Fentanyl: Definition, Uses, and Side Effects

Fentanyl is a highly potent synthetic opioid used for pain management and has also become a major factor in the opioid crisis in the U.S. It is 50 to 100 times stronger than morphine, and its illicit use has led to thousands of overdose deaths annually. In 2023, DEA seized more than 80 million fentanyl-laced fake pills and nearly 12,000 pounds of fentanyl powder. The 2023 seizures are equivalent to more than 390 million lethal doses of fentanyl. The 2024 fentanyl seizures represent over 367 million deadly doses with 2 mg of fentanyl equates to a potentially deadly dose.

Medically, fentanyl is prescribed for severe pain, such as cancer pain, post-surgical pain, and palliative care. It is available in various forms, including patches, injections, and lozenges, allowing controlled administration. Due to its rapid onset and high potency, it is commonly used in hospitals for anesthesia and pain relief in acute care settings.

The side effects of fentanyl include respiratory depression, confusion, dizziness, nausea, sedation, and pinpoint pupils, according to a study by Healthdirect in “Fentanyl – about, use, side effects and alternatives.” The most dangerous effect is its ability to slow or stop breathing, increasing the risk of fatal overdose, mainly when mixed with other substances like heroin or counterfeit pills.

Fentanyl is highly addictive due to its powerful effect on the brain’s opioid receptors, triggering intense euphoria and dopamine release. This creates a strong cycle of dependence, leading to tolerance and withdrawal symptoms. Its extreme potency makes addiction even more dangerous, as users unknowingly consume a lethal dose with just a small amount.

What is Fentanyl?

Fentanyl is a potent synthetic opioid, approximately 100 times more powerful than morphine, initially synthesized in 1959 and introduced in the 1960s as an intravenous anesthetic. According to the Drug Fact Sheet by the Drug Enforcement Administration (DEA), “Fentanyl is a potent synthetic opioid drug approved by the Food and Drug Administration for use as an analgesic (pain relief) and anesthetic. It is approximately 100 times more potent than morphine and 50 times more potent than heroin as an analgesic.” 

Medically, Fentanyl is utilized for managing severe pain, particularly post-surgical pain and in advanced-stage cancer patients, as studied by the National Institute for Drug Abuse (NIDA). Beyond its legitimate pharmaceutical applications, fentanyl has permeated the illicit drug market. Illicitly manufactured fentanyl is mixed with other drugs, such as methamphetamine, heroin, and cocaine, exacerbating the risk of overdose and associated fatalities.

In the United States, fentanyl has significantly contributed to the opioid crisis. Overdose deaths involving synthetic opioids, primarily fentanyl, have surged from around 3,000 in 2013 to more than 30,000 in 2018, according to a report by Rand titled “Fentanyl: The Most Dangerous Illegal Drug in America.” Law enforcement seizures of illicit fentanyl have also increased dramatically, with over 115 million pills containing fentanyl seized in 2023, compared to 49,657 in 2017, as reported by the  National Institute for Drug Abuse (NIDA). 

What are the Street Names of Fentanyl?

The street names of fentanyl are Apace, China Girl, and Dance Fever, among others. These names emerge from cultural references, the drug’s effects, or its origin. Many of these aliases stem from fentanyl’s potency, its association with China as a primary source of production, or its euphoric yet dangerous properties.

The street names of fentanyl are as follows:

• Apace: A term suggesting the rapid and intense effects of fentanyl.
• China Girl:  Derived from China’s historical role in fentanyl supply and a reference to David Bowie’s song.
• China Town: Related to fentanyl’s trafficking routes and distribution hubs.
• Dance Fever: Alludes to the uncontrollable movements or convulsions caused by fentanyl overdose.
• Friend: A misleading name suggesting a false sense of comfort or euphoria.
• Goodfellas: Inspired by the famous mobster film, possibly indicating its presence in the illegal trade.
• Great Bear: Possibly signifies the overwhelming potency of fentanyl, resembling a bear’s strength.
• He-Man: Suggests the false perception of strength and invincibility fentanyl provide.
• Jackpot: Implies the extreme high users seek, though with deadly consequences.
• King Ivory: References fentanyl’s powdered white form, resembling ivory.
• Murder 8: A grim nod to fentanyl’s lethal potential, “8” could reference its strength compared to morphine.
• Poison: A direct reference to its deadly nature and frequent overdose cases.
• Tango & Cash: Named after the 1989 crime film, possibly indicating its high value in the black market.

How Does Fentanyl Work? 

