PROBLEM TO BE SOLVED: To provide agent for prevention or treatment of acute-phase pain in herpes zoster-related pain.SOLUTION: The present invention provides the use of a P2Xreceptor antagonist such as a diazepine dione derivative represented by the following formula (Xb).SELECTED DRAWING: None【課題】帯状疱疹関連痛の急性期疼痛の予防又は治療剤の提供。【解決手段】下記式(Xb)を代表例とするジアゼピンジオン誘導体等のP2X4受容体拮抗剤の使用。【選択図】なし