The most frequent acute medical emergency associated with LSD use is a panic episode (the "bad trip"), which may persist up to 24 h.A trip is a period of intoxication from a hallucinogenic drug, such as lysergic acid (LSD) or magic mushrooms (psilocybin). It is called a trip because perceptions of the world change so dramatically, it can feel as if a trip to a strange, new land is taken. Unpleasant experience of hallucinogen intoxication is known as a bad trip.Harrison 19e pg: Cocaine and Other Commonly Abused Drugs