The present inventors have examined IK1 channel activators and show that benzothiophene compounds have utility for visceral pain, inflammatory pain, osteoarthritic pain, neuropathic pain, or fibromyalgia. Confirmed and completed the present invention. The compound of the present invention represented by the formula (I) has an IK1 channel activating action, and prevents and / or prevents visceral pain, inflammatory pain, osteoarthritic pain, neuropathic pain, fibromyalgia and the like. Or it can be used as a therapeutic agent. The IK1 channel activator can also be used as a prophylactic and / or therapeutic agent for inflammatory pain, osteoarthritic pain, neuropathic pain, or fibromyalgia.本発明者らは、ＩＫ１チャンネル活性化剤について検討し、ベンゾチオフェン化合物が内臓痛、炎症性疼痛、変形性関節症性疼痛、神経障害性疼痛、又は線維筋痛症に有用性を示すことを確認し、本発明を完成した。式（Ｉ）で表される本発明化合物はＩＫ１チャンネル活性化作用を有し、内臓痛、炎症性疼痛、変形性関節症性疼痛、神経障害性疼痛、又は線維筋痛症等の予防及び／又は治療薬として使用しうる。ＩＫ１チャンネル活性化剤は炎症性疼痛、変形性関節症性疼痛、神経障害性疼痛、又は線維筋痛症の予防及び／又は治療薬としても使用しうる。
