Abstract
The distribution of fluocinolone acetonide (FA) in various creams and the release rate of FA from these creams were examined and the results were compared with the observed human vasoconstrictor activity of these creams. The creams were prepared by using various concentrations of surfactants and FA. The distribution of FA in the creams was examined by ultracentrifugation and ultrafiltration methods. The partition coefficients to the oil phase and surfactant phase were also measured. Then, the distribution of FA in the cream was calculated theoretically and these values were compared with the experimental data. From the results for creams containing various concentrations of FA, the distribution of FA in cream is considered to depend simply on a distribution law. As the amount of polysorbate 80 in the cream was increased, the FA release rate and vasoconstrictor activity decreased. The reason was considered to be that FA was trapped in the surfactant phase, and so the free FA concentration in the aqueous phase decreased. In order to enhance the efficacy of the drug, therefore, it is necessary to select correct amounts and kinds of surfactants and to increase the free FA concentration in the aqueous phase.