Fentanyl works by binding to mu-opioid receptors in the brain and spinal cord, which are responsible for regulating pain and emotions. As a synthetic opioid, it mimics the body’s natural endorphins but with significantly greater potency. When fentanyl attaches to these receptors, it inhibits pain signals, providing intense analgesia and a sense of euphoria. This mechanism also slows breathing and heart rate, increasing the risk of respiratory depression and overdose, as studied by Ramos-Matos CF, Bistas KG, Lopez-Ojeda W. et al. 2023, titled “Fentanyl.”

Once administered, fentanyl acts rapidly, within seconds to minutes, depending on the form: intravenous, transdermal, or oral. It has a high lipid solubility, allowing it to cross the blood-brain barrier quickly, making it one of the fastest-acting opioids. In the central nervous system, fentanyl depresses nerve activity, leading to sedation, relaxation, and, in high doses, unconsciousness. Its potency and rapid onset make it valuable in medical settings for pain management but also highly dangerous when misused, as even a tiny amount is fatal.

How is Fentanyl Consumed?

Fentanyl is consumed in various forms, including snorting, smoking, oral ingestion through pills or tablets, and transdermal patches, each differing in potency, onset, and risk. It is snorted or sniffed, inhaling the powder through the nose, rapidly entering the bloodstream, and producing an almost immediate high. Smoking fentanyl involves heating the powder or residue on foil and inhaling the vapors, leading to fast absorption through the lungs.

Orally, fentanyl is available in pills, tablets, and lozenges when prescribed, but illicit versions are counterfeit, designed to mimic oxycodone, Xanax, or other pharmaceutical opioids. These fake pills frequently contain lethal doses of fentanyl, posing a significant overdose risk. It is also spiked onto blotter paper, similar to LSD, allowing it to be absorbed through the mucous membranes of the mouth.

In medical settings, fentanyl patches are used for long-term pain relief, gradually releasing the drug through the skin. However, illicit users extract the gel from patches and inject or ingest it for a more immediate effect. Fentanyl is sometimes mixed with heroin, cocaine, or methamphetamine, sometimes unknowingly, leading to unexpected and deadly overdoses. Because fentanyl is so potent, even tiny, unmeasured doses in illicit forms are fatal, making its consumption extremely dangerous outside of controlled medical use.

What are the Medical Uses of Fentanyl? 

The medical uses of fentanyl are primarily for pain management, anesthesia, and palliative care, where it is administered in strictly controlled medical settings. Due to its potency and rapid onset, fentanyl is used to manage severe pain, particularly in post-surgical recovery, cancer treatment, and end-of-life care. It is also a key component in surgery anesthesia, where precise dosage regulation is necessary to ensure patient safety. In cases of regional anesthesia and obstetric procedures, fentanyl is sometimes combined with other anesthetics to enhance pain relief while minimizing side effects. Given its high potency, medical use of fentanyl requires careful dosage control to prevent complications such as respiratory depression.

The medical uses of fentanyl are as follows: 

Anesthesia

Fentanyl is widely used as part of general anesthesia due to its powerful analgesic effects and ability to induce sedation quickly, as addressed by Smith G, D’Cruz JR, Rondeau B, et al. 2023, in their study titled “General Anesthesia for Surgeons.” It is combined with other anesthetic agents to provide a balanced anesthetic state, reducing the need for high doses of other drugs that might have more severe side effects. Its use in anesthesia ensures that patients remain pain-free during major surgical procedures while also stabilizing heart rate and blood pressure.

Regional Anesthesia

In regional anesthesia, fentanyl is administered through epidural or spinal injections to enhance pain relief without the need for full sedation. It is commonly used in procedures involving the lower body or limbs, where localized pain relief is needed while keeping the patient conscious. The addition of fentanyl helps prolong and intensify the anesthetic effect, reducing the amount of local anesthetic required and minimizing post-procedure discomfort.

Obstetrics

Fentanyl is frequently used in labor and delivery, particularly in epidural analgesia for women undergoing childbirth. It provides effective pain relief while allowing the mother to remain alert and active during labor, as studied by Douglas J, Peter E, Preston R, Swenerton J, Campbell K., et al. 2010, in “Obstetric Guideline 4: Pain Management Options During Labour. In: Obstetric Guidelines.” Compared to traditional opioid medications, fentanyl has a faster onset, shorter duration, and lower risk of affecting the newborn, making it a preferred choice in obstetric pain management.

