Encapsulation of 5-aminosalicylic acid into Eudragit RS microspheres and modulation of their release characteristics by use of surfactants

Abstract

An emulsification-solvent evaporation technique has been used to produce microspheres containing 5-aminosalicylic acid from the acrylate-methacrylate copolymer, Eudragit TM RS. Two emulsifiers were used in the preparation procedure, either sodium dodecyl sulphate (SDS) or Tween 20, at a range of concentrations. Microspheres could be produced with both surfactants, although the yield using SDS was very low. The rate of drug release was found to be dependent on the concentration of emulsifier used to produce the microspheres. For example, microspheres produced using 0.25% w/v SDS released their encapsulated drug instantaneously on dissolution testing, whereas microspheres produced without surfactant provided prolonged release of drug ( t 50% > 360 min). Low temperature scanning electron microscopy revealed for these two systems that the differences in release resulted from different degrees of porosity in the microsphere drug-polymer matrix.