Estimation of Excipient Percolation Threshold

As explained in previous sections, the percolation threshold corresponds to the concentration of a component for which there is a maximum probability of appearance of an infinite or percolating cluster of this component. 

Sample Bulk Density (g/ml) Tappped Density (g/ml) Hausner lndex Carr lndex (%) Sponginess lndex Flowability (g/s) Rest Angle ( ) 

Below the percolation threshold, the excipient does not percolate the system and the drug release is not as efficiently controlled by the gel layer. In this situation, the gel layer initially shows important holes which allow a fast water uptake, leading to a quicker release process. By contrast, above the excipient percolation threshold (lots containing 20 and 30% of polymer) a percolating cluster of this component exists and a coherent gel layer is formed from the first moment, which is able to control the hydration and drug release rate. 

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Estimation of Excipient Percolation Threshold. In principle, for binary pharmaceutical systems, two percolation thresholds are expected the drug percolation... 

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