Abstract: AIM: To study the pharmacokinetics and bioavailability of catalpol in rats.METHODS: LC-MS/MS method was established for the quantitation of catalpol.The plasma concentration of catalpol after i.g. administration of 50, 100 and 200 mg/kg dose of catalpol to six rats was calculated by peak area ratio of the determinated (catalpol) and the internal standard (aucubin) obtained by Xcalibur 1.4 program. The main pharmacokinetic parameters were obtained by DAS 2.0 program. The figures were checked by t text method, and calculated for bioavailability.RESULTS: The plasma concentration-time curve of catalpol conformed to two compartment model.After i.g. administration of 50, 100 and 200 mg/kg dose of catalpol, AUC_0→∞ values increased in proportion to dose. t_1/2 appeared to be independent of dose. Mean AUC_0→∞ was (70±23) and (104±11) μg·h·mL^-1 respectively after i.g. and i.v. administration of 50 mg/kg dose,the extent of bioavailability of catalpol was 66.7%.CONCLUSION: The results of the pharmacokinetic study of catalpol showed that it exhibited first order kinetic characteristics and the bioavailability was satisfied.

Key words: Catalpol , LC-MS/MS, Pharmacokinetics , Bioavailability