Plasma was separated by centrifugation for 2 min at 10000 g and kept at -20 until analyzed. Written informed consent was obtained before administering the tablet. Plasma was harvested and kept at -20 until analyzed. The non-compartmental model contained in the program was used. The run time of the assay, therefore, was set at 30 min.
Lines join experimental data points.
Direct exposure of rofecoxib solution to the laboratory light resulted in degradation of the drug and appearance of a major HPLC peak 3 min before the drug. Rofecoxib crystals extracted from tablets maintained their potency at least for a 4 months period of storage in a container rapped in aluminum foil and kept refrigerated. We cannot offer a reasonable explanation for the observed variability due to the limited sample size used. The authors reported the half-life of 6.7 and 2.6 h in rats and dogs, respectively. The HPLC assay presented here is suitable for determination of rofecoxib in the rat and human plasma following therapeutic doses.