Influence of two different types of excipient on drug percolation threshold

Abstract

The application of the principles of percolation theory is providing a more rational pharmaceutical dosage form design. The drug percolation threshold is the parameter that provides a better description of the system according to this theory. In order to check the possibility of use the drug percolation threshold as a preformulation parameter, the influence of the main formulation factors is being studied. The aim of this work is to study the influence of the type of excipient on the drug percolation threshold. For this purpose, two excipients exhibiting very different mechanical behaviour have been selected. Inert matrices were prepared using Ethocel® 100 and Eudragit® RS-PM as excipients and KCl as a model drug. Release assays were performed using the rotating disk method. The drug percolation threshold was estimated employing the method of Leuenberger and Bonny. The following confidence intervals (95%) were obtained: ϵ c=0.3644±0.0641 and ϵ c=0.3407±0.0345 of total porosity for matrices containing Eudragit® RS-PM and Ethocel® 100, respectively. On the light of the obtained results, no significant differences were found on the drug percolation thresholds for two excipients having very different mechanical behaviour.