Abstract:Objective To study the accumulative release of nor cantharidin chitosan nano particles(NCTD-(:S-NP) in vitro，investigate its properties and absorption characters in rat intestine in vivo and invitro，and evaluate the correlation among the release in vitro，the absorption in rat intestine in vivo and invitro. Methods NCTD-CS-NP was prepared by ionic cross-linkage process, dynamic dialysis was used to study the release dynamics of NCTD-CS-NP in vitro. The intestine in rats was cannulated for in vivo recir-culation and evened gut sac in vitro. The absorption character and regularity were studied at various intes-tine segments and at different concentration. Results The absorption rate constants (K,)of NCTD and NCTD-CS-NP in various segments were duodenum>jejunum>ileum>colon. At the duodenum, the K, of NCTD and NCTD-CS-NP were 15. 69 and 29. 16 h-1，respectively. The concentration had no distinc-tive effect on the absorption kinetics (P>0. 05). The absorption of NCTD was a first-order process with passive diffusion mechanism. The absorption law in vivo was the same as in vitro，the correlation coeffi-cient between them was 0. 999 4. Conclusion NCTD-CS-NP could improve the absorption of NCTD in ratsmall intestine. NCTD is well absorbed at the superior and middle segments of intestine. The concentra-tion of NCTD has no distinctive effect on the absorption kinetics. The release of drug in vitro and its up-take is well correlated.