Abstract: Objective To investigate physicochemical properties and the absorption kinetics of norcantharidin(NCTD) at different intestine segments in rats. Methods The dissolubility and n-octyl alcohol/water partition coefficient were determined. The intestine in rats was cannudated for in situ recirculation, UV and HPLC were respectively used to determine the concentrations of UV spectrums of phenol red and NCTD. The absorption of NCTD was studied at different intestine segments, and with different concentration of NCTD. Results The absorption rate constants (Ka) at duodenum, jejunum, ileum, and colon were 0.1623, 0.1260, 0.0084, 0.0035h ^-1 respectively. Ka from intestine at NCTD concentration of 70, 80, 90μg·mL^-1 were 0.0112, 0.0056, 0.0071h^-1 respectively. Conclusion The concentration of NCTD had no distinctive effect on the absorption kinetics. The absorption of NCTD was a first -order process with passive diffusion mechanism, which indicated that NCTD could be prepared as sustained -release dosage form for administration once a day.

Key words: norcantharidin, physicochemical properties, absorption kinetics, intestinal recirculating method in situ