EFFECT OF FRACTAL DIMENSION ON DRUG PERMEATION THROUGH POROUS ETHYLCELLULOSE FILMS

Fractal geometry was applied to quantify the complexity of an internal structure of a porous film prepared with ethylcellulose (EC) and diet hylphthalate (DEP) as a plasticizer. EC was dissolved together with DE P in a water-ethanol mixture solution, and then evaporated on Teflon p etri dishes in order to make porous EC films. Boundary lines of the po rous structures in the EC film cross section were taken by a confocal laser microscope as image data, and these images were fed into a compu ter to estimate the fractal dimension. The porous structure in EC film was observed to be a typical fractal and its complexity was quantifie d as a non-integral fractal dimension. No clear correlation was observ ed between the fractal dimension and the porosity of EC films, suggest ing that they were mutually independent parameters representing the po rous structure in the EC films. The permeation of theophylline through the EC films was determined by using two-chamber diffusion cells. A f airly good relationship between the permeability coefficient of theoph ylline and the fractal dimension was observed, suggesting the usefulne ss of the fractal dimension as a novel parameter for evaluating drug p ermeation through porous films. (C) 1998 Elsevier Science B.V.