| According to the physicochemical properties and absorption characteristic of Helicidum in rats, its 12h sustained-release pellets were developed in this paper.For studying physiochemical properties of Helicidum, the stability of Helicidum solution, absorption of Helicidum in rats' gastrointestinal tract and plasma protein binding rate, high-performance liquid chromatography with UV detection was developed.The studies on solubility showed that the equilibrium solubility in distilled water, HCl (pH1.0) , phosphate buffer( pH7.4), methyl alcohol, methyl cyanide, alcohol were 8.412, 10.554,11.347,6.954,0.840,0.237mg/ml respectively. The chemical stability of Helicidum solution was observed, the result of which indicated that light, temperature and pH had little effect on it.The absorption characteristic was investigated by using the in situ perfusion method in rats' stomachs and intestines. The change of drug amout in circulated solution of tested rats was determined. The absorption rate was 16.03 ± 2.98% in gastic, 4.03 ± 0.93% in duodenum, 6.23 ± 0.98% in jejunum, 6.78 ± 2.63% in ileum.There was no absorption in colon.Nonpareil beads as the core were layered with drug suspension and coated with aqueous dispersions by the bottom-spray fluidized bed. Two kinds of coating materials--Surelease(?) and Eudragit(?) RS/RL were tested in the paper. The optimized formulation of Surelease was 4% quantity of coating material, 15% pores. The optimized formulation of Eudragit was 10% quantity of coating material, RS/RL(17:1), 20% TEC. The sustained-release pellets coated with Surelease was pH independent, but Eudragit was depenedent on pH.Plasma level in healthy beagle dogs after oral administration of conventioned tablets or sustained-release pellets were determined by HPLC method, and their pharmacokinetics parameters were calculated by Kinetica. Compared with conventioned tablets,the relative bioavailability of the pellets coated with Surelease was 101.31%, and the MRT was prolonged significantly.
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