Dissociative agent (primarily analgesic and amnestic): Ketamine IV, IM, intranasal: Dissociative sedation; IV onset < 1 minute, duration 10 to 20 minutes Ketamine causes a dissociative state (trance-like mind-body dissociation) that provides analgesia, sedation, and amnesia but does not cause respiratory depression or diminish upper airway tone or protective reflexes and may be a first choice for patients at risk of aspiration.