Determination of valdecoxib in serum using a HPLC-diode array detector and its application in a pharmacokinetic study

A simple, sensitive, isocratic and reproducible reversed phase HPLC method for the determination of valdecoxib, a novel specific COX-2 inhibitor in human serum was developed using a diode array detector and celecoxib as internal standard. The system consisted of a C18 column and a detector set at 240 nm. The mobile phase was a mixture of acetonitrile:water acidified to pH 3.2 with orthophosphoric acid (OPA) (60:40) pumped at room temperature and a flow rate of 1 ml/min. The mean absolute recovery value was about 90%, while the intra (n = 5) and inter (n = 5) assay variations were <18%. The calibration was linear over a concentration range of 20 ng/ml to 200 microg/ml with r2 > 0.999. The limit of detection was < or = 10 ng/ml. The method was used to study the pharmacokinetics of valdecoxib after a single dose oral administration to human volunteers.