Study On Floating Sustained Release Tablets Of Ligustrazine Phophate

Floating drug delivery system (FDDS) is one of the approaches to increase the retention time of an oral dosage form in the stomach. FDDS have a bulk density lower than gastric fluids and thus remain buoyancy in the stomach without affecting the gastric emptying rate for a prolonged period of time. In the present study, the floating and swelling characteristic of several excipients used in controlled release technology were examined. The floating behavior was evaluated with resultant weight measurements, and it is carried out under the guidance of the law of Archimede, while a gravimetric method was employed for studying their swelling. The result indicated that buoyancy generation and duration is controlled by water uptake (W) and swelling (V) of the floating tablet. The study on the relationship of W and V demonstrated that in all cases, the slopes of W(SW) versus the square root of time were lower than those of V(SV). The result indicates that V expansion can generate a buoyancy force substantial enough to counteract W increases. Furthermore SW/SV was calculated. This ratio seems to correlate with the floating behavior of the excipients.A bi layer floating tablet for gastric retention was made by using Ligustrazine Phophate(TMPP) as a model drug, which is a effervescent FDDS .The HPMC was the main matrices while Eudragit RS was a polymer hydration-modulate matrices. The factors affecting buoyancy were investigated. In order to find the optimum floating layer formulas, Uniform design was carried out. On the basis of pre-experiments, the factors that affect drug releasewere found out. On the basis of orthogonal experiments, the drug-layer formulas were optimized. Dosage forms with the optimum formulation showed ideal buoyancy and drug release characteristics. Then, the release mechanism was studied and it was indicated that the drug release was affected by such factors as diffusion, erosion, relaxation, etc.A noneffervescent FDDS is made by using compritol 888 as floating aid and sustained matrices. In the research of process, an optimum process is found. The bi layer floating sustained tablet which is effervescent and one-layer floating sustained tablet which is noneffervescent are compared, the results demonstrated that the former is superior to the latter.r- Scintigraphy was used for the study of stomach retention of 99mTc-MIBI labled floating tablet. As the results have shown, the floating sustained release tablet floated on the gastric content and stayed within stomach for Shours.The in vivo pharmacokinetics of the floating sustained release tablets in dogs was carried out by HPLC. Its Tmax(4.0h ), t1/2(4.857h), were bigger than commercial tablet, while Cmax(263) is lower than commercial tablet. The relative bioavailability was 119.7%. Obvious correlation existed between absorption percentage in vivo and release rate percentage in vitro.