Pan Wei-san

Preparation, Evaluation, and NMR Characterization of Vinpocetine Microemulsion for Transdermal Delivery

A novel microemulsion was prepared to increase the solubility and the in vitro transdermal delivery of poorly water‐soluble vinpocetine. The correlation between the transdermal permeation rate and structural characteristics of vinpocetine microemulsion was investigated by pulsed field gradient nuclear magnetic resonance (PFG‐NMR). For the microemulsions, oleic acid was chosen as oil phase, PEG‐8 glyceryl caprylate/caprate (Labrasol®) as surfactant (S), purified diethylene glycol monoethyl ether (Transcutol P®) as cosurfactant (CoS), and the double‐distilled water as water phase. Pseudo‐ternary phase diagrams were constructed to obtain the concentration range of each component for the microemulsion formation. The effects of various oils and different weight ratios of surfactant to cosurfactant (S/CoS) on the solubility and permeation rate of vinpocetine were investigated. Self‐diffusion coefficients were determined by PFG‐NMR in order to investigate the influence of microemulsion composition with the equal drug concentration on their transdermal delivery. Finally, the microemulsion containing 1% vinpocetine was optimized with 4% oleic acid, 20.5% Labrasol, 20.5% Transcutol P, and 55% double‐distilled water (w/w), in which drug solubility was about 3160‐fold higher compared to that in water and the apparent permeation rate across the excised rat skin was 36.4 ± 2.1 µg/cm2/h. The physicochemical properties of the optimized microemulsion were examined for the pH, viscosity, refractive index, conductivity, and particle size distribution. The microemulsion was stable after storing more than 12 months at 25°C. The irritation study showed that the optimized microemulsion was a nonirritant transdermal delivery system.

In vitro and in vivo evaluation of two extended release preparations of combination metformin and glipizide.

A system that can deliver multi-drugs at a prolonged rate is very important to the treatment of various chronic diseases such as diabetes, asthma, and heart disease. Two controlled-release systems, which exhibited similar release profiles of metformin and glipizide, i.e., elementary osmotic pump tablets (EOP) and bilayer hydrophilic matrix tablet (BT), were designed. The effects of pH and hydrodynamic conditions on drug release from two formulations were investigated. It was found that both drug releases from EOP were not sensitive to dissolution media pH and hydrodynamics change, while the release of glipizide from BT was influenced by the stirring rate. Moreover, in vivo evaluation was performed, relative to the equivalent dose of conventional metformin tablet and glipizide tablet, by a three-crossover study in six Beagle dogs. Cumulative percent input in vivo was compared to in vitro release profiles. The linear correlations of metformin and glipizide between fraction absorbed in vivo and fraction dissolved in vitro were established for EOP—a true zero-order release formula, whereas only nonlinear correlations were obtained for BT. In conclusion, drug release from EOP was both independent of in vitro and in vivo conditions, where the best sustained release effect was achieved, whereas the in vitro dissolution test employed for BT needed to be further optimized to be biorelevant.

Study on intralymphatic-targeted hyaluronic acid-modified nanoliposome: influence of formulation factors on the lymphatic targeting.

