First-order release kinetics is characterized by a linear dependence of the release rate on the released amount of the active ingredient, the triple of the absolute value of the exponent of the exponential function expressing the reactive fractal dimension DR. Scopolamine bromide release from hydroxypropylmethylcellulose hydrogel was first expressed by first-order kinetics with an estimated DR ranging from 2.98-3.00. The employment of an exponential equation with the exponent of release n renders it possible to make an assumption about the mechanism of release. Within a range of n = 0.505-0.550, estimated DR = 2.46-2.94. In this region, release by means of the mechanism of Fick's diffusion prevails. DR = (3/n)-3 generally holds true for the relationship between both variables, which makes it possible to use the knowledge gained in the experimental influencing of the exponent of release in the examination of the relationship between the reactive fractal dimension and the mechanism of release of scopolamine bromide from hydrogel. An increase in the exponent of release markedly decreases the corresponding values of reactive fractal dimension.

Katedra farmaceutické technologie Farmaceutické fakulty Univerzity Karlovy Hradec Králové