The aim of the present study was to evaluate the influence of magnesium aluminometasilicate (Neusilin US2) on ibuprofen stability at higher temperatures. Seven binary mixtures of the drug and the silicate were prepared. They were examined by thermogravimetry (TGA), quadrupole mass spectrometry (QMS) and differential scanning calorimetry (DSC). The results confirmed that in the presence of the magnesium aluminometasilicate ibuprofen free acid reacted to form a higher melting, less volatile salt. The presence of the salt was additionally confirmed by FT-IR and H NMR spectra. It leaded to the conclusion that Neusilin US2 had a beneficial effect on the drug stability. The drug to silicate ratio to protect the highest amount of the drug from evaporation by using the lowest amount of the excipient was found to be 40:60 and 50:50 weight percent. (C) 2010 Elsevier B.V. All rights reserved.