It is intended to provide a transdermal absorption preparation capable of sustaining the blood morphine concentration at the effective level over at least 48 hours, etc. This transdermal absorption preparation comprises a medicinal composition for transdermal absorption in which an active ingredient selected from among morphine and salts thereof is blended in such an amount as corresponding to the saturation solubility or more with an active ingredient-holding vehicle having fluidity at a temperature around the human skin surface temperature and at least a portion of the active ingredient is held as crystals, characterized in that, in the case where a preparation obtained from the above-described medicinal composition for transdermal absorption is applied to the uninjured back of a white rabbit having been shaven with electrical clippers for 72 hours, the available dose of the active ingredient per single dose of the preparation is from 10 mg to 400 mg in terms of morphine base, and the plasma concentrations of the active ingredient 24 hours and 48 hours after the application of the preparation under the above-described conditions are each at least 40 ng/mL in terms of morphine base, and so on.本發明的目的在於提供一種經皮吸收製劑,使用該經皮吸收製劑時,嗎啡的有效水平的血藥濃度能够持續至少48小時。該經皮吸收製劑含有經皮吸收醫藥組合物等,所述經皮吸收醫藥組合物中,選自嗎啡或其鹽的有效成分以飽和溶解度以上的混合量混合在於接近人皮膚表面溫度的溫度下具有流動性的有效成分保持用介質中,並且該有效成分的至少一部分以結晶型存在,所述經皮吸收醫藥組合物的特徵在於,將所述經皮吸收醫藥組合物製劑化,並將其在用理髮推子進行了剪毛處理的白色家兔的無傷的背部皮膚上應用72小時時的製劑單次用劑量中該有效成分的可利用量按嗎啡碱換算爲10mg~400mg,並且,在上述條件下應用製劑後24小時和48小時時,該有效成分在血漿中的濃度按嗎啡碱換算至少爲40ng/mL。
