Investigation of Carnuba Wax as Matrix in the Formulation of Solid Lipid Microparticles for Controlled Release Application
This study was carried out to investigate the drug entrapment efficiency, release potential and drug release mechanisms of solid lipid microparticles (SLMs) prepared with different concentrations of two non ionic surfactants using carnauba wax as the lipid matrix. SLMs were prepared by melt dispersion technique, whereby the molten carnauba wax containing the drug (theophylline) was emulsified in heated aqueous phase with different concentrations of non ionic surfactants, followed by cooling at room temperature for recrystallization of the microparticles, which were recovered. The prepared SLMs were characterized for their packing, flow properties, drug entrapment efficiency and encapsulated for dissolution testing. The dissolution data were analysed using zero order, first order and Higuchi drug release models. It was observed that all the SLMs prepared had a high drug entrapment efficiency >80%. Increase in surfactant concentration decreased the drug entrapment efficiency although the type of non ionic surfactant used had no significant effect on the drug entrapment efficiency (p>0.05). The drug release profile followed first order as well as Higuchi square root of time models. The results of this study show that it is possible to formulate SLMs with high drug entrapment efficiency when carnauba wax is used as lipid matrix. These prepared SLMs can be used effectively to modulate release of theophylline which will in turn improve patient compliance.
Keywords: Solid lipid microparticles, drug entrapment efficiency, non ionic surfactants, drug