Pain Management

Fentanyl is a necessary option for managing severe and chronic pain, particularly for cancer patients, post-operative recovery, and palliative care. It is available in various forms, including transdermal patches, intravenous infusions, and lozenges, allowing for continuous and controlled pain relief in 77% of cancer patients, as studied by Hadley G, Derry S, Moore RA, Wiffen PJ. et al. 2013, in “Transdermal fentanyl for cancer pain.” In end-of-life care, fentanyl helps alleviate suffering in terminal patients, providing comfort without excessive sedation. Due to its potency, medical professionals carefully regulate its dosage to prevent overdose and respiratory complications.

What are the Side Effects of Fentanyl? 

The side effects of fentanyl are respiratory problems, high overdose risk, and potential for addiction. As a potent opioid, fentanyl depresses the central nervous system, leading to dangerous respiratory effects, cognitive impairment, and a high potential for dependence. Careful monitoring is required to prevent severe complications even in controlled medical use.

The side effects of fentanyl are listed below:

• Respiratory Problems: Fentanyl significantly suppresses the respiratory centers in the brainstem, reducing the body’s ability to detect rising carbon dioxide levels. This leads to hypoventilation, respiratory distress, and oxygen deprivation, ultimately resulting in respiratory failure, a leading cause of fentanyl-related fatalities, as studied by Topacoglu H, Karcioglu O, Cimrin AH, Arnold J., et al. 2005, in a case study of a 31-year-old man titled “Respiratory arrest after low-dose fentanyl.” This is a physical side effect directly affecting lung function and oxygen intake.
• High Overdose Risk: Due to the high potency of fentanyl, 50 to 100 times stronger than morphine, even small amounts of fentanyl lead to overdose. Symptoms include unresponsiveness, slowed breathing, cyanosis (bluish skin), and cardiac arrest. Research has found that fentanyl overdoses account for over 70% of synthetic opioid-related deaths in the U.S. This physical side effect leads to severe bodily harm or death, as studied by the Centers for Disease Control and Prevention, 2023, in a study titled “Synthetic Opioids and Overdose Trends in the United States.”
• Potential for Addiction: Fentanyl activates the brain’s reward system, releasing excessive dopamine and creating strong euphoric effects. This leads to rapid dependence and addiction, even after short-term use. A study by Nature suggests fentanyl has a higher abuse potential than other opioids due to its fast onset and powerful reinforcement properties. This behavioral and psychological side effect of fentanyl alters mood, cravings, and compulsive drug-seeking behavior, according to a study by  Alzu’bi A. et al. 2024, titled “The impact of chronic fentanyl administration on the cerebral cortex in mice: Molecular and histological effects.”
• Shallow Breathing: Shallow breathing is a direct consequence of fentanyl’s respiratory depression. It occurs when the body fails to take in enough oxygen, leading to hypoxia and potential brain damage. This physical side effect of fentanyl results in unconsciousness or death, as studied by Solis E Jr, Cameron-Burr KT, Shaham Y, and Kiyatkin EA. et al. 2018, titled “Fentanyl-Induced Brain Hypoxia Triggers Brain Hyperglycemia and Biphasic Changes in Brain Temperature.”
• Confusion: Confusion is a psychological side effect of fentanyl as it affects the brain’s ability to process information. Fentanyl impairs cognitive function by depressing neuronal activity in the prefrontal cortex, affecting decision-making, memory, and coordination. This increases the risk of accidents and overdose due to impaired judgment. According to a study by Tamargo JA MS et al. 2021, in “Cognitive Impairment among People Who Use Heroin and Fentanyl: Findings from the Miami Adult Studies on HIV (MASH) Cohort,” cognitive impairment was more frequent among people who used heroin and/or fentanyl than those who misused prescription opioids, 31.6% vs. 10.5%.
• Drowsiness: Drowsiness is a common physical side effect of fentanyl. It occurs due to central nervous system depression, which reduces alertness and reaction time. Prolonged use of fentanyl contributes to sedation-related accidents and falls and directly affects body function.
• Dizziness: Fentanyl lowers blood pressure (hypotension) and impairs the inner ear’s balance system, causing dizziness and lightheadedness. This increases the risk of fainting and injury. Dizziness is a physical side effect due to its impact on the circulatory and vestibular systems, as studied by Chimirri S et al. 2013, in “Vertigo/dizziness as a Drugs’ adverse reaction.”
• Nausea & Vomiting: Opioids like fentanyl trigger the chemoreceptor trigger zone (CTZ) in the brainstem, leading to severe nausea and vomiting. This physical side effect of fentanyl affects the digestive system, according to a study by the Alcohol and Drug Foundation.
• Pinpoint Pupils: Pinpoint pupils, also known as miosis, are a physical side effect caused by the constant use of fentanyl. Fentanyl constricts the pupils by stimulating the Edinger-Westphal nucleus in the midbrain. 
• Risk of Coma: In high doses, fentanyl induces deep sedation, respiratory arrest, and loss of consciousness, leading to opioid-induced coma. This physical side effect of fentanyl results from direct opioid toxicity in the brain, as studied by Pfizer in “Serious And Life-Threatening Risks From Use ‎of Fentanyl ‎citrate Injection.”
• Constipation: Fentanyl binds to mu-opioid receptors in the gastrointestinal tract, reducing peristalsis and causing severe constipation. Long-term opioid use leads to opioid-induced bowel dysfunction (OIBD), a serious and painful physical side effect of fentanyl impacting the digestive system. According to a study by Müller-Lissner S et al. 2017, titled “Opioid-Induced Constipation and Bowel Dysfunction: A Clinical Guideline,” in a nonrandomized, retrospective study, the rates of constipation were 3.7% for transdermal fentanyl.

