Diphenhydramine in the context of "Anticholinergic"

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.

A psychoactive drug, psychopharmaceutical, mind-altering drug, consciousness-altering drug, psychoactive substance, or psychotropic substance is a chemical substance that alters psychological functioning by modulating central nervous system (CNS) activity. Psychoactive and psychotropic drugs both affect the brain, with psychotropics sometimes referring to psychiatric drugs or high-abuse substances, while “drug” can have negative connotations. Novel psychoactive substances are designer drugs made to mimic illegal ones and bypass laws.

Psychoactive drug use dates back to prehistory for medicinal and consciousness-altering purposes, with evidence of widespread cultural use. Many animals intentionally consume psychoactive substances, and some traditional legends suggest animals first introduced humans to their use. Psychoactive substances are used across cultures for purposes ranging from medicinal and therapeutic treatment of mental disorders and pain, to performance enhancement. Their effects are influenced by the drug itself, the environment, and individual factors. Psychoactive drugs are categorized by their pharmacological effects into types such as anxiolytics (reduce anxiety), empathogen–entactogens (enhance empathy), stimulants (increase CNS activity), depressants (decrease CNS activity), and hallucinogens (alter perception and emotions). Psychoactive drugs are administered through various routes—including oral ingestion, injection, rectal use, and inhalation—with the method and efficiency differing by drug.

Premedication is using medication before some other therapy (usually surgery or chemotherapy) to prepare for that forthcoming therapy. Typical examples include premedicating with a sedative or analgesic before surgery; using prophylactic (preventive) antibiotics before surgery; and using antiemetics or antihistamines before chemotherapy.

Premedication before chemotherapy for cancer often consists of drug regimens (usually 2 or more drugs, e.g. dexamethasone, diphenhydramine and omeprazole) given to a patient minutes to hours before the chemotherapy to avert side effects or hypersensitivity reactions (i.e. allergic reactions).

Delirium (formerly acute confusional state, an ambiguous term that is now discouraged) is a specific state of acute confusion attributable to the direct physiological consequence of a medical condition, effects of a psychoactive substance, or multiple causes, which usually develops over the course of hours to days. As a syndrome, delirium presents with disturbances in attention, awareness, and higher-order cognition. People with delirium may experience other neuropsychiatric disturbances including changes in psychomotor activity (e.g., hyperactive, hypoactive, or mixed level of activity), disrupted sleep-wake cycle, emotional disturbances, disturbances of consciousness, or altered state of consciousness, as well as perceptual disturbances (e.g., hallucinations and delusions), although these features are not required for diagnosis.

Diagnostically, delirium encompasses both the syndrome of acute confusion and its underlying organic process known as an acute encephalopathy. The cause of delirium may be either a disease process inside the brain or a process outside the brain that nonetheless affects the brain. Delirium may be the result of an underlying medical condition (e.g., infection or hypoxia), side effect of a medication such as diphenhydramine, promethazine, and dicyclomine, substance intoxication (e.g., opioids or hallucinogenic deliriants), substance withdrawal (e.g., alcohol or sedatives), or from multiple factors affecting one's overall health (e.g., malnutrition, pain, etc.). In contrast, the emotional and behavioral features due to primary psychiatric disorders (e.g., as in schizophrenia, bipolar disorder) do not meet the diagnostic criteria for 'delirium'.

Methaqualone is a sedative-hypnotic medication that was widely prescribed during the mid-20th century. It was marketed under various brand names, including Quaalude (/ˈkweɪluːd/ KWAY-lood) and Sopor, typically containing 300 mg of methaqualone per tablet. A combination drug known as Mandrax was sold primarily in Europe, containing 250 mg of methaqualone and 20 mg of diphenhydramine in a single tablet.

Methaqualone belongs to the quinazolinone class of compounds. Its commercial production was discontinued in many countries during the mid-1980s due to widespread misuse, addiction, and associated public health concerns.