Drugs considered hallucinogens are a diverse group of compounds (Table 14–1) including lysergic acid diethylamide (LSD), designer drugs, and many others that produce perceptual distortions (rarely complete hallucinations). Phencyclidine (PCP) and ketamine are dissociative anesthetics that produce perceptual distortions similar to hallucinogens, resulting in their being classified as hallucinogens. Designer drugs are synthetic compounds that are chemically related to stimulants, often with additions to the phenyl ring of amphetamine that cause them to have hallucinogen properties. These ring substitutions, such as are found in methylenedioxymethamphetamine (MDMA; "ecstasy"), can produce perceptual distortions.