Is Fentanyl Addictive?

Yes, fentanyl is highly addictive. As a potent synthetic opioid, it binds to mu-opioid receptors in the brain, triggering a rapid and intense release of dopamine, which reinforces drug-seeking behavior and dependence. Its high potency and fast-acting nature make it even more addictive than many other opioids, increasing the risk of both physical dependence and psychological addiction. 

Over time, users develop tolerance, requiring higher doses to achieve the same effects, which significantly raises the risk of overdose. Fentanyl addiction leads to severe withdrawal symptoms, including muscle pain, insomnia, nausea, and intense cravings, making it difficult to quit without medical intervention.

What Makes Fentanyl So Addictive?

Fentanyl is so addictive because of its potent ability to bind to opioid receptors in the brain, triggering the release of high levels of dopamine, a neurotransmitter associated with pleasure and reward. When fentanyl binds to the mu-opioid receptors, it induces a rapid and intense feeling of euphoria, which reinforces the desire to seek out the drug again. 

The overwhelming rush of dopamine created by fentanyl use initiates a powerful reward system feedback loop, leading users to repeatedly use the drug to experience the same feelings of pleasure. As fentanyl is 50 to 100 times more potent than morphine, its ability to produce such intense effects in a short time further amplifies its addictive potential. 

Repeated use of fentanyl leads to tolerance, where higher doses are needed to achieve the same effect, increasing both dependency and the risk of overdose. Research by Comer SD, Cahill CM. et al. 2019, in their findings titled “Fentanyl: Receptor pharmacology, abuse potential, and implications for treatment,” have demonstrated that fentanyl’s rapid onset and high abuse potential are key factors in its ability to cause addiction and physical dependence.

Does Fentanyl Have Withdrawal Symptoms?

Yes, fentanyl has withdrawal symptoms. When someone dependent on fentanyl stops using it suddenly or reduces their dose, they experience a range of withdrawal symptoms due to the body’s adaptation to the drug. These symptoms are both physical and psychological and vary in severity depending on the individual’s level of dependence. Withdrawal occurs because the brain’s dopamine system has become reliant on the drug to function properly, and without fentanyl, the system becomes imbalanced. 

Common fentanyl withdrawal symptoms include:

• Muscle pain
• Insomnia
• Nausea
• Vomiting
• Sweating
• Anxiety
• Irritability
• Diarrhea
• Cravings

Can you Overdose on Fentanyl?

Yes, it is possible to overdose on fentanyl. Fentanyl is extremely potent, and even small amounts lead to overdose, especially when obtained illicitly. Fentanyl overdose is a leading cause of death in the United States due to the opioid epidemic. Since fentanyl is mixed with other drugs like heroin or cocaine without the user’s knowledge, it significantly increases the risk of overdose. Fentanyl overdose symptoms include slow or shallow breathing, unresponsiveness, blue or purple skin, and loss of consciousness. 

In 2021, over 71,000 opioid overdose deaths were reported, with synthetic opioids like fentanyl accounting for the majority of these fatalities, according to the Centers for Disease Control and Prevention. This trend continued into 2022, with 73,838 overdose deaths involving synthetic opioids, primarily illicitly manufactured fentanyl, as reported by the National Institute on Drug Abuse. 

