Hallucinogens and Psychedelics

Hallucinogens are drugs that alter perception of reality. In high-enough doses, these psychedelic or psychomimetic drugs can induce illusions, hallucinations, or delusions. The hallucinogenic state is characterized by heightened awareness of sensory input, a sense of a divided self, and feelings not experienced outside of dreams or religious experiences. Most hallucinogens are plant alkaloids and function as 5-HT2A receptor agonists. Hallucinogens can be divided into indolylalkylamines and phenylalkylamines. This chapter encompasses the history, synthesis, drug abuse patterns, pharmacology, metabolism, detection and analysis, and toxicological interpretation of classic hallucinogenic compounds, including phencyclidine (PCP), lysergic acid diethylamide (LSD), mescaline, psilocybin, and ketamine. More recently, synthetic analogs have also emerged in the illicit drug market as novel psychoactive substances, including analogs of PCP, mescaline (2C and NBOMe types), and ketamine. While PCP may be considered a dissociative anesthetic and ketamine is used as another anesthetic, they are abused for their hallucinogenic properties and are therefore discussed in detail in this chapter.