The influence of excipient particle size, solubility and acid strength on the dissolution of an acidic drug from two-component compacts

The dissolution properties of mixed compressed discs containing ibuprofen and one of three different acid excipients were investigated and the effect of various processing variables examined. Ibuprofen dissolution rate was shown to change depending on the acid excipient particle size used, the solubility of the excipient and its acid strength. Decreasing the excipient particle size resulted in a lowering of the ibuprofen dissolution rate. A decrease of an order of magnitude up to 20-fold could be achieved when smaller sized excipient particles were used. The observed dissolution phenomena associated with changing excipient particle size were explained in terms of percolation theory and dissolution from pores of a dimension similar to or larger than that of the aqueous boundary layer. It was also observed that the stronger the acid used as the excipient and the greater its solubility, the greater was its suppressing effect on the dissolution rate of the drug.