FENTANYL, a Road with No Return

Adda Avendaño

The illegal use of this opioid drug and its analogs brings serious consequences, ranging from violent withdrawal syndrome and immune system deterioration to overdose risk or death from respiratory depression.

You’ve reached paradise. The ocean breeze caresses your face, the warmth of the sun gently embraces you, and the sound of the waves soothes you as the sea meets the blue sky on the horizon; nothing matters, nothing hurts—it's a perfect moment… suddenly, a sharp headache, dizziness, nausea, confusion, and total darkness. You’re left stranded in the middle of nowhere, plagued by endless discomfort and longing to return to that idyllic state. Withdrawal syndrome begins the moment fentanyl leaves your brain.

Professor and researcher Eliezer Chuc Meza, from the Escuela Nacional de Ciencias Biológicas (ENCB) at the Instituto Politécnico Nacional (IPN), explains that opioids such as fentanyl are chemical compounds structurally similar to certain substances naturally produced by the human body.

He explains that, to regulate behavior according to one’s environment, a part of the human brain—common to mammals in general—specializes in releasing substances distributed throughout the central nervous system that reinforce beneficial behaviors by producing sensations of pleasure and encouraging their repetition. “This is known as the brain's reward system, which reinforces behavior—either positively, by providing pleasure, or negatively, by triggering discomfort,” he notes.

“Fentanyl causes both types of reinforcement: an immediate feeling of intense pleasure when consumed and, once its effects subside, a general discomfort that marks the beginning of withdrawal syndrome—this perpetuates its use,” emphasizes the Ph.D. in Sciences with a specialization in Physiology.

The danger of fentanyl, he explains, lies in the fact that, as a synthetic opioid, it has a powerful impact on the central nervous system. Because it binds easily to the brain’s and body’s mu-opioid receptors—involved in pain regulation, pleasure, and emotions—it triggers chemical changes that induce immediate feelings of euphoria, happiness, and pain relief. According to the researcher, the changes fentanyl causes in the brain are called neuroadaptations, through which the brain rapidly adjusts to the presence of the drug, building tolerance and requiring increasingly higher doses to achieve the same effects.

Furthermore, it causes permanent changes to neuroplasticity—the brain's ability to modify its neuronal connections in response to experiences, learning, and stimuli. Since fentanyl is an exogenous opioid—not naturally produced by the body and synthetically created in a laboratory—it has a higher affinity and stronger, longer-lasting binding to mu receptors than endogenous opioids like endorphins. As a result, discontinuing its use can lead to hyperalgesia, a condition of extreme pain sensitivity, even to stimuli that are not typically painful.

“It’s important to understand that analgesia isn’t limited to physical pain—it also affects psychological or emotional pain, which includes everything from trauma and frustration to minor and major stressors. Drugs like fentanyl shut down all of that pain,” adds the expert in neuroscience and drug design. She also notes that mu receptors are found in leukocytes, the body’s immune defense cells.

Therefore, fentanyl users not only become detached from reality, which is why they are sometimes referred to as “zombies,” but also suffer from a weakened immune system, making them more susceptible to frequent health problems.

INTERESTING FACTS

AN EASY RECIPE

The substance was synthesized by chemist and pharmacobiologist Paul Janssen in 1959, patented in 1963, and approved for legal use as an intravenous analgesic in the United States in 1968.