A deliriant is a class of drug that produces a distinctive kind of hallucination: one so vivid and realistic that the person experiencing it genuinely cannot tell it apart from reality. Unlike the geometric patterns and visual distortions caused by psychedelics, deliriant hallucinations tend to involve fully formed people, objects, and conversations that simply are not there. The pharmacological thread connecting most deliriants is their ability to block acetylcholine, a neurotransmitter critical for perception, attention, and memory. That blockade creates a toxic state resembling delirium, which is where the name comes from, and the experience is overwhelmingly described as frightening rather than insightful or pleasurable.
How Deliriants Work in the Brain
Most substances classified as deliriants are anticholinergic, meaning they interfere with the neurotransmitter acetylcholine by blocking muscarinic receptors in the brain. Acetylcholine plays a central role in how you pay attention, form memories, and distinguish real sensory input from internally generated noise. When a drug blocks these receptors, particularly the M1 subtype responsible for perception and cognition, the brain’s ability to filter and verify sensory information breaks down. The result is a state that clinicians recognize as anticholinergic delirium: confusion, agitation, pressured and often incomprehensible speech, and hallucinations that are typically visual but can involve any sense.1PubMed Central. Delirium secondary to anticholinergics
The hallmark deliriant compounds, atropine and scopolamine, produce what researchers describe as “dream-like hallucinations” alongside characteristic hyperactivity.2ACS Chemical Neuroscience. Understanding Central Nervous System Effects of Deliriant Hallucinogenic Drugs through Experimental Animal Models “Dream-like” is an apt description because the experience shares features with dreaming: the person interacts with imaginary scenarios as if they were real and typically has little or no awareness that anything unusual is happening. Reports of picking at invisible objects, carrying on conversations with people who aren’t present, or attempting to use phantom items like cigarettes or phones are common clinical observations. One case study described a patient “feeding animals” in his hospital room, an activity that was almost certainly a visual hallucination.1PubMed Central. Delirium secondary to anticholinergics
How Deliriant Hallucinations Differ from Psychedelic Ones
People sometimes lump all hallucinogens together, but the deliriant experience is fundamentally different from what happens on a psychedelic like psilocybin or LSD. Psychedelics primarily act on serotonin receptors and tend to produce visual distortions of things that are actually there: surfaces may breathe, colors may intensify, and geometric patterns may overlay your visual field. Throughout most of this, you generally know you are under the influence of a drug. The hallucinations are more like embellishments on reality than replacements of it.
Deliriants replace reality altogether. You might see a friend sitting on your couch and have a full conversation before realizing the couch is empty. You might try to smoke a cigarette that materializes in your hand and then vanishes. The critical difference is the loss of insight: deliriant users typically do not know they are hallucinating while the experience is happening. This is what makes the class so dangerous compared to classical psychedelics. A person on a deliriant may wander into traffic or injure themselves because they are responding to a version of the world that exists only in their brain. The memory blackouts that follow compound the danger, because the person often cannot recall what they did during the episode.
Where Deliriants Come From
Deliriant compounds show up in two broad categories: naturally occurring plant alkaloids and synthetic or over-the-counter medications.
Plant Sources
The most notorious botanical deliriants belong to the nightshade family, Solanaceae. Datura stramonium (jimsonweed or thorn apple), Atropa belladonna (deadly nightshade), and Hyoscyamus niger (henbane) all produce tropane alkaloids, primarily scopolamine, atropine, and hyoscyamine, that act as potent anticholinergics.3PubMed Central. Modulation of Tropane Alkaloids’ Biosynthesis and Gene Expression by Methyl Jasmonate in Datura stramonium L. Less well-known species like Anisodus luridus, used in traditional Chinese medicine, contain the same alkaloids in even higher concentrations.4PubMed Central. Optimization of Tropane Alkaloids Extraction from Anisodus luridus Utilizing Response Surface Methodology and Quality Assessment through UPLC Fingerprinting
A major hazard with plant-derived deliriants is the wildly inconsistent potency. The alkaloid content in Datura, for instance, varies dramatically between individual plants, between different parts of the same plant, and even between seeds from the same pod. This makes dosing essentially a guess, and the margin between a dose that produces mild effects and one that causes life-threatening toxicity is very narrow. Emergency departments see Datura poisoning cases regularly, particularly among teenagers experimenting after reading about it online.
