The present invention relates to 2- (4-ethyl-1-piperazinyl) -4- (4-fluorophenyl) -5,6,7,8,9,10-hexahydrocycloocta [b] pyridine (active ingredient). An oral preparation that is stable and has good dissolution behavior in a wide pH range, contains an active ingredient and a solubilizing agent, and performs the dissolution test described in the 15th revised Japanese Pharmacopoeia. It is an oral solution whose dissolution rate after 15 minutes from the start of the test is 50% or more.本発明は、２－（４－エチル－１－ピペラジニル）－４－（４－フルオロフェニル）－５,６,７,８,９,１０－ヘキサヒドロシクロオクタ［ｂ］ピリジン（活性成分）を安定に含有し、広いｐＨ領域で良好な溶出挙動を示す経口製剤であって、活性成分及び溶解補助剤を含有し、第１５改正日本薬局方に記載の溶出試験を行うとき、溶出試験第２液による試験開始１５分後の溶出率が５０％以上である経口液剤である。
