OBJECTIVE To investigate the absorption kinetics and stereoselectivity of tetrahydropalmatine(THP) enantiomers in rat intestine.METHODS The in situ intestine recirculation and the intestinal loop experiments were performed in rats.The concentrations of phenolsulfonphthalen and THP were determined by validated UV-HPLC assay,respectively.The d-/l-THP enantiomers ratios in recirculation solutions and plasma samples from portal vein were obtained by chiral separation.RESULTS The absorption rate constants(Ka) at THP concentrations of 10,25 and 50 mg·L-1 were 0.403,0.461 and 0.402 h-1,respectively.Ka at pH of 4.5,6.5 and 8.0 were 0.353,0.458 and 0.409 h-1 ,respectively.The d-/l- ratios in recirculation solutions and plasma samples from portal vein remained as closely as 0.5∶0.5.CONCLUSION The concentrations of THP and pH of drug solution had no significant effect on the absorption kinetics.The absorption of THP from intestine is mainly via passive transport mechanism and no stereoselectivity is displayed in the absorption of the enantiomers.
HONG Zhn-ying;FN Guo-rong;CHI Yi-feng;WEN Jun;YIN Xue-ping;WU Yu-tin.
Studies on Intestinal Absorption Characteristics of Tetrahydropalmatine in Rats [J]. Chinese Pharmaceutical Journal, 2007, 42(14): 1104-1107
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