Differential Scanning Calorimetric Analysis for Incompatibility: Sodium Stearate/Magnesium Stearate and Acidic Compounds

Compatibility investigation was performed between stearate lubricants (sodium stearate and magnesium stearate) and acidic pharmaceutical compounds (ibuprofen, indomethacin and valproic acid) and citric acid as acidic pharmaceutical excipient using differential scanning calorimetry (DSC). Alteration in DSC thermogram was found in all mixtures. There was a presence of melting endothermic peak of stearic acid in all mixtures (except that of stearate lubricants and indomethacin) indicating breakage of salt form of stearate lubricants depended on the physicochemical properties of drug compounds and pharmaceutical excipient. Therefore, the avoidance for using stearate lubricants with acidic pharmaceutical compounds and excipient should be concerned in development of pharmaceutical formulations.