EFFECT OF MAGNESIUM STEARATE ON CHITOSAN MICROSPHERES PREPARED BY AN EMULSIFICATION-COACERVATION TECHNIQUE

Chitosan microspheres were prepared using an emulsification-coacervati on technique. The w/o emulsion comprised a mixture of light and heavy liquid paraffins containing sodium dioctyl sulphosuccinate as the oil phase and chitosan solution as the aqueous phase. Pentasodium tripolyp hosphate was included as a counterion. The chitosan microspheres obtai ned showed a high degree of aggregation. This was markedly reduced, by the incorporation of magnesium stearate in the disperse phase. The re sultant microspheres were then discrete, spherical with smooth surface s. Additionally, with an increasing magnesium stearate content, larger -sized microspheres were produced. The DSC analysis data suggested tha t the magnesium stearate was converted to stearic acid during the prep aration process. Chitosan microspheres containing propranolol hydrochl oride were similarly prepared, but their surface was convoluted and th eir shape not well defined. Unlike the microspheres without drug, the size of the drug-loaded microspheres decreased with increasing magnesi um stearate content. The release of propranolol hydrochloride from the microspheres was fast, irrespective of the content of magnesium stear ate. Drug encapsulation efficiency was enhanced when a greater amount of magnesium stearate was used.