The effect of composition and gastric conditions on the self-emulsification process of ibuprofen-loaded self-emulsifying drug delivery systems: A microscopic and dynamic gastric model study

Purpose: To investigate the physical processes involved in the emulsification of self-emulsifying drug delivery systems (SEDDSs) and the use of the Dynamic Gastric Model (DGM) as a characterisation tool. Methods: SEDDSs based on soybean oil, Tween 80, Span 80 and ibuprofen were prepared and their equilibrium phase diagrams established. The emulsification behaviour in a range of media was studied using polarised light microscopy and particle sizing. The behaviour of the SEDDSs in the DGM and conventional testing equipment was assessed. Results: A range of liquid crystalline mesophases was observed, enhanced in the presence of the drug. Polarised light microscopy showed different emulsification processes in the presence and absence of the drug, which was also manifest in different droplet sizes. The droplet size distribution varied between the DGM and the USP II dissolution apparatus. Conclusions: The model SEDDS displays complex liquid crystalline behaviour which may be intimately involved in the emulsification process, which in turn may alter particle size on emulsification, although there remains a question as to the in vivo significance of this effect. Furthermore, we demonstrate that the DGM represents a very promising new method of assessing the biological fate of SEDDSs.