| Using 2,3,5,6-tetramethylpyrazine phosphate （TMPP） as a model drug, intranasal drug delivery system was studied systemically in the present work, including pre-formulation, absorption enhancer screening, preparation and characterization of TMPP-chitosan microspheres, Pharmacokinetics, brain targeting ability assess and TMPP solution stability test.Firstly, a sensitive and precise HPLC method for TMPP determination was established, and then the stability and the equilibrium solubility of TMPP were studied.. In the stability study, effects of solution pH, ionic strength and general acid-base catalysis were investigated. TMPP was found to be stable under the specified conditions. The solubility of TMPP increased with pH decrease. 7% nicotinamide was selected to reach the solubility desired.Subsequently, an in situ nasal perfusion technique in rats was utilized to screen absorption enhancers. The in vitro absorption rate constants （ka） were 0.158, 0.233, 0.169 mg·min-1 for the control group, 0.5%HP-β-CD and 0.5%Tween80 group, respectively. A considerable difference was found between the control group and the 0.5% HP-β-CD or 0.5%Tween80 group （P<0.05）. However, no statistical difference was found between the control group and other groups （P>0.05）. All the enhancers investigated could enhance the intranasal absorption of TMPP significantly. Taking safety reason into account, 0.5% HP-β-CD, 2% Tween80, 0.5% CS （50）, 0.5% TMC （50）, 0.5% CS （100） were selected for further studies.In chapter 3, chitosan microspheres were prepared using pH adjusting technique. Influence of formulation factors and the process factors on the properties of microspheres were studied. Then orthogonal design was used to select the optimal formulation based on the average diameter, the drug loading and the entrapment efficiency of TMPP. Chitosan microspheres made from the optimal formula have good sphericity and narrow size distribution. The average diameter was （50.2±0.7）μm. The drug loading was （39.94±0.21）%. The entrapment efficiency was （73.9±0.24）%. Effects of chitosan molecular weight and particle size on the swelling and release behavior of the microspheres were investigated. The release mechanism of TMPP from the microspheres was found to be a combination of diffusion and erosion.. The evaluation indexes showed that the optimal formula and process had fine reproducity and stability.In chapter 4, Pharmacokinetics of TMPP was studied after intranasal administration of different TMPP solutions and different types of TMPP chitosan microspheres. The Pharmacokinetics parameters were calculated by 3p97 software. The in vivo plasma concentration-time profiles of the TMPP solutions and TMPP chitosan microspheres. can be described with a two-compartment model.The absolute bioavailability of 2%Tween80 group and TMPP chitosan microsphere （100kDa, 50μm） were 78.4% and 86.8%, respectively, with significant differences between the two groups （P<0.05）. A good correlation was found between the in situ absorption data and plasma concentration in vivoBy using brain homogenate method, the distribution of TMPP in brain tissue after intranasal administration of TMPP solution was investigated in chapter 5.The ratios of AUC brain/AUCplasma were calculated and compared. It was noted that the ratio increased by 4.9 times after intranasal administration of TMPP solution compared to that of intraveneous injection, indicating the brain targeting effect of intranasal administration route..Tween80 could enhance the intranasal absorption of TMPP significantly, however, couldn’t affect its distribution in brain.In the stability test, the drug appearance, pH and content of TMPP solution were found to be stable at 40℃and room temperature for three months.
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