Effect of the Antihistamine Injection to Prevent Paradoxical Reaction During Sedative Endoscopy

This single-blind prospective study is aimed to investigate the effect of antihistamine as an adjunctive sedative for the patients with histories of severe paradoxical reaction to midazolam during sedative endoscopy. Participating patients are to receive antihistamine intravenously in addition to midazolam. The primary outcome is the reduction of paradoxical reaction in the antihistamine combination group. The secondary outcome is to compare sedation quality, performance quality, reduction of total midazolam dose will be analyzed between antihistamine combination and midazolam only group.