Transdermal device

A method of preparing a device for transdermal delivery of an active ingredient which is a solid at room temperature and in which part or all of the active ingredient is present in a supersaturated solution comprising the steps of:

• (a) preparing a mixture comprising at least:
• (i) a polymer adhesive which is selected from the group consisting of acrylate polymer adhesives, polyisobutylene adhesives, and silicone adhesives;
• (ii) a vehicle for the polymer adhesive, which vehicle is selected from the group consisting of water, ethanol, industrial methylated spirits, isopropanol, toluene, xylene, methylene chloride, and chlorofluorocarbon;
• (iii) the active ingredient;
• (iv) a solvent mixture for the active ingredient which comprises at least two solvents having different boiling points;
• (b) forming the mixture prepared in step (a) into a film, and
• (c) drying the film prepared in step (b),
• wherein the vehicle for the polymer adhesive and at least one of the solvents in the solvent mixture for the active ingredient have boiling points below the drying temperature, and at least one of the solvents in the solvent mixture for the active ingredient has a boiling point above the drying temperature, and wherein the solubility of the active ingredient in the said solvent or solvents having a boiling point above the drying temperature is greater than 10%.