All three agents are classified as dissociative anesthetics; when patients are given PCP or ketamine they remain conscious but exhibit no apparent response to surgical pain. The same is also true of GHB. None of the three causes muscle relaxation. As a consequence, when any of these drugs are used as anesthetics, other anesthetic agents must be administered concurrently. In spite of the similar effects produced by these agents, they are all quite different from each other and from other hallucinogens such as LSD.