Study of the stability of Kollidon® SR suspensions for pharmaceutical applications

Currently, great efforts are devoted to the design of drug delivery systems and many new polymers are investigated to make drug release fit the desired profiles. In this work, we investigate the formulation of colloidal aqueous suspensions based on the polymer Kollidon® SR for the oral administration of drugs. Such an investigation has never been carried out to our knowledge, as this polymer has only been used as soluble binder and film-forming agent for solid dosage forms. In this work, both the stability and redispersibility characteristics of Kollidon® SR aqueous suspensions are extensively investigated through thermodynamic and electrokinetic studies. The hydrophilic character of the polymer, and the surface charge and electrical double layer thickness play a key role in the stability of the suspensions, hence the need for a full characterization of the polymer. Kollidon® SR suspensions display a “free-layered” sedimentation determined by their hydrophilic character and their zeta potential values (indicating the electrokinetic charge on the particles). The electrostatic repulsion between the particles is responsible for the low sedimentation volume and easy redispersibility of the polymer.