simple and readily applicable to pharmacokinetic and routine bioequivalence studies of these compounds with an acceptable sensitivity.

Epalrestat is a new drug for diabetic neuropathy. A new, simple, rapid very sensitive, and accurate high performance thin-layer chromatographic (HPTLC) method has been developed and validated for estimation of epalrestat in plasma. HPTLC was performed on silica gel 60F 254 plates with ethyl acetate-toluene-acetic acid, 60 + 40 + 2 (v/v), as mobile phase. Nitrofurantoin was used as internal standard. Densitometric scanning was performed in absorbance mode at λ λ = 390 nm. The R F values of the internal standard and drug were 0.4 and 0.6, respectively. The response was a linear function of concentration over the range 0.1-6.0 μg mL -1 (r 2 = 0.9974). Mean extraction recovery was >63%. Intra-day and inter-day precision (% CV) of the assay were in the range 1.62-4.68% and accuracy was >95%. This method can be applied to pharmacokinetic and bioequivalence studies. Preparation of Calibration Standard Solutions in PlasmaCalibration standards were prepared by spiking drug-free plasma with epalrestat working standard solution (100 μg mL -1 , 60 μL) to furnish a 6 μg mL -1 calibration standard. This solution was further diluted with drug-free plasma to furnish calibration

A simple, rapid, selective and sensitive reversed phase HPLC method was developed and validated for the determination of rebamipide from plasma. The drug was extracted with a mixture of chloroform and isopropyl alcohol. Rebamipide was measured in plasma using a validated HPLC method with UV detection at 280 nm. Chromatographic peaks were separated on a 5 µm C-18 silica column using a mixture of acetonitrile, water, methanol and acetic acid as a mobile phase. The chromatograms showed good resolution and no interference from plasma.The retention time of rebamipide and internal standard were approximately 4.9± ± ± ± ±0.3 min and 7.6± ± ± ± ±0.3 min, respectively. The mean recovery from human plasma was found to be above 91%. The method was linear over the concentration range of 10 to 500 ng/ml with coefficient of correlation (r 2) 0.991. Both intra-day and inter-day accuracy and precision data showed good reproducibility. This method can be successfully applied to pharmacokinetic studies.