A new method for characterizing the release of drugs from single agglomerates

The aim of this thesis was to identify some functionality related characteristics of pharmaceutically relevant solid materials and to study the effect of their variation on processing behaviour and product performance. For this purpose, particles with different characteristics were prepared under a variety of conditions by crystal agglomeration, wet granulation and spray drying. The effect of particle size distribution on the evolution of the tablet microstructure during and after compression was investigated. The compression behaviour of particles with different nominal strength and degrees of agglomeration was studied and the influence of the surfactant concentration of amorphous particles on the compression behaviour was examined. The response of the powders to compression was described with the help of various techniques characterising the microstructure and tensile strength of the tablets produced. Furthermore, a method suitable for observing drug release from single matrix granules was developed and used to study the effect of granule porosity and compaction pressure on the drug release process. The particle size distribution did not influence the evolution of the tablet porosity or the tensile strength during compression, but it could have an effect on the evolution of the tablet microstructure during short-term storage, depending on the instability mechanism. The compression behaviour of particles prepared by crystal agglomeration and wet granulation was dependent on their degree of agglomeration and their failure strength. For particles with similar solid state properties and compression behaviour, the surface energy appears to have an effect on the bonding strength of adsorption bonds acting at interparticulate junctions. Using the method developed to observe the drug release from single matrix granules, reproducible data was obtained enabling the drug release process to be characterised. Depending on the type of matrix and the compaction pressure, the drug release rate could be enhanced or retarded.

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