12.5: CNS Stimulants: Psychedelic Agents

Hallucinogens, also known as psychedelic drugs, are a class of substances known for their ability to alter perception, cognition, and emotions. Despite their profound effects on the mind, these drugs are non-addictive, setting them apart from many other abused substances. The mechanism of action of these drugs lies in their impact on the 5-HT_2A receptor in the brain. Upon activation, this receptor couples to G_q-type G proteins, triggering a cascade that releases intracellular calcium. This biochemical process is believed to underlie the unique psychological effects of hallucinogens. Psychedelic drugs can be divided into two main classes based on their chemical structure: indoleamines and phenethylamines. Indoleamine hallucinogens include LSD (lysergic acid diethylamide) and psilocybin, found in magic mushrooms. These drugs are known for producing vivid visual effects and a profoundly altered state of consciousness. However, they also have a downside - regular use can lead to rapid tolerance, requiring higher doses to achieve the same effects. While physical dependence is not typical, withdrawal symptoms can occur in some users. In severe cases, pharmacological intervention with drugs like diazepam may be necessary.

On the other hand, phenethylamines include substances like MDMA (3,4-Methylenedioxymethamphetamine), commonly known as ecstasy or molly, and PCP (Phencyclidine). MDMA is unique because it provides both stimulant and psychedelic effects, often eliciting feelings of empathy, euphoria, and heightened sensory perception. PCP, initially developed as an anesthetic, can cause emotional withdrawal and aggressive behavior at high doses. Like indoleamines, tolerance to phenethylamines can develop quickly, and medical intervention may be required in cases of overdose.

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.