Hyoscyamine in the context of "Datura stramonium"

Atropa bella-donna, commonly known as deadly nightshade or belladonna, is a toxic perennial herbaceous plant in the nightshade family Solanaceae, which also includes tomatoes, potatoes and eggplant. It is native to Europe and Western Asia, including Turkey, its distribution extending from England in the west to western Ukraine and the Iranian province of Gilan in the east. It is also naturalised or introduced in some parts of Canada, North Africa and the United States.

The foliage and berries are extremely toxic when ingested, containing tropane alkaloids. It can also be harmful to handle and/or touch these plants. These toxins include atropine, scopolamine, and hyoscyamine, which cause delirium and hallucinations, and are also used as pharmaceutical anticholinergics. Tropane alkaloids are of common occurrence not only in the Old World tribes Hyoscyameae (to which the genus Atropa belongs) and Mandragoreae, but also in the New World tribe Datureae—all of which belong to the subfamily Solanoideae of the plant family Solanaceae.

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.