The invention relates to an oily pharmaceutical composition based on peroxidized lipids and on silica, characterized in that it contains, as essential constituents, peroxidized lipids which have a degree of peroxidation of between 5 and 600 milli-equivalents per kilogram, and silica which is dispersed within said peroxidized lipids at a concentration of greater than or equal to 0.5% by weight and less than 4% by weight with respect to the weight of said composition. In this composition, the peroxidized lipids are preferably obtained by peroxidation of a natural plant oil and the silica is preferably colloidal silica. The invention also relates to the use of the composition for the preparation of a pharmaceutical composition which is intended for treating xerostomia.