Hallucinogens are substances that produce altered sense-perceptions or states of consciousness . More specifically, they are characterized by classes of pharmacological agents which in different ways can change the subjective qualities of perception ,thought and emotion . All these classes interact with specific brain sites, often as neurotransmitter analogs or blockers, similar to many prescription drugs. The effects of hallucinogens are clearly different from stimulants like cocaine or amphetamine although they do often increase alertness or activity. The broad term “hallucinogen” is often used as a synonym for the class of psychedelics (LSD, magic mushrooms, mescaline), especially in the current scientific literature.