Abstract: AimTo investigate the stereoselective pharmacokinetic process of tetrahydropalmatine (THP) in rats. MethodsThe concentrations of tetrahydropalmatine enantiomers in rat plasma were determined by coupled achiral and chiral HPLC method. The differences in plasma concentrations and pharmacokinetic parameters between the two enantiomers were compared by paired t-test. ResultsThe plasma levels of l-THP were always higher than those of d-THP in eight rats. There was significant difference between the main pharmacokinetic parameters of the two enantiomers. Conclusion Tetrahydropalmatine showed significant stereoselective pharmacokinetics in rats after an ig dose of the racemate.