Hallucinogen
A diverse class of drugs inducing altered perception and mood.
Hallucinogens, also known as psychedelics, entheogens, or historically as psychotomimetics, are a broad and diverse class of psychoactive drugs that can induce altered states of consciousness characterized by marked changes in perception, mood, cognition, and self-experience, along with a range of other psychological alterations. They are often categorized as either psychedelics, dissociatives, or deliriants, but not all hallucinogens fall into these three classes.
- types
- Psychedelics, dissociatives, deliriants, κ-opioid receptor agonists, GABAA receptor agonists, oneirogens, others
- examples
- LSD, psilocybin, mescaline, DMT, ketamine, PCP, DXM, nitrous oxide, scopolamine, diphenhydramine, salvinorin A, ibogaine
- classification_criteria
- Hollister's five criteria; Glennon's two additional criteria for classical hallucinogens
- common_mechanisms
- 5-HT2A receptor agonism, NMDA receptor antagonism, antimuscarinic activity, κ-opioid receptor agonism, GABAA receptor agonism
Lore & Background
Hallucinogens are a broad class of psychoactive drugs that induce altered states of consciousness, with changes in perception, mood, cognition, and self-experience. They are often categorized as psychedelics (5-HT2A receptor agonists), dissociatives (NMDA receptor antagonists), or deliriants (antimuscarinics), though some, like salvinorin A and ibogaine, do not fit these categories. Leo Hollister gave five criteria for classifying a drug as hallucinogenic, including that changes in thought, perception, and mood should predominate, and addictive craving should be absent. Richard Glennon added two criteria for classical hallucinogens: binding at 5-HT2 serotonin receptors and recognition by animals trained to discriminate the drug DOM.
Reader's Guide
Hallucinogens have been described by many names, including phantastica, psychotomimetic, psychedelic, and entheogen. The term hallucinogen is the most common in scientific literature, though some argue it misleadingly emphasizes hallucinogenic properties. Psychedelics, or classical hallucinogens, are serotonin 5-HT2A receptor agonists and often produce visual alterations, including geometric patterns, and can trigger mystical experiences as measured by psychometric scales. Different classes have different mechanisms and effects: dissociatives act on NMDA receptors, deliriants on muscarinic receptors, and others on κ-opioid or GABAA receptors. Efforts to create standardized terminology for classifying hallucinogens based on subjective effects have not succeeded. Designer drugs, such as those in the 2C and 25-NB families, are structural or functional analogs designed to mimic pharmacological effects while avoiding legal classification.
Did You Know?
- Hallucinogens are often categorized as psychedelics, dissociatives, or deliriants, but not all fall into these three classes.
- Leo Hollister gave five criteria for classifying a drug as hallucinogenic, including minimal intellectual impairment and absence of addictive craving.
- Classical hallucinogens must bind at 5-HT2 serotonin receptors and be recognized by animals trained to discriminate the drug DOM.
- The term entheogen, meaning 'god within,' has seen increasing use in popular media and counterculture.
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