A new wet conductivimetric method to estimate the drug percolation threshold.

Abstract

The main objectives of this work are to study the behavior of fluid imbibition into a consolidated matrix through a wet invasive conductivimetric technique, to investigate if the changes in the behavior observed can be related to the drug percolation threshold, and to use this technique for its estimation. Matrix tablets were prepared using five sieving fractions of KCl and Eudragit RS-PM. In vitro release assays were carried out on 45 batches. The drug percolation thresholds were estimated following the method of Leuenberger and Bonny, and the results were compared to the obtained employing the conductivimetric technique described in this paper. The wet conductivimetric technique and the standard method provided similar results for the estimation of the percolation threshold. The presented technique also provides quantitative information about the consolidated matrix. A new apparatus has been developed for the study of the conductivimetric behavior of matrix tablets during water uptake. This technique provides measurable parameters of fluid penetration and can be used to estimate the drug percolation threshold, providing similar results to the Leuenberger and Bonny method and being clearly faster.