Simultaneous quantitation of rosuvastatin and gemfibrozil in human plasma by high-performance liquid chromatography and its application to a pharmacokinetic study.

A simple, sensitive and specific high-performance liquid chromatography method is described for simultaneous determination of rosuvastatin (RST) and gemfibrozil (GFZ) in human plasma using celecoxib as an internal standard (IS). The assay procedure involved extraction of RST, GFZ and IS from plasma into acetonitrile. Following separation and evaporation of the organic layer the residue was reconstituted in the mobile phase and injected onto an X-Terra C(18) column (4.6 x 150 mm, 5.0 microm). The chromatographic run time was less than 20 min using flow gradient (0.0-1.60 mL/min) with a mobile phase consisting of 0.01 M ammonium acetate:acetonitrile:methanol (50:40:10, v/v/v) and UV detection at 275 nm. Nominal retention times of RST, GFZ and IS were 6.7, 13.9 and 16.4 min, respectively. Absolute recovery of both analytes and IS was greater than 90%. The lower limit of quantification (LLOQ) of RST and GFZ was 0.03 and 0.30 microg/mL, respectively. Linearity was excellent (r(2) = 0.999) in the 0.03-10 microg/mL and 0.3-100 microg/mL ranges for RST and GFZ, respectively. The inter- and intra-day precisions in the measurement of RST quality control (QC) samples 0.03, 0.09, 2.50 and 8.00 microg/mL were in the range 2.37-9.78% relative standard deviation (RSD) and 0.92-10.08% RSD, respectively. Similarly, the inter- and intra-day precisions in the measurement of GFZ quality control (QC) samples 0.30, 0.90, 25.0 and 80.0 microg/mL were in the ranges 2.79-6.27 and 0.96-9.69% RSD, respectively. Accuracies in the measurement of QC samples for RST and GFZ were in the range 85.43-107.23 and 84.98-102.35% respectively, of the nominal values. RST and GFZ were stable in the array of stability studies viz., bench-top, auto-sampler and freeze-thaw cycles. Stability of RST and GFZ was established for 1 month at -80C. The application of the assay in an oral pharmacokinetic study in rats co-administered with RST and GFZ is described.

Determination of rosuvastatin in rat plasma by HPLC: Validation and its application to pharmacokinetic studies.

A specific, accurate, precise and reproducible high-performance liquid chromatography (HPLC) method was developed for the estimation of rosuvastatin (RST), a novel, synthetic and potent HMG-CoA inhibitor in rat plasma. The assay procedure involved simple liquid-liquid extraction of RST and internal standard (IS, ketoprofen) from a small plasma volume directly into acetonitrile. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected onto a Kromasil KR 100-5C18 column (4.6 x 250 mm, 5 microm). Mobile phase consisting of 0.05 m formic acid and acetonitrile (55:45, v/v) was used at a flow rate of 1.0 mL/min for the effective separation of RST and IS. The detection of the analyte peak was achieved by monitoring the eluate using a UV detector set at 240 nm. The ratio of peak area of analyte to IS was used for quantification of plasma samples. Nominal retention times of RST and IS were 8.6 and 12.5 min, respectively. The standard curve for RST was linear (r2 > 0.999) in the concentration range 0.02-10 microg/mL. Absolute recoveries of RST and IS were 85-110 and >100%, respectively, from rat plasma. The lower limit of quantification (LLOQ) of RST was 0.02 microg/mL. The inter- and intra-day precisions in the measurement of quality control (QC) samples, 0.02, 0.06, 1.6 and 8.0 microg/mL, were in the range 7.24-12.43% relative standard deviation (RSD) and 2.28-10.23% RSD, respectively. Accuracy in the measurement of QC samples was in the range 93.05-112.17% of the spiked nominal values. Both analyte and IS were stable in the battery of stability studies, viz. benchtop, autosampler and freeze-thaw cycles. RST was found to be stable for a period of 30 days on storage at -80 degrees C. The application of the assay to determine the pharmacokinetic disposition after a single oral dose to rats is described.

Simultaneous quantitation of etoricoxib, salicylic acid, valdecoxib, ketoprofen, nimesulide and celecoxib in plasma by high-performance liquid chromatography with UV detection.

A specific, accurate, precise and reproducible high performance liquid chromatography (HPLC) method was developed and validated for the simultaneous quantitation of etoricoxib, salicylic acid, valdecoxib, ketoprofen, nimesulide and celecoxib in human plasma. The method employed a simple liquid-liquid extraction of etoricoxib, salicylic acid, valdecoxib, ketoprofen, nimesulide and celecoxib and internal standard (IS, DRF-4367) from human plasma (500 microL) into acetonitirile. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected onto a Kromasil KR 100-5C18 column (4.6 x 250 mm, 5 microm). The chromatographic separation was achieved by gradient elution consisting of 0.05 M formic acid (pH 3)-acetonitrile-methanol-water at a flow rate of 1.0 mL/min. The eluate was monitored using an ultraviolet (UV) detector set at 235 nm. The ratio of peak area of each analyte to IS was used for quantification of plasma samples. Nominal retention times of etoricoxib, salicylic acid, valdecoxib, ketoprofen, nimesulide, IS and celecoxib were 15.63, 17.20, 21.66, 24.95, 26.27, 30.24 and 32.22 min, respectively. The standard curve for etoricoxib, salicylic acid, valdecoxib, ketoprofen and celecoxib was linear (r2 > 0.999) in the concentration range 0.1-50 microg/mL and for nimesulide (r2 > 0.999) in the concentration range 0.5-50 microg/mL. Absolute recovery was >83% from human plasma for all the analytes and IS. The lower limit of quantification (LLOQ) of nimesulide was 0.5 microg/mL and for etoricoxib, salicylic acid, valdecoxib, ketoprofen and celecoxib the LLOQ was 0.1 microg/mL. The inter- and intra-day precisions in the measurement of QC samples, 0.1, 0.3, 15.0 and 40.0 microg/mL (for all analytes except nimesulide), were in the range 2.29-9.37% relative standard deviation (RSD) and 0.69-10.28% RSD, respectively. For nimesulide the inter- and intra-day precisions in the measurement of quality control (QC) samples, 0.5, 1.5, 15.0 and 40.0 microg/mL, were in the range 3.21-7.37% RSD and 0.97-7.06% RSD, respectively. Accuracy in the measurement of QC samples for all analytes was in the range 91.03-106.38% of the nominal values. All analytes including IS were stable in the battery of stability studies, viz. bench top, autosampler and freeze-thaw cycles. Stability of all analytes was established for 21 days at -20 degrees C. The application of the assay in an oral pharmacokinetic study in rats co-administered with celecoxib and valdecoxib is described.