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  • Author: Chunzhi Wu x
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Fugen Gu, Jia Ning, Huimin Fan, Chunzhi Wu and Yi Wang

Abstract

Simvastatin is poorly bioavailable because it is practically insoluble in water and shows dissolution rate-limited absorption. Solubilizing effects of several β-cyclodextrin (βCD) derivatives such as HPβCD, SBEβCD and DMβCD on simvastatin in aqueous solution were investigated using the phase solubility technique. The solubility diagram of simvastatin with each βCD derivative could be classified as AL-type, indicating soluble complex formation of 1:1 stoichiometry. Among the above βCD derivatives DMβCD was found to be the ideal complexing agent for improving drug solubility. The simvastatin complex with DMβCD was prepared using the co-evaporation method and was then characterized by differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR) and in vitro dissolution. Dissolution and pharmacokinetic studies indicated that the simvastatin/DMβCD complex exhibited an increased dissolution rate, rapid absorption, and improved bioavailability in rats compared to free drug. Maximum plasma concentration (c max) and the time to reach it (t max) were 21.86 μg mL−1 and 1.4 h for the drug complex, 8.25 μg mL−1 and 3.0 h for free drug, respectively. Main pharmacokinetic parameters such as t max, c max were significantly different (p < 0.01) between the simvastatin complex and free drug. Bioavailability of the simvastatin complex relative to free drug was up to 167.0 %.

Open access

Fugen Gu, Weina Ma, Gendalai Meng, Chunzhi Wu and Yi Wang

Abstract

The aim of this study was to prepare a nasal gel of risperidone and to investigate the pharmacokinetics and relative bioavailability of the drug in rats. Compared with oral dosing, the risperidone nasal gel exhibited very fast absorption and high bioavailability. Maximal plasma concentration (cmax) and the time to reach cmax (tmax) were 15.2 μg mL-1 and 5 min for the nasal gel, 3.6 μg mL-1 and 30 min for the oral drug suspension, respectively. Pharmacokinetic parameters such as tmax′, cmax and AUC of oral and nasal routes were significantly different (p < 0.01). Relative bioavailability of the drug nasal preparation to the oral suspension was up to 1600.0 %. Further, the in vitro effect of the risperidone nasal gel on nasal mucociliary movement was also investigated using a toad palate model. The risperidone nasal formulation showed mild ciliotoxicity, but the adverse effect was temporary and reversible.