Over-the-Counter Medications
Several common medications have anticholinergic activity that can produce deliriant effects at high doses. The most frequently misused is diphenhydramine (sold as Benadryl), a first-generation antihistamine whose secondary anticholinergic properties can cause full-blown delirium when taken far above the recommended dose.5PubMed. A Qualitative Analysis of First-Hand Accounts of Diphenhydramine Misuse Available on YouTube Dimenhydrinate (Dramamine), which is partly composed of diphenhydramine, carries similar risks. These drugs are inexpensive, legal, and available without a prescription at virtually any pharmacy, which contributes to their misuse.
Physical Effects and the Anticholinergic Toxidrome
The mental effects of deliriants get the most attention, but the physical side is where the immediate danger often lies. Anticholinergic toxicity produces a recognizable cluster of symptoms that emergency physicians sometimes remember with the mnemonic “blind as a bat, dry as a bone, red as a beet, mad as a hatter, hot as a hare.” In plainer terms, these drugs cause dilated pupils and blurred vision, dry mouth and skin, flushing, confusion and agitation, and elevated body temperature. At higher doses, the picture becomes genuinely dangerous: seizures, abnormal heart rhythms, hyperthermia, and in severe cases death.6JETem (Journal of Education and Teaching in Emergency Medicine). Anticholinergic Toxicity in the Emergency Department
The cardiovascular effects deserve special emphasis. Anticholinergic drugs speed up the heart and can cause dangerous rhythm disturbances. In a case involving a 19-year-old who ingested a massive dose of dimenhydrinate, the patient presented with both status epilepticus (continuous seizures) and ventricular dysrhythmias, and death occurred within hours.7PubMed. Fatality secondary to massive overdose of dimenhydrinate Diphenhydramine overdoses similarly carry risks of seizures, abnormal heart rhythms, coma, and death.8PubMed Central. Diphenhydramine Overdose: A Case Report and Topic Review of Prehospital Diagnosis and Treatment In some cases, the intense muscular agitation caused by anticholinergic toxicity triggers rhabdomyolysis, a breakdown of skeletal muscle tissue that can lead to kidney failure.9PubMed. Rhabdomyolysis and acute renal failure following an ethanol and diphenhydramine overdose
Memory Loss and Cognitive Effects
One of the most reliable effects of deliriant compounds is amnesia. Scopolamine in particular is so effective at disrupting memory formation that researchers routinely use it in laboratory settings to induce amnesia in test animals when studying potential memory-enhancing drugs.10PubMed. Scopolamine induced amnesia is reversed by Bacopa monniera through participation of kinase-CREB pathway The amnesia works in both directions: scopolamine can prevent new memories from forming (anterograde amnesia) and impair retrieval of existing ones (retrograde amnesia).11PubMed. Anti-amnesic effect of Ficus religiosa in scopolamine-induced anterograde and retrograde amnesia
For someone who takes a deliriant recreationally, this amnesia means the experience often leaves little recoverable memory. People frequently describe “coming to” in unfamiliar places with no recollection of how they got there or what happened during the previous several hours. This combination of realistic hallucinations, loss of insight, and subsequent amnesia creates a uniquely hazardous situation. A person under the influence behaves as though awake and interacting with the world, possibly doing dangerous things, and then has no memory of any of it.
Long-Term Risks of Anticholinergic Exposure
Beyond the acute dangers of a single deliriant episode, there is growing evidence that cumulative anticholinergic exposure over time raises the risk of cognitive decline and dementia. A large prospective study following older adults over an average of about seven years found that those with the highest cumulative anticholinergic exposure had roughly a 54% greater risk of developing dementia and a 63% greater risk of Alzheimer’s disease compared to people with no anticholinergic use, with a clear dose-response pattern.12PubMed Central. Cumulative Use of Strong Anticholinergic Medications and Incident Dementia
A separate large case-control study also found an association between cumulative anticholinergic drug prescriptions and dementia risk, with the highest exposure category showing about a 49% increase in adjusted odds of dementia compared to no exposure.13JAMA Internal Medicine. Anticholinergic Drug Exposure and the Risk of Dementia: A Nested Case-Control Study A third study, this time a case-control analysis using UK primary care data, confirmed the association: prescriptions for strongly anticholinergic drugs were linked to an increased odds ratio for dementia that rose with higher average anticholinergic burden scores.14BMJ. Anticholinergic drugs and risk of dementia: case-control study
These studies examined cumulative exposure to anticholinergic medications prescribed for conditions like allergies, bladder overactivity, and depression, not recreational deliriant abuse per se. But the finding is relevant because people who misuse deliriant drugs are flooding their brains with exactly the same kind of anticholinergic activity, often at doses far exceeding anything a doctor would prescribe. Whether episodic high-dose exposure carries the same long-term risk as chronic low-dose use hasn’t been studied directly, but the underlying mechanism is the same, and the doses involved in misuse are dramatically higher.
