Gohil, Virajsinh Ranjitsinh; (2008) Investigation into the effect of surface induced disorder on the granulation characteristics of hydrophobic actives. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The purpose of this study was to initially understand and characterise process induced transformations in hydrophobic actives and the impact upon granulation. High energy pharmaceutical processing can often lead to changes in the crystalline form and can impact upon the final formulation of the product. It is highly important that these changes in the crystallinity can be quantified and measured. Initially a technique was undertaken to characterise the amorphous content of micronised samples. The RH perfusion isothermal microcalorimeter technique was used to quantify <5 % levels of disorder in the micronised active and then this technique was used to study how variables during milling such as the feed pressure and milling time can impact upon the crystallinity of these actives. The surface transformations were also investigated using Inverse Gas Chromatography. Surface energetic data was analysed to determine the changes during processing and the changes that occur during storage of the active with an increase in the relative humidity and time. The energetic changes were studied for the two hydrophobic active to understand the impact of processing and how the active may interact during granulation. The actives were granulated and the granule characteristics were correlated to the surface energetic data and the isothermal microcalorimetry data. The investigations yielded interesting results that indicated variability and changes in the granular distributions as a result of micronisation. Granule data such as friability of granules and the distribution of the particle sizes gave an insight into the changes that occur to the granulation system.

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