Anomalous Water-Sorption Kinetics in ASDs.

Area of Science:

• Materials Science
• Physical Chemistry
• Pharmaceutical Sciences

Background:

• Anomalous water-sorption kinetics in amorphous solid dispersions (ASDs) are primarily attributed to the slow swelling of the polymer matrix.
• Understanding these kinetics is crucial for predicting drug release from ASDs.

Purpose of the Study:

• To predict the anomalous water-sorption kinetics in poly(vinyl-pyrrolidone)-co-vinyl-acetate (PVPVA) and indomethacin (IND) ASDs using a diffusion-relaxation model.
• To elucidate the underlying mechanisms causing anomalous water sorption in these ASDs.

Main Methods:

• Utilized a diffusion-relaxation model incorporating the Williams-Landel-Ferry (WLF) and Arrhenius equations.
• Model predictions were based on the viscosities of pure PVPVA, pure IND, and water-sorption kinetics of pure PVPVA.
• Compared model predictions with experimental data for qualitative and quantitative agreement.

Main Results:

• The diffusion-relaxation model successfully predicted various types of anomalous water-sorption behavior in ASDs.
• ASDs exhibited more pronounced anomalous two-stage water-sorption than pure PVPVA.
• Higher viscosity of glassy ASD-water mixtures compared to PVPVA-water mixtures was identified as the cause for slower swelling.

Conclusions:

• The developed modeling approach accurately captures anomalous water-sorption kinetics in ASDs.
• The study highlights the significant impact of polymer swelling dynamics on water sorption in ASDs.
• This modeling strategy can be applied to predict diffusion- or swelling-controlled drug release from ASDs.