A patch comprising a support layer and an adhesive layer, wherein the adhesive layer comprises diclofenac sodium, dimethyl sulfoxide, and citric acid a mass ratio between the diclofenac sodium and the citric acid (mass of diclofenac sodium : mass of citric acid) is 1:0.15 to 1:0.45 and a mass ratio between the diclofenac sodium and the dimethyl sulfoxide (mass of diclofenac sodium : mass of dimethyl sulfoxide) is 1:0.75 to 1:3.
