Pharmaceutical preparations having an improved solubility

The present invention provides a method for producing a pharmaceutical preparation having an improved solubility, which comprises the steps of forming a micelle by dissolving a poorly-soluble drug having the ability to form the micelle into water; and fixing the micelle structure which is formed with the poorly-soluble drug, by using a compound(s) which fixes the micelle structure. This production method preferably further comprises the step of adjusting the pH back to neutral and/or cooling down the temperature to room temperature after fixing the micelle structure. The poorly-soluble drug which is the subject of the above method is such as those forming a micelle in water only when heated and/or in the presence of an acid(s) or alkali(s). According to this production method, it can produce a pharmaceutical preparation having an improved solubility, which makes possible to accomplish the improvement of oral absorbability of a poorly-soluble drug(s).