Inclusion and release of theophylline from chitosan based microparticles

Chitosan (CS) based microparticles for controlled release of theophylline (THP) were obtained by ionic gelation. The microparticles were characterized by laser diffraction analysis (particle size), scanning electron microscopy (SEM), FTIR spectroscopy, and thermogravimetric analysis. The average diameter of the CSTHP microparticles was 182 μm. The FTIR spectra confirmed that new hydrogen bonds had formed between the carbonylic group belonging to THP and the amino group of CS, while the thermogravimetric analysis showed a modified stability in the obtained particles and confirmed the presence of an interaction between the drug and CS. The THP release process was monitored for up to 24 h in simulated gastric fluid (pH 1.5) and in simulated intestinal fluid (pH 7.4). The release process of THP from microparticles was not influenced by the pH of dissolution media. In the first 30 min the drug was released in a rapid manner, and after this stage by a non-Fickian profile.