High-performance liquid chromatographic assay for the simultaneous determination of ethyl clofibrate and clofibric acid in plasma. Evaluation of plasma stability of ethyl clofibrate polylactic nanocapsules in human and rat plasmas.

A rapid, sensitive, and selective HPLC assay was developed for the simultaneous determination of ethyl clofibrate and its major metabolite, clofibric acid, in plasma of humans and rats. The assay involves extraction of the compounds into chloroform-isoamyl alcohol (99:1, v/v) from plasma acidified with sulfuric acid. For human plasma, the overall recoveries of ethyl clofibrate and clofibric acid were 63 and 90%, respectively. The limits of detection of the assay for ethyl clofibrate and clofibric acid in human plasma were 1.1 and 1.5 micrograms/ml, respectively. Limits of quantitation of the assay for ethyl clofibrate and clofibric acid in human plasma were 3.6 and 4.9 micrograms/ml, respectively. The HPLC assay was used to monitor the plasma concentration-time profiles of ethyl clofibrate released from polylactic nanocapsules both in man and rat. The simultaneous determination of ethyl clofibrate and clofibric acid provided evidence that these colloidal systems are stable in human plasma whereas they are lysed in rat plasma.