Effect of Dispersing Agent on the Characteristics of Eudragit Microspheres

Eudragit RS microspheres containing Indina vir sulphate for oral use were prepared using two different dispersing agents: aluminium stearate and magnesium stearate, by solvent evaporation method. The effects of the type and concentration of the dispersing agents and the inner phase polymer concentration on the size of microspheres was studied. The morphology of microspheres was characterized by scanning electron microscopy. The surface of microspheres prepared with aluminium stearate was smoother and non-porous. When magnesium stearate was used as dispersing agents, the particle size of microspheres decreased. Increasing amounts of this dispersing agent led to the accumulation of their free particles onto the surfaces of the microspheres. The drug release from the microspheres was faster with the microspheres from aluminium stearate based on their hydrophobic structures. The encapsulation efficiency is more in case of aluminium stearate in comparison to magnesium stearate. Formulation containing aluminium stearate shows a more sustained effect than formulation containing magnesium stearate. This may due to fact that aluminium stearate is more hydrophobic in comparison to magnesium stearate.