A diverse group of drugs causing alteration of thoughts, feelings, sensations, and perceptions. They include ayahuasca (a tea made from Amazonian plants containing dimethyltryptamine [DMT], the primary mind-altering ingredient); DMT (also known as Dimitri, can also be synthesized in a lab); D-lysergic acid diethylamide (LSD, clear or white odorless material made from lysergic acid found in rye and other grain fungus); peyote (mescaline, derived from a cactus or made synthetically); and 4-phosphoryloxy-N,N-dimethyltryptamine (psilocybin, from South and North American mushrooms).

A subgroup of hallucinogens produces the added sensation of feeling out of control or disconnected from one’s body or surroundings, these include: dextromethorphan (DXM, an over-the-counter cough suppressant, when used in high doses); ketamine (a human and veterinary anesthetic); phencyclidine (PCP, cyclohexylamine derivative and dissociative anesthetic); and Salvia divinorum (salvia, a Mexican, Central, and South American plant).

Hallucinogens are used in a wide variety of ways, including smoking, snorting, and transmucosally. Except for salvia, whose effects last 30 min, onset of action is within 20 to 90 min and the duration as long as 6–12 h. Hallucinogens disrupt the neurotransmitters serotonin and glutamate.

According to the NSDUH, in 2015, an estimated 1.2 million (0.5%) of people aged ≥12 reported current hallucinogen use. The highest rates were among young adults aged 18–25, with 1.8% (636,000) young adults reporting current use.

Clinical manifestations include hallucinations, intensified feelings, heightened sensory experiences, and time perturbations. Additional physiologic responses include nausea, increased heart rate, blood pressure, respiratory rate, or body temperature, loss of appetite, xerostomia, sleep problems, synesthesia, impaired coordination, and hyperhidrosis. “Bad trips” (negative experiences with hallucinogen use) can include panic, paranoia, and psychosis, and may persist for up to 24 h. Such experiences are best treated with supportive reassurance. Some evidence that chronic effects of hallucinogen use can occur, including persistent psychosis, memory loss, anxiety, depression, and flashbacks.

No approved medications exist for treatment of hallucinogen addiction.