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Title: A Physico-Chemocal Investigation into the Factors Affecting the Behaviour of Self-Emulsifying Drug Delivery Systems
Author: Mercuri, Annalisa
ISNI:       0000 0004 2688 9709
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2009
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The aim of this work was to investigate the relationship between drug-loading and self-emulsification. Several techniques were used to assess the physico-chemical properties of a self-emulsifying formulation formed by GRAS listed excipients with and without a model drug. The micropolarity at the droplet interface was found to be related to the HLB of the surfactant mixtures and it was shown to increase when the drug ibuprofen (6% w/w) was present. IH-NMR showed that this is due to the preferred solubilisation site of the drug; in fact, surfactant-like drugs preferably solubilise at the palisade layer formed by polyoxyethylene units. Phase diagrams showed that the model drug ibuprofen altered the liquid crystal distribution within the SEDDS. Low frequency dielectric spectroscopy confirmed this relationship between drug-loading and phase changes upon dilution. An attempt to correlate in vitro systems with the in vivo scenario was made by measuring the droplet size of the placebo and ibuprofen formulation (6% w/w) using volumetric flask, dissolution apparatus 2 and the novel in vitro Dynamic Gastric Model, DGM (Institute of Food Research, Norwich, UK). The droplet size measured was found to be dependent on media, system used and presence of the drug. Data obtained were compared with the micropolarity of the SEDDS droplets obtained by pyrene fluorescence, and were found to be in good agreement. Furthermore, the results obtained with the DGM showed a clear relationship between digestion and droplet size, with the drug-loaded formulation being more stable than the placebo, which was shown to increase its size as digestion proceeded. The impact of drug loading within a SEDDS was shown to influence the formulation performance significantly. The behaviour of a SEDDS in vivo can not be satisfactorily described by conventional in vitro systems, as it is highly dependent on the motility, biochemistry and physiology of the digestive system.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available