Solvent and surfactant induced interactions in drug dispersions

The interaction between Salbutamol base and Salbutamol sulphate drug particles with a number of non-aqueous and mixed liquids is investigated. The non-aqueous liquids extend form hydrocarbon to halo-hydrocarbon liquids, including propellant liquids previously used in Metered Dose Inhalers. The properties are correlated using two commonly used solvent scales, the Hamaker constant and Solubility parameter scales. The focus is laid on evaluating their relationship to the effective surface charge (ζ-potential), the particle size and their capability to predict the solubility of the drugs. The influence of a standard surfactant, oleic acid on the chosen properties is another topic of key interest. The stability of the dispersions was successfully predicted by the Coulomb interaction model of Morris.