Studies On Sustained-release Yixintong Hydrophilic Gel Matrix Tablets

Yixintong was a kind of Flavonoids, extracted from Hawthorn Leaves. Yixintong has the efficacy of dispersing blood stasis, promoting heart blood circulation, and accommodating vein fettle, etc. It was used in the treatment of coronary heart disease, angina, high blood lipid, cerebral artery ischemic. As a kind of medicine of used for heart and cerebral blood vessel disease, it was needed to be eaten frequently for a long time.The in situ small intestinal circulation method was applied to study the absorption effect of vitexin-2"-o-rhamnoside and other primary components in Yixintong. The results showed that the absorption of Yixintong was very low.In order to increase the oral absorption of Yixintong, hydrophilic gel matrix sustained-release tablets of Yixintong was developed using various hydrophilic gel materials. Prolonged stagnancy of Yixintong in the stomach and small intestine was obtained in virtue of the adhesive effect of hydrophilic gel. In this way, the gradually released Yixintong might pass through the alimentary canal with a low speed, then got to the position where it would be absorbed effectively because of the increased contacted areas and time between Yixintong and mucous membranes. So that Yixintong would have enough time to be dissolved and absorbed efficiently, increased bioavailability and reduced administration frequency of Yixintong would be obtained.The tablets’ prescription was optimized and in vitro releasing characteristics of the tablets were investigated. An appropriate formulation for Yixintong sustained release tablet was obtained, that was Yixintong (60%), xanthan gum (20%), pregeletinized starch (18%), stearic acid (1%), and talc (1%). Yixintong was completely released from the tablets within10hours in distilled water by zero order, and also in a well controlled profile in pH6.8buffer solution.Xanthan gum has a good conglutinative character and holds strong viscosity especially. So a relatively large amount of drug could be composed in a relatively small sized tablet. The technique of powder directly tabletting is very convenient. At the same time the release behavior of Yixintong from the hydrophilic gel matrix sustained-release tablets, from the tablets composed of xanthan and locust bean gum, and from the tablets composed of Carbopol were also investigated.Methods used in detecting the content of total flavonoids, in investigating of the in-vitro releasing behavior (spectrophotography) and in absorption study in small intestine (HPLC) showed that all methods had good linearity, recovery and accuracy.