LAUSR

The use of the surfactant, sodium lauryl sulfate (SLS), instead of enhancing drug dissolution, deteriorates the dissolution of some alkaline drugs through forming poorly soluble lauryl sulfate salts. The thermodynamic driving force for precipitation of such salts is the ratio of ion product in solution (Q) to the solubility product of the salt (Ksp). In this work, we have examined two formulation strategies for mitigating the negative effect of SLS on the dissolution of p-aminobenzoic acid (PABA) by reducing the Q value of its LS salt in the diffusion layer: 1) introducing alkalizing excipient, Na3PO4, to reduce the concentration of PABAH+ by elevating the microenvironment pH, and 2) introducing NaCl to reduce the LS- monomer concentration by depressing the critical micelle concentration (CMC) of SLS.