The Study On Thymopentin Microemulsion

The demands on the performance of pharmaceutical preparation in recent years are mainly focus on better stability, higher bioavailability, fewer side effects, controlled release and target directed drug delivery systems. In respect to the liquid formulations,surfactants play a key role in the development of many novel drug delivery systems including liposomes and cyclodextrins encapsulation. Microemulsions are also being extensively investigated along with those liquid drug delivery systems.A systematic evaluation of Thymopentin (TP5) microemulsion was carried out in this study. The selection of surfactant emulsifier,cosurfactant,oil and water was based on the pseudo-termary phase diagrams constructed using electrical stirring technique. The preparation was found to be a water in oil type microemulsion with ODO-L(an emollient used for chewing gums)as emulsifier, ethanol as cosurfactant, caprylic triglyceride as oil phase, and distilled water as water phase. Physicochemical properties including conductance,viscosity,light refractive index and pH value and visual appearance under various temperature and shelf life were studied for the microemulsion prepared. The concentration change of TP5 during the prepartion process was evaluated by an UV method,the result found no change in TP5 under the conditions of pH 2.5 to 7.0 for 24 hours, or stirring at 800r/min under 60℃for 1.5 hours. The TP5 concentration study also indicated that the microemulsion prepared was stable after storage at 25℃or 40℃for one month, while TP5 solution can not be stored more than 4 days at 4℃.The in vivo elevation of total white blood cell (WBC) and CD3+ cell count in gamma-ray irradiated immuno-compromised kunming mouse was used to evaluate the pharmacologic efficacy of TP5 microemulsion. The results showed that the increment of WBC and CD3+ cells in mice with gavage of TP5 microemulsion was close to the increment in mice receiving venous injection of TP5 solution, while gavage of TP5 solution showed no such increment. Therefore the microemulsion of TP5 prepared was a bioactive formulation.Although the mechanisms of absorption and biofunction of TP5 microemulsion are still obscured, the results from this study further support the feasibility of using microemusion as delivering vehicle for peptide drugs.