In this study, hyaluronic acid-modified docetaxel-loaded liposomes were prepared to evaluate the lymphatic targeting after subcutaneous administration, and formulation factors affecting the lymphatic targeting were examined, including free hyaluronic acid, molecular weight, hyaluronic acid-density and particle diameter. The high molecular weight hyaluronic acid-modified docetaxel-loaded liposomes (HA-LPs) and low molecular weight hyaluronic acid-modified docetaxel-loaded liposomes (LMWHA-LPs) were prepared via electrostatic attraction. The physicochemical properties and in vitro drug release were evaluated. The lymphatic drainage and the lymph node uptake were investigated by pharmacokinetics and distribution recovery of docetaxel in lymph nodes, injection site and plasma. The lymphatic targeting ability of optimized Cy7-loaded LMWHA-LPs (LMWHA-LPs/Cy7) was evaluated by near-infrared fluorescence imaging technique. The result showed that HA-LPs and LMWHA-LPs with suitable and stable physicochemical properties could be used for in vivo lymphatic targeting studies. Hyaluronic acid-modified liposome significantly increased the docetaxel recovery in lymph nodes, and displayed higher AUC(0-24h) and longer retention time compared to unmodified liposomes in vivo. In contrast, the presence of free hyaluronic acid hindered the lymphatic drainage and increased the plasma-drug concentration. Importantly, LMWHA-modification improved lymphatic drainage and lymph node uptake of liposomes compared with HA-modification. And Lymph node uptake of LMWHA-LPs depended mainly on LMWHA-density instead of particle size. The results of in vivo imaging showed that LMWHA-LPs/Cy7 significantly located in the lymphatic system. And both DTX-loaded and Cy7-loaded LMWHA-LPs had similar and stable lymphatic target level. Our investigation showed that LMWHA-LPs were a highly promising lymphatic targeting carrier for chemotherapy drugs and diagnostic fluorescence agents.

Novel ophthalmic timolol meleate liposomal-hydrogel and its improved local glaucomatous therapeutic effect in vivo

To overcome the limitations of common eye drops, the study developed a novel timolol mealate (TM) liposomal-hydrogel to enhance drug permeability and prolong residence time in the precorneal region, which achieved more effective local glaucomatous therapeutic effect. Firstly, TM liposome was prepared by an ammonium sulfate gradient-pH regulation method, which its entrapment efficiency reached up to 94% and its averaged particle size is 187 nm with narrow distribution. The corneal permeability through isolated rabbit cornea was measured by modified Franz-type diffusion cells. The results of trans-corneal penetration exhibited that the apparent permeability coefficients (Papp) and the flow rates of steady state (Jss) of TM liposome was 1.50-fold higher than that of the commercialized eye drop, while TM liposome with 0.02% transcutol P was 2.19 times. In order to increase the retention time and improve the stability of liposome, we further developed a TM liposomal-hydrogel formulation by adding 1.0% HPMC K4M in TM liposome. The results showed an stability during a 120 days storage period than TM liposome. Precorneal retention study in vivo indicated that the optimal liposomal-hydrogel formulation had improved bioavailability and its retention time on rabbit corneal surface were significantly longer than that of pure liposomes or eye-drops. No obvious irritations to rabbit eyes were observed by histopathology microscopy after 7 days exposure.. Comparing to the eye drops, the TM liposomal-gel displayed prolonged therapeutic effect in cornea and greatly lowered the intraocular pressure IOP on the eyes of normal and glaucomatous pigmented rabbits.To overcome the limitations of common eye drops, the study developed a novel timolol mealate (TM) liposomal-hydrogel to enhance drug permeability and prolong residence time in the precorneal region, which achieved more effective local glaucomatous therapeutic effect. Firstly, TM liposome was prepared by an ammonium sulfate gradient-pH regulation method, which its entrapment efficiency reached up to 94% and its averaged particle size is 187 nm with narrow distribution. The corneal permeability through isolated rabbit cornea was measured by modified Franz-type diffusion cells. The results of trans-corneal penetration exhibited that the apparent permeability coefficients (P(app)) and the flow rates of steady state (J(ss)) of TM liposome was 1.50-fold higher than that of the commercialized eye drop, while TM liposome with 0.02% transcutol P was 2.19 times. In order to increase the retention time and improve the stability of liposome, we further developed a TM liposomal-hydrogel formulation by adding 1.0% HPMC K4M in TM liposome. The results showed an stability during a 120 days storage period than TM liposome. Precorneal retention study in vivo indicated that the optimal liposomal-hydrogel formulation had improved bioavailability and its retention time on rabbit corneal surface were significantly longer than that of pure liposomes or eye-drops. No obvious irritations to rabbit eyes were observed by histopathology microscopy after 7 days exposure.. Comparing to the eye drops, the TM liposomal-gel displayed prolonged therapeutic effect in cornea and greatly lowered the intraocular pressure IOP on the eyes of normal and glaucomatous pigmented rabbits.