The release of caffeine from hydrogenated and fluorinated gel emulsions and cubic phases

A comparative study of the caffeine release from concentrated emulsions and cubic phases, formulated on the basis of fluorinated and hydrogenated oils and surfactants, has been carried out. A very important (20-fold) prolonged effect has been found for the fluorinated-emulsions with regards to the hydrogenated one that is explained by the specific properties of fluorinated surfactants (e.g., much higher cohesion energy of adsorption monolayers) as well as by the effect of other physico-chemical parameters (interfacial tension and specific area of adsorption monolayers, interaction of a drug with the surfactants, partition coefficient etc.). The release properties of the caffeine from different thermodynamically or kinetically stable self-organized systems, cubic phases and gel emulsions have been compared with the structural and rheological properties of these systems. The effect of salt on both, release rate of caffeine and rheological properties of these systems, has been discussed. (C) 2004 Elsevier B.V. All rights reserved.