Dissociative in the context of Respiratory depression

Hallucinogens, also known as psychedelics, entheogens, or historically as psychotomimetics, are a large and diverse class of psychoactive drugs that can produce altered states of consciousness characterized by major alterations in thought, mood, and perception as well as other changes. Hallucinogens are often categorized as either being psychedelics, dissociatives, or deliriants, but not all hallucinogens fall into these three classes.

Examples of hallucinogens include psychedelics or serotonin 5-HT_2A receptor agonists like LSD, psilocybin, mescaline, and DMT; dissociatives or NMDA receptor antagonists like ketamine, PCP, DXM, and nitrous oxide; deliriants or antimuscarinics like scopolamine and diphenhydramine; cannabinoids or cannabinoid CB₁ receptor agonists like THC, nabilone, and JWH-018; κ-opioid receptor agonists like salvinorin A and pentazocine; GABA_A receptor agonists like muscimol and gaboxadol; oneirogens like ibogaine and harmaline; and others like nutmeg, carbogen, glaucine, and hallucinogenic bolete mushrooms.

Deliriants are a subclass of hallucinogen. The term was coined in the early 1980s to distinguish these drugs from psychedelics such as LSD and dissociatives such as ketamine, due to their primary effect of causing delirium, as opposed to the more lucid and less disturbed states produced by other types of hallucinogens, where rational thought is better preserved (including the ability to distinguish hallucinations from reality). The term generally refers to anticholinergic drugs, which are substances that inhibit the function of the neurotransmitter acetylcholine.

Common examples of deliriants include plants of the genera Datura and Brugmansia, both containing scopolamine, as well as higher than recommended dosages of diphenhydramine (Benadryl). A number of plant deliriants such as that of the Solanaceae family, particularly in the Americas, have been used by some indigenous cultures to reach delirious and altered states of consciousness for traditions or rituals, such as rites of passage, divination or communicating with the ancestors. Despite their long history of use, deliriants are the least-studied class of hallucinogens in terms of their behavioral and neurological effects.

NMDA receptor antagonists are a class of drugs that work to antagonize, or inhibit the action of, the N-Methyl-D-aspartate receptor (NMDAR). They are commonly used as anesthetics for humans and animals; the state of anesthesia they induce is referred to as dissociative anesthesia.

Several synthetic opioids function additionally as NMDAR-antagonists, such as pethidine, levorphanol, methadone, dextropropoxyphene, tramadol, and ketobemidone.

Phencyclidine or phenylcyclohexyl piperidine (PCP), also known in its use as a street drug as angel dust among other names, is a dissociative anesthetic mainly used recreationally for its significant mind-altering effects. PCP may cause hallucinations, distorted perceptions of sounds, and psychotic behavior. As a recreational drug, it is typically smoked, but may be taken by mouth, snorted, or injected. It may also be mixed with cannabis or tobacco.

Adverse effects may include paranoia, addiction, and an increased risk of suicide, as well as seizures and coma in cases of overdose. Flashbacks may occur despite stopping usage. Chemically, PCP is a member of the arylcyclohexylamine class. PCP works primarily as an NMDA receptor antagonist.

Dextromethorphan, sold under the brand name Robitussin among others, is a cough suppressant used in many cough and cold medicines. In 2022, the US Food and Drug Administration (FDA) approved the combination dextromethorphan/bupropion to serve as a rapid-acting antidepressant in people with major depressive disorder.

It is in the morphinan class of medications with dissociative and stimulant properties (at lower doses). Dextromethorphan does not have a significant affinity for the mu-opioid receptor activity typical of morphinan compounds and exerts its therapeutic effects through several other receptors. In its pure form, dextromethorphan occurs as a white powder.

Salvinorin A is the main active psychotropic molecule in Salvia divinorum. Salvinorin A is considered an atypical dissociative hallucinogen.

It is structurally distinct from other naturally occurring hallucinogens (such as DMT, psilocybin, and mescaline) because it contains no nitrogen atoms; hence, it is not an alkaloid (and cannot be rendered as a salt), but rather is a terpenoid. It also differs in subjective experience, compared to other hallucinogens, and has been described as having strong dissociative effects.

Hallucinogen persisting perception disorder (HPPD) is a non-psychotic disorder in which a person experiences lasting or persistent visual hallucinations or perceptual distortions after using drugs. This includes after psychedelics, dissociatives, entactogens, tetrahydrocannabinol (THC), and SSRIs. Despite being a hallucinogen-specific disorder, the specific contributory role of psychedelic drugs is unknown.

Symptoms may include visual snow, trails and after images (palinopsia), light fractals on flat surfaces, intensified colors, altered motion perception, pareidolia, micropsia, and macropsia. Floaters and visual snow may occur in other conditions.