The objective of the present work is to study the dissolution behavior of olanzapine from its solid dispersions with mannitol. Solid dispersions were prepared by melt dispersion method and characterized by phase solubility studies, drug content and in vitro dissolution studies. The best releasing dispersions were selected from release data, dissolution parameters and their release profiles. Solid state characterization techniques like Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometry, differential scanning calorimetry, near-infrared and Raman spectroscopy were used to characterize the drug in selected dispersions. The dispersions were also evaluated by wettability studies and permeation studies. The results of phase solubility studies and the thermodynamic parameters indicated the spontaneity and solubilization effect of the carrier. The release study results showed greater improvement of drug release from solid dispersions compared to pure drug, and the release was found to increase with an increase in carrier content. The possible mechanism for increased release rate from dispersions may be attributed to solubilization effect of the carrier, change in crystal quality, phase transition from crystalline to amorphous state, prevention of agglomeration or aggregation of drug particles, change in surface hydrophobicity of the drug, and increased wettability and dispersability of the drug in dissolution medium. The suggested reasons for increased release rate from dispersions were found to be well supported by results of solid state characterization, wettability and permeation studies. The absence of any interaction between the drug and the carrier was also proved by FT-IR analysis.
Olanzapine; Mannitol; Solid dispersions
