[Contributions to the liberation of drugs from suspension ointments. Part 13: The effects of physiochemical factors on the liberation of prednisolone from oleogels (author's transl)].
The liberation rates of oleogels containing 0.25% of prednisolone can be stated by the following equation: q=f(square root of t). The regression equations may be used to calculate the liberation rate constants from which the apparent diffusion coefficients are obtainable. These and other data (lag time, distribution coefficient, saturation solubility, water absorption, consistency) are discussed in regard to possible correlations. For an ordered series of Onicetan-castor oil oleogels, there exists a relationship between liberation rate, the solubility and the distribution coefficient that can be expressed mathematically. The diffusion rate of the drug in the oleogels varies with the lipid or lipid mixture used, it exceeds largely the diffusion rate in the horny layer and, consequently, it is of particular importance to the transfollicular route of the cutaneous drug absorption. No convincing correlation could be established between the consistency (as determined by penetrometry) and the releasing quality. The binding strength of the lipid fixed at the Aerosil structure depends on its hydrogen-binding capacity and becomes demonstrable, for example, by studying the water-absorbing capacity.