Patch and method for producing the same

A method for producing a patch comprising a support layer and an adhesive agent layer arranged on at least one surface of the support layer, the method comprising:

• obtaining an adhesive agent layer composition comprising
• at least one drug which is free oxybutynin,
• an acrylic-based polymer and a rubber-based polymer as an adhesive base agent,
• liquid paraffin,
• an organic acid, and
• a tackifier;
• heating the adhesive agent layer composition at a temperature in a range from a melting point (° C.) of the drug to a temperature higher than the melting point by 10° C. for 8 to 24 hours;
• and
• cooling the heated adhesive agent layer composition to a temperature lower than the melting point of the drug at an average rate of temperature drop of 1 to 20° C./hour, thereby obtaining the adhesive agent layer comprising the drug at a supersaturated concentration in a dissolved form, wherein
• a content of the oxybutynin in the adhesive agent layer composition in terms of free oxybutynin is an amount which results in 10 to 50% by mass in the obtained adhesive agent layer,
• the adhesive agent layer composition comprises, as the adhesive base agent, the acrylic-based polymer and the rubber-based polymer at a mass ratio of 1:4 to 1:19, and
• a mass ratio of the oxybutynin to the liquid paraffin is 0.5:1 to 1.2:1 in the adhesive agent layer composition.