Abstract

Mahasen A. Radwan*, Iman Y. Zaghloul and Nayira A. Abd Elbaky

An accurate, sensitive and simple high-performance liquid chromatography (HPLC) assay with UV detection has been developed and validated for the simultaneous determination of etoricoxib and its internal standard (IS) flurbiprofen in plasma has been developed. After plasma samples clean up by protein precipitation, followed by solvent evaporation and reconstitution with the mobile phase, an aliquot of the resulted solution were injected into the chromatograph. Peaks were eluted from a Novapak-C8 column using a mobile phase consisting of acetic acid: triethylamine: acetonitrile: water (0.02: 0.01: 41: 59.97, v/v), pH 4.0 at flow rate of 1 ml/min. The detection wavelength was 245 nm with a limit of detection of 50 ng/ml, with a coefficient of variation of 9.8%. Small volumes of plasma were required (200 µL) for etoricoxib determination. The run time was 10 min with etoricoxib and IS eluted in 3.8 and 7.2 min, respectively. The standard curve for the drug was linear in the range of 100 - 5,000 ng/ml for etoricoxib with correlation coefficient > 0.997. This method has been fully validated and shown to be specific, accurate and precise. The assay was selective, where the drug peak was well resolved with no interference from different drugs which could be given concomitantly. The extraction procedure was simple and rapid producing good recovery and a clean baseline, and providing excellent resolution and peak shape for all analytes. The assay was applied to determine the pharmacokinetics of etoricoxib in rats after 15 mg/kg oral dose. Etoricoxib plasma concentrations time profile follows two-compartmental open model with fast distribution and slow elimination phases. This assay is being utilized in determining etoricoxib pharmacokinetics in animals to monitor its interactions with other drugs or food supplements in our laboratory.