The present invention provides a pharmaceutical preparation that significantly reduces leakage of a low-molecule medicine in a strong acidic environment, while allowing release of the low-molecule medicine in the enteric canal or the like which is in a weak acidic to neutral environment. The S/O type pharmaceutical preparation of the present invention is characterized in comprising a medicine-containing complex dissolved or dispersed in an oil phase, wherein the complex contains a mixture and a surfactant, the mixture is covered by the surfactant, and the mixture contains a hydrophilic low molecule medicine, and a hydrophilic medicine-leakage-suppressive protein and/or a medicine-leakage-suppressive polysaccharide.