Development of a positively charged prednicarbate nanoemulsion.

A physically and chemically stable positively charged prednicarbate nanoemulsion was developed as a carrier system for the treatment of atopic dermatitis. Phytosphingosine was used to obtain the positive charge and also because of its supportive properties for the restoration of damaged skin. As production method high pressure homogenization was employed. The optimal concentrations of phytosphingosine, the oil phase, and the emulsifiers were investigated. The production was optimized by investigating the influence of homogenization cycles, homogenization pressure, production temperature and type of homogenizer with respect to particle size, physical stability of the emulsions and chemical stability of prednicarbate. From the results the best formulation and the most appropriate production parameters were identified. In addition it could be shown that during high pressure homogenization the drug is relocated from the inner oil phase of the emulsion towards the stabilizer layer, which could be shown by an increase in chemical stability of prednicarbate. The efficiency of incorporation is influenced by the energy input during homogenization (e.g. number of homogenization cycles) but also by the production temperature. It was found that the nanoemulsions should be produced at elevated temperatures, with low homogenization pressures but higher numbers of homogenization cycles (e.g. 300 bar and 10 cycles). The results prove that the efficiency of high pressure homogenization should not only be judged by investigating the particle size and the physical stability of the emulsions alone, but also by assessing the chemical stability of the incorporated drug.