The hydrated filtration membrane renders possible uniform hydration of hydroxypropylmethylcellulose hydrogel with subsequent uniform release of dissolved scopolamine bromide. Exponential dependence of the diffusion coefficient on the graded medium dimension of the pores of the testing membrane makes possible the estimation of the reactive fractal dimension DR by means of the modified exponent (3 – DR).With increasing concentration of scopolamine bromide in xerogel (14.7 to 77.8 mg/cm3), DR decreases within a range of 2.814 to 2.704. A comparison with the structure of a suitable fractal (Menger sponge) leads to a conclusion about suitability of the use of membranes for the testing of concentrations of scopolamine bromide in xerogel, if DR > 2.727.

        Key words: scopolaminium bromide – hydrogel – filtering membrane – diffusion coefficient – reactive fractal dimension