An object of the present invention is to provide a patch preparation having an excellent skin permeability of a medicament, comprising an acid addition salt of a basic medicament as a raw material. Provided is a patch preparation comprising a support and an adhesive layer on one surface of the support, wherein the adhesive layer contains a basic medicament, a fatty acid-based ionic liquid, and a potassium salt and/or potassium ion. The potassium salt and/or potassium ion are generated as a result of reaction of an acid addition salt of the basic medicament with a compound capable of generating potassium ion in the adhesive layer.Examples of the basic medicament include an opioid pain reliever, and examples of the acid addition salt include hydrochloride salt.
