Hallucinogen, the active principle in the flowering heads of the peyote cactus. An alkaloid related to epinephrine and norepinephrine and first isolated in 1896, mescaline is usually extracted from the peyote and purified, but can also be synthesized. When it is taken as a drug, its hallucinogenic effects begin in two to three hours and may last over 12 hours; the hallucinations vary greatly among individuals and from one time to the next, but they are usually visual rather than auditory. Side effects include nausea and vomiting.

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