Solubility, thermodynamic activity and drug flux out of solid polymer films through membranes

• Applicant: Professor Dr. Geoffrey Lee
• Subject Area: Pharmacy
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 163457744

For release/permeation processes from drug-loaded solid polymer films, the relationship between flux, thermodynamic activity and partition coefficient is studied fundamentally for the first time . In the first 2 years of the project a method was established to determine the saturation solubility of a drug in a thin, solid polymer film and the results published (objective 1 of the application). In the coming 2 years the object 2 of the project will be handled, namely a quantitative determination of the relationship between release/permeation and thermodynamic activity, ie the degree of saturation of the drug in the polymer film. For 3 selected drugs of different lipophilicity drug-laden thin films of different pressure-sensitive adhesives will be prepared. These have different saturation solubility and can therefore for a given value of thermodynamic activity have different drug concentrations. The saturation solubility is adjusted by the addition of anti-dissolving agents to the polymer film. The release/permeation of the drug from these films through excised skin membranes or artificial membranes will be determined. From these results the relationship between flux, thermodynamic activity and concentration will be determined. In addition, our studies of the saturation solubility of drugs in membranes or in a stratum corneum lipid phase will be continued and completed. With all these data we hope to answer the question, whether the maximum measured flux is partially limited by the saturation solubility of the drug in the membrane. The work of first 2 years now makes it possible for us now to contribute to a better theoretical understanding of diffusion processes in multi-layers, consisting of a polymer film and the membrane.

• DFG Programme: Research Grants