Prediction of the stability of polymeric matrix tablets containing famotidine from the positron annihilation lifetime distributions of their physical mixtures

The aim of the present work was to elucidate the impact of the structural changes of polymeric excipients during the course of storage on the drug release stability of tablets containing different polymers. Matrix tablets were formulated with famotidine as a model drug, using polyvinylpyrrolidone and carbopol matrix. Dissolution tests were carried out before and after storing the tablets under stress conditions for different time intervals. Parameters characterizing the release kinetics of matrix tablets, just as difference and similarity factors, were calculated to compare the release profiles as a function of storage time. Positron annihilation lifetime measurements were carried out to track the structural changes of the physical mixtures containing polymers during the course of storage. The changes in the positron lifetime distribution curves of the famotidine-polymer mixtures were in good correlation with the significant changes of release parameters of tablets. Thus the method would be a valuable tool for the screening of possible destabilizing interactions in the preformulation phase.