Some physico-chemical factors affecting the release of salicylic acid and related drugs from oil-in-water emulsions

Abstract

The stability and release characteristics of some Miglyol-in-water emulsions were studied. The ternary phase diagrams of Miglyol, water and the selected anionic, cationic and non-ionic surfactants provided fundamental information about the stability of the emulsions produced. The preliminary drug release experiments indicated that release from an emulsion was governed by the transfer of the drug from the oil phase, which was dependent on the type of the interfacial film. This was proved using different surfactants or surfactant mixtures to prepare the emulsions. The effect of the apparent partition coefficient.of the drug, which is a function of the oil/water phase volume ratio, ø, the micellar phase concentration and the pH of the external phase, on release was studied. The release wass lower the greater the ø or , for the same ø, the higher the micellar phase concentration. The effect of the partition coefficient on drug release was demonstrated, by incorporating different drugs in a model emulsion which showed that these two parameters are inversely related. A trend towards a decreasing release rate from the oil with increasing viscosity was observed . However, the variations observed in the drug release from the emulsions could not only be attributed to the viscosity of the oil phase, but also to the changes in the interfacial film caused by the gelling agents. The short and long-term and the elevated stability tests proved that, except in the case of emulsions stabilized with Span 80 or Tween 20-Span 80 mixtures to produce low HLB values, the emulsions were stable . However, particle size distribution analysis determined by photosedimentometry has confirmed that microscopy was not a satisfactory method for accurate size distribution analysis and it provided only a gross visual check on the size distribution. This was due to the presence of a large number of globules in the submicrometer range.

Date of Award	Jan 1983
Original language	English
Awarding Institution	University of Brighton