Thesis (doctoral)--Ludwig Maximilians-Universität zu München, 1979.

In this study, lanolin alcohol as well as lanolin alcohol-povidone films (1:1 . 5) were investigated as a potential drug delivery system. The in vitro drug release from these films was studied in terms of the effect of agitation, film thickness and drug concentration. The rate of release of Cortisol from lanolin alcohol films was not affected by the intensity of agitation. Moreover, the film matrix was found to remain essentially intact throughout the release process. Further analysis of the data revealed that Higuchi's diffusion-controlled granular matrix model explained the mechanism of Cortisol release from such films. The results of drug release from lanolin alcohol povidone films have shown that although Higuchi's release rate constant was found to be independent of film thickness, it was affected by the intensity of agitation, since the rate constant was found to increase as agitation speed was increased, especially at low speeds. In addition, povidone was found to leach out of the film matrix along with the drug. These factors, in conjunction with further analysis of the drug, explained the failure of this film system to conform to the matrix-controlled diffusion model. The release rate of Cortisol from this film system was found to follow first-order dependence on drug concentration. The drug was found to be completely insoluble in lanolin alcohol, and slightly soluble in povidone. Povidone was found to enhance the solubility of Cortisol in water.

In the present study lanolin alcohol films were investigated as potential drug delivery systems for the controlled release of salicylic acid. A series of experiments were conducted in vitro to study the release of salicylic acid from these films. The effect of changes in film composition and stirrer speed on drug release were examined. Seven film compositions with varying proportions of lanolin alcohol and ethyl cellulose were prepared over the ethyl cellulose concentrations of 0-30% w/w, while keeping the drug concentration at 2.5% w/w. The release data obtained in this study were examined by the Q vs 1/2 relationship and the first-order relationship. This was done to probe deeper into the underlying mechanism of drug release. Upon examination of the release data by the Q vs 1/2 treatment, it was observed that the correlation coefficients were quite high and lag times were only slightly negative in agreement with the observed initial release data. In contrast, the first-order treatment of data showed somewhat lower correlation coefficients and very high negative lag times. These data strongly suggest that the unidirectional release of salicylic acid from the lanolin alcoholethyl cellulose films follows Higuchi's diffusion-controlled granular matrix model. The release rate constant showed an initial increase with inclusion of ethyl cellulose followed by a sharp decline as the ethyl cellulose concentration was further increased reaching a minimum value at about 15-20 percent of ethyl cellulose. Further increases in the concentration of ethyl cellulose increased the rate of drug release with a tendency to level off at about 30 percent ethyl cellulose concentration. The effect of stirring rate on the release rate constant showed that the rates of release of salicylic acid increased with increases in the stirring rate.