Sutananta, Wanchai; (1993) The physical characterisation of complex glyceride mixtures. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Gelucires, which are the glyceride-based pharmaceutical excipients, may be used as matrix forming materials to control the drug release from dosage forms such as molten filled hard gelatin capsules. A knowledge of the effects of manufacturing conditions on the physical properties of the bases is important for controlling product performances. The morphological, thermal, mechanical, rheological and dielectric properties of a range of gelucires with various melting points and HLB values prepared by different cooling rates were then examined. In addition, the changes of the physical properties of the bases after ageing for various periods of time were monitored. The release characteristic of a model drug, theophylline, from the bases was also studied. Examination by differential scanning calorimetry indicated that slow cooling allowed fractional crystallisation of various components in the bases while fast cooling resulted in the bases that extensively form solid solutions. The cooling rates also affected the crystallisation of stable and unstable polymorphic forms of glycerides. As a result of these microstructural differences, the physical properties such as morphological, thermal, mechanical (in term of tensile strength) and dielectric properties, of the slowly and fast cooled bases were different. Polymorphic transformation of glyceride components in the bases occurred during storage, leading to the change in their microstructures and hence their physical properties. The release of theophylline from gelucire matrices was found to be either diffusional or erosion-diffusional controlled. The PEG esters in gelucires could attract water into the matrices and dissolve or swell thus creating channels for drug diffusion or causing erosion of the matrices. Cooling rate also affected the release of the drug from some gelucire matrices. The rate of drug release from the bases also changed during storage as a result of microstructural change or the degradation of the bases. Moisture accelerated the change in the release rate since it influenced the structural change and the degradation of gelucires.

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