A loperamide simethicone combination formulation has recently been demonstrated to have significant clinical advantages compared to loperamide alone in the relief of diarrhoea and related symptoms. The product visualisation technique of gamma scintigraphy has been used to investigate the interaction of the formulation with the heterogenous environment of the human gut in a group of 12 healthy volunteers. The results suggest that changes in the intestinal kinetics of loperamide from the combination product, e.g. jejunal coating, could be contributing to the improved efficacy.