Simultaneous analysis of piperacillin and tazobactam in rabbits: application to pharmacokinetic study.

A simple and rapid assay is developed for the simultaneous analysis of piperacillin and tazobactam in rabbit serum and tissue cage fluid (TCF). To eliminate endogenous interferences, a wavelength switch technique was applied, in which the programmable UV detector changed the monitoring wavelength from 218 to 254 nm at 10 min. After liquid-liquid extraction, sample analyses were performed on a C(18) column by gradient elution; the mobile phase consisted of acetonitrile and phosphate buffer (0.014 m, pH 2.4). Owing to the limited amount of rabbit TCF available, a cross-validation of a proxy matrix was evaluated. The relative standard deviation of the between- and within-batch precision of both compounds was less than 5.1%; the relative error of the between- and within-batch accuracy was less than 7.3%. The recoveries of both compounds in serum and TCF were larger than 80%. This assay was successfully applied to simultaneously analyze piperacillin and tazobactam in rabbit serum and TCF samples.