SENSITIVE HPLC ASSAY FOR KETOPROFEN IN HUMAN PLASMA AND ITS APPLICATION TO PHARMACOKINETIC STUDY

A selective and sensitive HPLC method was developed for the analysis of ketoprofen in human plasma. The assay involves an extraction of the drug and the internal standard (piroxicam) into diethyl ether from acidified plasma and then back-extracted into a small volume of alkaline aqueous solution before injection onto the HPLC column. A microbore column (2 mm I.D. x 10 cm) packed with a C18 reversed-phase material (5-mu-m ODS Hypersil) was used. The chromatographic separation was accomplished with a mobile phase comprising a mixture of acetonitrile-methanol-water (15:20:65, v/v) containing 10 mM Na2HPO4 buffer, pH 4. The mobile phase was pumped at a flow rate of 0.5 ml/min. The eluant was monitored at 258 nm. With this procedure coefficients of variation were less than 10%. The detection limit was 0.05-mu-g/ml (i.e., 50 ng/ml) of plasma. The highly sensitive nature of this method was applied successfully to the determination of ketoprofen in human plasma for pharmacokinetic studies.