Deliriant

Deliriants represent one of the most challenging and least recreational classes of psychoactive substances. Acting primarily through anticholinergic or antihistaminergic mechanisms, they produce a unique form of altered consciousness characterized by true hallucinations, hallucinations that are indistinguishable from reality, and a global confusion that prevents the user from recognizing that they are under the influence of a drug.

The general deliriant experience involves seeing and interacting with people, objects, and entities that do not exist, with complete conviction that they are real. Conversations with phantom visitors, attempts to use imaginary objects, and confusion about location and time are characteristic. Physical effects include extreme dry mouth, blurred vision, urinary retention, elevated heart rate, and dangerous hyperthermia. The experience is almost universally described as unpleasant and frightening, with lingering dysphoria that can persist for days. The class has minimal recreational appeal but significant toxicological and psychological risk.

The altered state of consciousness produced by common or 'classical' deliriant substances such as scopolamine, atropine and diphenhydramine is mediated through the drug compounds' competitive antagonism of the peripheral and central muscarinic acetylcholine receptors, especially the M1 muscarinic receptor. M1 receptors are located primarily in the central nervous system and are involved in perception, attention, and cognitive functioning.

Delirium is primarily associated with antagonism of postsynaptic M1 receptors. However, antagonism of both the M1 receptor and the M2 receptor have been implicated as having negative effects on memory and cognition, and the selective M2 receptor antagonist hyoscyamine has been reported to produce deliriant effects similarly to M1 receptor antagonists. Conversely, the M3 receptor has not been implicated in cognition.

The central nervous system actions of deliriants are complex, and other muscarinic acetylcholine receptors, including the M3, M4, and M5 receptors, may also be involved in the effects of the drugs. As an example, the M1, M2, M4 and M5 receptors have all been implicated in regulating dopamine release, with the M1, M2, and M4 receptors having inhibitory effects on dopamine release and the M5 receptor having stimulatory effects.

Peripheral muscarinic receptors are part of the autonomic nervous system. M2 receptors are located in the brain and heart, M3 receptors are in salivary glands and M4 receptors are in the brain and lungs. Scopolamine is a nonspecific muscarinic antagonist at all four (M1, M2, M3, and M4) receptor sites. Due to these compounds' inhibition of various signal transduction pathways, the decrease in acetylcholine signaling is what leads to many of the cognitive deficits and mental impairments.

It has also been said that common anticholinergic agents/hallucinogens should be more accurately referred to as antimuscarinics, as for instance these agents do not generally block nicotinic receptors.

Deliriant belongs to the deliriant class of substances, which produce a characteristic state of delirium involving true hallucinations, confusion, and amnesia. Many deliriants have been known to human cultures for millennia.

Plants containing anticholinergic alkaloids (atropine, scopolamine, hyoscyamine) — including Datura, Atropa belladonna, and Hyoscyamus niger — feature prominently in the folklore and traditional pharmacopoeia of cultures worldwide. Historical uses have included medicine, ritual, divination, and poison.

In modern pharmacology, anticholinergic compounds remain important in medicine (atropine for bradycardia, scopolamine for motion sickness), but recreational use is widely regarded as dangerous and dysphoric by the vast majority of users. The unpredictable dose-response relationship, high toxicity potential, and distressing nature of anticholinergic delirium make these among the most hazardous recreational substances.