Formulation of controlled-release baclofen matrix tablets II:: Influence of some hydrophobic excipients on the release rate and in vitro evaluation

The aim of this study was to investigate the influence of polymer level and type of some hydrophobic polymers, including hydrogenated castor oil (HCO); Eudragit RS100 (E-RS100); Eudragit L100 (E-L100), and some fillers namely mannitol [soluble filler], Dibasic calcium phosphate dihydrate (Emcompress) and anhydrous dibasic calcium phosphate [insoluble fillers] on the release rate and mechanism of baclofen from matrix tablets prepared by a hot-melt granulation process (wax tablets) and wet granulation process (E-RS100 and E-L100 tablets). Statistically significant differences were found among the drug release profile from different classes of polymeric matrices. Higher polymeric content (40%) in the matrix decreased the release rate of drug because of increased tortuosity and decreased porosity. At lower polymeric level (20%), the rate and extent of drug release was elevated. HCO was found to cause the strongest retardation of drug. On the other hand, replacement of Emcompress or anhydrous dibasic calcium phosphate for mannitol significantly retarded the release rate of baclofen, except for E-L100 (pH-dependent polymer). Emcompress surface alkalinity and in-situ increase in pH of the matrix microenvironment enhanced the dissolution and erosion of these matrix tablets. The release kinetics was found to be governed by the type and content of the excipients (polymer or filler). The prepared tablets showed no significant change in drug release rate when stored at ambient room conditions for 6 months.