Abstract: AimTo investigate the in vitro recovery and influencing factors of ketoprofen in microdialysis probe, and study the pharmacokinetic of unbound ketoprofen in rat after iv administration. MethodsThe recovery of ketoprofen was detected by a concentration difference method. After microdialysis probe was inserted into the jugular vein of male Wistar rats, the probe was infused with various concentrations perfusate. The in vivo recovery and the pharmacokinetics of unbound ketoprofen in rat were investigated. Dialysate samples were determined by HPLC. ResultsThe recovery detected by gain was as the same as that by loss; the recovery was independent of the drug concentration surrounding the probe. The in vitro recovery was 28.75% by concentration difference method and the in vivo recovery was (40.3±2.7)% by retrodialysis method. After iv administration of ketoprofen in rat, T_1/2, AUC and CL of unbound ketoprofen were (181±16) min, (112±27) μg·min·mL^-1 and (0.22±0.05) L·min^-1, respectively. ConclusionMicrodialysis sampling can be used for the pharmacokinetic study of unbound ketoprofen in rat.