What are the Overdose Symptoms of Fentanyl?  

The overdose symptoms of fentanyl include slow or shallow breathing, unresponsiveness, pinpoint pupils, cyanosis (bluish skin), loss of consciousness, limp body, cold skin, and bradycardia (slow heart rate). These symptoms are severe and are fatal without immediate intervention.

The overdose symptoms of fentanyl are as follows:

• Slow or Shallow Breathing: One of the main symptoms of fentanyl overdose is severely impaired breathing. Fentanyl suppresses the respiratory centers in the brain, leading to slow, irregular, or shallow breaths. In severe cases, this results in respiratory failure and death due to lack of oxygen.
• Unresponsiveness: Fentanyl overdose results in a person becoming unconscious and non-responsive to external stimuli. This occurs because fentanyl depresses the central nervous system, impairing the brain’s ability to maintain alertness and consciousness.
• Pinpoint Pupils: Miosis, or the constriction of the pupils, is a common sign of opioid overdose. Fentanyl causes the pupils to shrink to tiny, pinpoint sizes, which is used as a diagnostic indicator of opioid toxicity.
• Cyanosis (Bluish Skin): As fentanyl suppresses breathing and reduces oxygen intake, cyanosis develops, particularly around the lips, fingertips, and extremities. This bluish discoloration occurs as the body struggles to get enough oxygen, signaling a life-threatening condition.
• Loss of Consciousness: Fentanyl’s potent effects cause complete loss of consciousness, leaving the individual unable to be roused. This quickly progresses to a coma if not treated, as the drug depresses brain function significantly.
• Limp Body: Fentanyl overdose causes a lack of muscle tone, leaving the person’s body limp and unresponsive. This makes it difficult for emergency responders to position the person safely and perform life-saving interventions.
• Cold Skin: As the body’s circulation slows down during a fentanyl overdose, the skin feels cold to the touch. This is a sign of circulatory collapse, as the heart struggles to pump blood effectively due to the drug’s depressant effects.
• Bradycardia (Slow Heart Rate): Fentanyl overdose leads to bradycardia or a dangerously slow heart rate. This is particularly concerning because it causes cardiac arrest if the heart slows too much, further increasing the risk of death without rapid intervention.

How Much Fentanyl Will Kill You? 

The amount of fentanyl that will kill you is around 2 milligrams. This amount is extremely potent, as fentanyl is 50 to 100 times stronger than morphine, and even small doses cause fatal overdose. The exact lethal dose varies depending on an individual’s tolerance, body weight, and other factors, but for most people, 2 milligrams is a dose that leads to respiratory failure and death. This is why fentanyl is considered so dangerous, especially when it is illicitly manufactured and mixed with other substances without the user’s knowledge.

What Medication is Used to Reverse the Fentanyl Overdose? 

The medication used to reverse the fentanyl overdose is Naloxone. Naloxone is considered an antidote because it works by rapidly binding to opioid receptors, blocking and reversing fentanyl’s effects on the central nervous system. Since fentanyl suppresses breathing, Naloxone helps restore normal respiration in overdose cases. It acts quickly, within minutes, making it a life-saving intervention in opioid overdoses. However, due to fentanyl’s high potency and long-lasting effects, multiple doses of Naloxone are required. It is available in injectable and nasal spray forms (such as Narcan), and its widespread availability has been important in combating the opioid crisis.

How Does Fentanyl Compare to Other Opioids?

Fentanyl is significantly more potent compared to other opioids. While hydrocodone and oxycodone are commonly prescribed opioids for pain relief, fentanyl is 30 to 50 times stronger than hydrocodone and 50 to 100 times stronger than oxycodone. This higher potency makes fentanyl particularly dangerous, as even small amounts lead to a fatal overdose. Due to its strength, fentanyl is not prescribed for general pain relief but is used in controlled medical settings for severe pain management or during surgery. 

Is Fentanyl Stronger than Morphine?

Yes, fentanyl is stronger than morphine. Fentanyl is 50 to 100 times more potent than morphine, meaning that even very small amounts of fentanyl have a much more powerful effect on the body. This makes fentanyl highly effective in medical settings for acute pain management but also significantly increases the risk of overdose when misused. 

Is Fentanyl Stronger than Heroin?

Yes, fentanyl is stronger than heroin. Fentanyl is about 50 times more potent than heroin, which makes it much more dangerous. Even a small amount of fentanyl leads to a fatal overdose, especially when mixed with heroin or other substances without the user’s knowledge.