Preparation and Characterization of Salbutamol Sulphate Loaded Ethyl Cellulose Microspheres using Water-in-Oil-Oil Emulsion Technique

The aim of this study was to formulate and evaluate microencapsulated controlled release preparations of a highly water/soluble drug, salbutamol sulphate by (water in oil) in oil emulsion technique using ethyl cellulose as the retardant material. Various processing and formulation parameters such as drug/polymer ratio, stirring speed, volume of processing medium were optimized to maximize the entrapment. The release of salbutamol sulphate from ethyl cellulose microsphere was compared and possible release mechanism proposed. Microspheres were prepared by water in oil emulsion technique using acetonitrile/dichloromethane (1:1 ratio) solvent system. Span 80 was used as the dispersing agent and n-hexane was added to harden the microspheres. The prepared microspheres were characterized for their micromeritic properties and drug loading, as well as compatibility by infrared spectroscopy, differential scanning calorimetry (DSC), X-ray powder diffractometry and scanning electron microscopy (SEM). The in-vitro release studies were carried out in phosphate buffer at pH 7.4. The prepared microspheres were white, free flowing and spherical in shape. The drug-loaded microspheres showed 55.7 - 76.6 % of entrapment and release was extended up to 10 h. Various processing and formulation parameters such as drug/polymer ratio, stirring speed, volume of processing medium, etc. significantly affect the drug release from the microspheres. The best/fit release kinetics was achieved with Higuchi plot followed by zero order and first order. The release of salbutamol sulphate was influenced by altering the drug to polymer ratio and the drug release was found to be diffusion controlled.