Who Is Most Vulnerable
Older adults face disproportionate risk from anticholinergic substances. In hospitalized elderly patients, higher anticholinergic burden was associated with a three- to six-fold increased risk of delirium compared to those not taking anticholinergic drugs.15PubMed. Relation Between Delirium and Anticholinergic Drug Burden in a Cohort of Hospitalized Older Patients: An Observational Study A separate study of elderly patients during acute hospital stays confirmed a statistically significant association between anticholinergic medication use and the development of delirium.16PubMed. Anticholinergic burden and delirium in elderly patients during acute hospital admission Aging brains have less acetylcholine to spare, making them far more sensitive to drugs that block it.
Adolescents represent the other high-risk group, though for different reasons. They are more likely to experiment with readily available substances and more susceptible to peer influence and social media trends. They also tend to have less awareness of the pharmacological risks involved. The collision of easy access (any pharmacy sells diphenhydramine) with adolescent risk-taking behavior creates a persistent public health concern that has intensified in recent years.
The Benadryl Challenge and Social Media Trends
Starting around 2020, videos began circulating on TikTok and YouTube daring viewers to take large quantities of diphenhydramine and film themselves experiencing the effects. Dubbed the “Benadryl Challenge,” the trend led to a measurable surge in poison control calls and emergency department visits among teenagers. An analysis of poison center data covering 2007 through 2020 identified over 47,000 adolescent diphenhydramine ingestions, with intentional ingestions increasing over time and associated with more serious outcomes including cardiac complications, seizures, and deaths.17PubMed. A different challenge with Benadryl: adolescent diphenhydramine ingestions reported to National Poison Database System, 2007-2020
Researchers who tracked the timing of online mentions against poison center call data found that spikes in web discussion of the challenge were followed by sustained increases in adolescent-related poison center calls lasting more than 25 days after each online surge.18PubMed Central. Web Monitoring as an Early Warning System: “Benadryl Challenge” Online Mentions Correlate With Diphenhydramine Overdoses Reported to US Poison Centers The finding illustrates how quickly social media can translate online content into real-world medical emergencies. The FDA eventually issued a public warning about the trend, and some retailers began restricting the quantity of diphenhydramine that could be purchased at once.
Diagnostic Confusion in Clinical Settings
Anticholinergic delirium can be surprisingly difficult to distinguish from a genuine psychiatric emergency. The symptoms, including visual hallucinations, agitation, disorganized speech, and bizarre behavior, overlap closely with acute psychosis. This has led to documented cases where patients experiencing anticholinergic toxicity were initially treated as if they were having a psychotic break, which delays appropriate medical treatment and may expose them to additional drugs that worsen the anticholinergic burden. A published case report described the challenge of differentiating anticholinergic delirium from a first episode of psychosis in an adolescent, noting the diagnostic difficulties involved.19Journal of Clinical Studies and Medical Case Reports. Lessons from CL Psychiatry: Recognising Co-Existing Anti-Cholinergic Delirium in an Acute First Episode Psychosis Presentation in an Adolescent
The physical signs of anticholinergic toxicity, especially dilated pupils, dry flushed skin, urinary retention, and elevated heart rate, are the clinical clues that can steer diagnosis in the right direction. When these accompany psychiatric-looking symptoms, toxicology testing and a careful medication or substance history become essential.
Treatment for Anticholinergic Toxicity
The specific antidote for anticholinergic poisoning is physostigmine, a drug that temporarily increases acetylcholine levels by blocking the enzyme that normally breaks it down. Physostigmine can reverse the agitation, hallucinations, and confusion of anticholinergic delirium, and a study of its use in emergency settings found that patients treated with physostigmine alone had a significantly lower rate of intubation compared to those treated with other approaches.20PubMed Central. The Use of Physostigmine by Toxicologists in Anticholinergic Toxicity Despite this, physostigmine has historically been underused because of concerns about side effects, particularly in patients who have also taken drugs that affect cardiac conduction. In practice, when the diagnosis is clearly anticholinergic toxicity, the evidence supports physostigmine as relatively safe and effective.
