Fentanyl is roughly 100 times more potent than morphine and 50 times more potent than heroin. Side effects include drowsiness, weakness, and dry mouth, among others.

Fentanyl is the most potent opioid pain reliever available for use in medical treatment. This information comes from the Centers for Disease Control and Prevention (CDC). Although healthcare professionals consider fentanyl safe and effective when a person uses it in a monitored medical setting, the drug still carries a high potential for misuse, also known as abuse.

Some people make designer fentanyl analogs, which are nearly identical to the original drug. Since fentanyl and its analogs are incredibly potent, accidental overdoses and deaths are increasingly common.

People often either mix analogs with, or substitute them, for heroin. Because fentanyl is much more potent than heroin, there is also a hugely increased risk of overdose and death.

In this article, we will discuss the medical uses of fentanyl and its side effects. We will also cover misuse of fentanyl, addiction, and the risk of overdose.

Fentanyl is a Schedule II prescription narcotic analgesic that is as much as 50–100 times more potent than morphine and 30–50 times more potent than heroin.

As a prescription, fentanyl is available under the brand names Actiq, Duragesic, and Sublimaze. People with prescriptions for the drug typically take it as a shot or a patch on their arm. A person may also take it through a throat lozenge.

People with substance use disorders can also use synthetic fentanyl illegally. For example, they can get it as powders or pills or put it into containers such as eyedroppers or nasal sprays. Street names for the drug include Apache, China Girl, Goodfellas, Great Bear, Poison, and Tango & Cash.

How does fentanyl affect the brain?

As with other opioid drugs, fentanyl binds to the receptors in the brain that affect pain and emotions. This causes feelings of well-being (euphoria) and relaxation, and it also relieves pain.

Fentanyl affects everyone differently. The effects are dependent on an individual’s:

  • size
  • weight
  • overall state of health

The effects are also dependent on:

  • the amount a person takes
  • whether they take it in combination with other drugs
  • whether the person is used to taking opioids

Over time, however, the brain adapts to fentanyl, making it hard for a person to experience positive emotions from anything but the drug. This can lead to addiction.

Medically prescribed fentanyl is available in a variety of formulations, including:

  • lozenges
  • lollipops
  • oral or nasal sprays
  • injections

Medical uses for fentanyl include:

  • anesthesia for patients undergoing heart surgery or for patients with poor heart function
  • management of breakthrough cancer pain in patients who are already receiving opioid medication for underlying, persistent pain
  • pain management in people who have persistent, moderate-to-severe chronic pain requiring continuous, around-the-clock opioids
  • pain relief for people who are already taking narcotic analgesics or who are already opioid-tolerant

Fentanyl patch

For continuous delivery, fentanyl is administered through a transdermal patch that adheres to the skin. The patch works by slowly releasing fentanyl through the skin into the bloodstream over 20–72 hours.

Doctors can only administer the fentanyl patch to people who are already tolerant to opioid therapy of similar strength. Because it has already been absorbed through the skin, fentanyl can continue to be effective for 13–24 hours after the patch is removed. However, this depends on how each person’s skin absorbs the drug.

Older people are more likely than younger individuals to experience adverse effects, especially the respiratory depressant effects of fentanyl. Healthcare professionals must exercise extreme caution and regularly monitor people in this age group.

Side effects of fentanyl include:

Adverse effects associated with transdermal fentanyl patches include:

  • discoloration
  • rash
  • itching
  • swelling at the site of application

People with substance use disorders can obtain fentanyl by diverting it from legitimate medical supplies, or by manufacturing it in illegal laboratories. They may take it orally, smoke it, snort it, or inject it. No one method of use is safer than another.

Even discarded fentanyl patches can still contain significant amounts of the drug. People with opioid use disorders can remove the gel contents from discarded patches and eat it, place it under the tongue, smoke it, or inject it.

Many fentanyl analogs may be much more potent than heroin, making the former even more dangerous than the latter.

