Abstract

Purpose: To characterize and investigate the in-vitro drug release behavior of a chitosan-magnesium stearate monolithic system. Methods: A monolithic system consisting of chitosan and magnesium stearate was prepared by direct compression to provide sustained release of propranolol HCl in a pH change system. Least squares fitting of the experimental dissolution data to the mathematical expressions (power law, first-order, Higuchi equation and zero-order) was carried out to study the drug release mechanism. FT-IR, DSC and powder X-ray diffraction were used to characterize the matrix component. Results: An increased amount of magnesium stearate retarded the drug release. Incorporation of malic acid and xanthan gum affected the drug release characteristics. The drug release was apparently slower when the amount of matrix was increased. FT-IR, powder X-ray diffraction and DSC studies showed a charge interaction between the NH₃⁺ of the chitosan molecule and the COO^- groups of the magnesium stearate. The SEM images revealed the formation of a porous structure that was due to the dissolution of the matrix component after gel formation by matrix relaxation following absorption of the dissolution medium. Conclusion: The interpolyelectrolyte complex from the monolithic system consisting of chitosan and magnesium stearate offered sustained the drug release.


Keywords:  Monolithic matrix   Chitosan   Magnesium stearate   Drug release