Tropane Alkaloids

Atropine, scopolamine and hyoscyamine are esters of a bicyclic tropane skeleton and competitive muscarinic antagonists, found in Datura, belladonna and related nightshades. Cocaine shares that skeleton and is filed under Stimulants as a tropane stimulant: the ring does not decide the subject, the receptor does. The members are not interchangeable either — scopolamine crosses into the brain more readily, atropine acts more strongly on the heart.

Alkaloid content varies between species, between plants of one species, between the parts of a single plant and across a season, so a preparation made from plant material carries no reliable dose. That variability, more than the pharmacology, is what puts people in hospital. Delirium can run well beyond a day, and hyperthermia from lost sweating, tachycardia and injury sustained while disoriented are the recurring harms.