Supportive care remains the backbone of treatment. Cooling measures for hyperthermia, benzodiazepines for seizures and severe agitation, cardiac monitoring, and intravenous fluids are standard. In severe diphenhydramine overdoses, sodium bicarbonate may be used if the heart’s electrical conduction is dangerously slowed. The key first step, though, is recognizing the toxidrome for what it is rather than attributing the symptoms to a psychiatric condition.
Historical Use of Deliriant Plants
Humans have been using deliriant-containing plants for centuries, and not always accidentally. Henbane (Hyoscyamus niger) was known to ancient civilizations both as a poison and as a narcotic, and it was widely used by practitioners of folk medicine and occult ritual as a component of hallucinatory preparations.21Journal of the Royal College of Physicians of Edinburgh. Solanaceae III: henbane, hags and Hawley Harvey Crippen The most famous application was in the so-called “flying ointments” of early modern Europe, salves applied to the skin that were said to enable witches to fly. Scholarly analysis suggests these ointments had an actual basis in historical fact: they contained tropane alkaloids from henbane, mandrake, and belladonna, and absorption through the skin or mucous membranes could produce vivid hallucinations of flying and other extraordinary experiences.22Journal of Psychedelic Studies. Those Goddamn ointments: Four histories
The connection between anticholinergic plants and the sensation of flight makes pharmacological sense. Deliriants produce such convincing hallucinations that a person rubbing a tropane-laced ointment on their body could genuinely believe they had left the ground. Combined with the amnesia that follows, the person would awake with fragmented, dreamlike memories of impossible events, experiences that could easily be interpreted through the supernatural framework of the era.
Scopolamine as a Criminal Tool
Scopolamine’s ability to produce confusion, suggestibility, and amnesia has made it a tool for drug-facilitated crime. Reports from South America and Europe describe victims being surreptitiously dosed with scopolamine and then robbed or sexually assaulted while in a compliant, amnestic state. Forensic researchers have documented both fatal and non-fatal scopolamine-facilitated robberies, noting that blood concentrations and doses used in such crimes are often poorly understood because the drug is metabolized quickly.23Forensic Science International. Toxicological results in a fatal and two non-fatal cases of scopolamine-facilitated robberies
Detection is a significant challenge. Scopolamine’s high potency means only a tiny amount is needed to incapacitate someone, and the drug is cleared from blood and urine rapidly. When victims report the crime days later, standard blood and urine tests may no longer detect the drug. Hair analysis can extend the detection window considerably and has been proposed as an essential supplemental tool in cases of drug-facilitated sexual assault where the victim delays reporting.24PubMed. Detection of scopolamine in urine and hair in a drug-facilitated sexual assault
Why These Plants Make Deliriant Compounds at All
From the plant’s perspective, tropane alkaloids are a defense system. Research on Datura stramonium has directly examined natural selection acting on its alkaloids and found evidence that insect herbivores drive the evolution of these chemical defenses. The study found that both scopolamine and hyoscyamine were under active selection pressure, with natural selection acting to reduce scopolamine levels while maintaining an intermediate level of hyoscyamine, suggesting the alkaloid balance reflects an ongoing evolutionary negotiation between the costs of producing chemical defenses and the benefits of deterring insects.25PubMed. Evolutionary ecology of the tropane alkaloids of Datura stramonium L. (Solanaceae)
The same anticholinergic activity that scrambles a human brain also disrupts insect nervous systems, which rely on similar acetylcholine signaling. It’s a reminder that these compounds did not evolve for human consumption. They are chemical weapons in a war between plants and the creatures that eat them. The fact that they happen to produce vivid, terrifying hallucinations in humans is an incidental consequence of shared neurotransmitter biology across the animal kingdom.
Atypical Deliriants
Not every substance that can produce delirium-like states works through the classic anticholinergic pathway. Nutmeg, a common kitchen spice, contains myristicin, which acts on serotonin receptors and in large quantities can produce hallucinations, confusion, and other psychomimetic symptoms.26PubMed. Stoned on spices: a mini-review of three commonly abused household spices The experience is generally described as deeply unpleasant, with nausea, a pounding headache, and a paranoid, confused mental state that can last over 24 hours. Nutmeg intoxication is rare precisely because the experience is so miserable that few people try it twice.
Some synthetic research chemicals have also been described as having deliriant properties, though these are less well-studied and less commonly encountered. The important point is that while the anticholinergic mechanism accounts for most classical deliriant experiences, the state of realistic hallucinations combined with lost insight can occasionally be produced through other pharmacological routes. What these substances share is not a single receptor target but an end result: the brain’s reality-testing apparatus fails in a way that leaves the person unable to recognize that what they are seeing and hearing is not real.