An object of the invention is to combine a plurality of drugs having different physical properties in a single dosage form by modifying surface properties from hydrophilic to lipophilic or vice versa. A drug-surfactant composite comprising drugs enclosed by a surfactant is produced, and the resulting drug-surfactant composite is microdispersed in a hydrophilic solvent to prepare an S/W preparation, the resulting drug-surfactant composite is dispersed in a fat-soluble solvent to prepare an S/O preparation, or the S/W or S/O preparation is further dispersed in a hydrophilic solvent to prepare an S/O/W preparation. This enables a combination of a plurality of drugs in the same dispersion medium.
