12.5 : 中枢神经兴奋剂：迷幻剂

Psychedelic drugs or hallucinogens are non-addictive substances that alter perception, cognition, and emotions.

They activate the brain's 5-HT_2A receptor, which couples to the G_q protein, generating IP₃ and ultimately leads to intracellular calcium release.

Hallucinogens are classified into two main classes based on their distinctive chemical structure.

Indoleamines include agents such as LSD and psilocybin. They induce sensory distortions, hallucinations, and altered states of consciousness.

Phenethylamines include agents such as MDMA, mescaline, and  PCP.

MDMA, known as ecstasy or molly, provides both stimulant and psychedelic effects, eliciting feelings of empathy and euphoria.

PCP —initially developed as an anesthetic— caused emotional withdrawal and aggression at high doses.

Although hallucinogens do not cause physical dependence, rapid tolerance development requires drug monitoring or medical intervention. This involves patient reassurance, administering diazepam in case of severe agitation, or life support for PCP overdose.