Dissolution testing of amorphous solid dispersions.

The main purpose of this study was to investigate the effect of different polymers, with varying physicochemical properties and molecular weight on the stability and dissolution of co-milled amorphous solid dispersions (ASDs) of piroxicam (PRX). The stability of amorphous PRX (aPRX) in ASDs was significantly improved by the polymers. In-line Raman spectroscopy revealed that solvent mediated solid state changes occurred in biorelevant medium, however differences between ASDs were found. Thus, the dissolution behavior of ASDs of PRX and the respective polymer during conventional large volume (900ml) and a commercial small volume (20ml) dissolution testing was evaluated. The results of these studies indicated that the molecular weight of the polymer (PVP90 vs PVP25) is influencing the solubility of PRX from ASD. Interestingly the effect of molecular weight of the polymer was different than reported previously in the literature for the similar ASDs prepared by spray drying. Furthermore, the dose related bioavailability was determined by investigating the experimental saturation concentrations for different doses. These studies confirmed the findings of the dissolution studies. The differences are presumably caused by the formation of physically different diffusion layers around the ASD particles.