Modern interest in hallucinogenic drugs dates from Albert Hofman's 1943 discovery of the properties of lysergic acid diethylamide (LSD) through inadvertent ingestion.1
The popularity of hallucinogens as recreational drugs peaked in the 1960s, and is currently undergoing a resurgence among adolescents and young adults. 2 In the United States in 1995, 8.4 percent of high school seniors, and 6.8 percent of college students used LSD. 2 In the same year, marijuana was used by 34.7 percent of high school seniors and 31.2 percent of college students.2 Of particular concern is the current popularity of the psychoactive amphetamine-derivative MDMA ("ecstasy" or "Adam") among college students.3 Encouragingly, the incidence of emergency department (ED) visits due to phencyclidine (PCP) has decreased sharply in the past decade.4 In 1995, annual prevalence of PCP use among high school seniors was 1.8 percent, and among young adults was only 0.3 percent. 2
Terms such as "psychedelic" are sometimes preferred to "hallucinogen." Many of the drugs within this group rarely produce true hallucinations, which are sensory perceptions occurring in the absence of any external stimulus. Perceptual alterations based on some environmental cue are termed illusions, and are far more common. These effects may involve any sensory modality, but are most often visual. Users may also experience distortions of body image, and a distorted sensation of the passage of time. Alterations in mood and heightened suggestibility are common.
The "classical" hallucinogens include agents from the indole alkylamine (LSD, psilocybin), and phenylethylamine (mescaline and others) chemical families ( Table
163-1). These drugs share a common proposed mechanism of action, and are capable of producing the profound psychological effects and sensory distortions characteristic of the psychedelic "trip." In addition to classical hallucinogens, a number of other drugs, such as MDMA ("ecstasy"), phencyclidine (PCP), and marijuana, possess the ability to alter sensory perceptions, and can be placed within the broader category of hallucinogens.
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