Often, other illegal drugs, such as heroin and cocaine, may be mixed with fentanyl, making them much more potent. People with substance use disorders may not know about the addition of fentanyl, which puts them at a higher risk of accidental overdose or death.

Treatment options for fentanyl addiction

Treatment for fentanyl addiction is the same as for any opioid use disorder and depends on the severity of the addiction. Treatment may include inpatient or outpatient detox, medication treatments for managing cravings and relapse, and residential and outpatient behavioral treatment programs.

Medications may include buprenorphine and methadone, which affect the same receptors in the brain that are impacted by fentanyl. This helps reduce the symptoms of withdrawal. A doctor may also choose to prescribe naltrexone, which is a different medication that stops fentanyl from affecting the body.

Which medication is right for a person may depend on many factors. A person should discuss the best course of treatment with their doctor. They may also want to consider talking with a therapist.

This may also help them develop a healthier lifestyle and support them in their consistent medication use, if medication is part of their treatment. Therapy options may include:

  • cognitive behavioral therapy, which works on changing behavior and managing triggers and anxiety.
  • contingency management, which gives point vouchers for negative drug tests
  • motivational interviewing, which counsels the individual based on their unique needs and their conflicting feelings regarding their need to change in order to overcome addiction

As with any opiate, there is a risk of dependency, tolerance, misuse, and addiction. Physical dependence results in withdrawal symptoms when individuals abruptly stop taking the drug.

Withdrawal symptoms usually start within 12 hours of the last dose of fentanyl and can last 1 week or more. An individual in withdrawal may experience:

  • dilated pupils
  • vomiting and diarrhea
  • goosebumps
  • a runny nose
  • hot and cold flashes
  • chills
  • anxiety
  • agitation
  • insomnia
  • severe generalized pain

People who use fentanyl swiftly develop a tolerance to high doses, meaning that more of the drug is needed to achieve the desired effect.

Repeated opioid use often results in addiction, which is a chronic relapsing condition that goes beyond physical dependence and is characterized by uncontrollable drug-seeking behavior despite harmful and negative consequences.

Opioid-dependent individuals sometimes use fentanyl as a substitute for heroin. However, it is a very dangerous substitute because of its marked potency and the inability for people to gauge dosages, resulting in frequent deadly overdoses.

Pure fentanyl powder is also very difficult to dilute appropriately, often resulting in a dangerously strong mixture. It can be deadly even for people who have a high opioid tolerance. In some cases, death occurs so quickly that people are found with a needle still in the site of injection.

Fentanyl use can result in accidental death even with just one dose, especially if a person accidentally takes it incorrectly.

Signs and symptoms of a fentanyl overdose include:

  • slow or shallow breathing
  • slow heartbeat
  • severe sleepiness
  • cold, clammy skin
  • trouble walking or talking
  • feeling faint, dizzy, or confused
  • unresponsiveness

Many fatal overdoses thought to be from heroin have actually been from fentanyl. Even a small dose of fentanyl, such as 2 milligrams, can be lethal depending on how tolerant someone is and their body size. Coroners’ offices and state crime laboratories do not test for fentanyl or its analogs unless given a specific reason to do so.

The Food and Drug Administration has warned that deaths and overdoses have occurred in people using both the brand-name product Duragesic and generic transdermal fentanyl patches. Most recently, it warned that children are at particular risk for accidental death from exposure.


An overdose of fentanyl is an emergency. A person exhibiting the symptoms of overdose should get immediate medical attention. If they do not, they may get hypoxia. This means a person’s brain is not getting enough oxygen. The condition can lead to coma and even death.

The treatment for overdose is usually naloxone. However, someone will need to administer it as soon as possible. The medication will block the effect of the fentanyl. However, since fentanyl is very strong, a person may need several doses of the drug.

Fentanyl is an extremely potent opioid that offers significant pain relief to those who live with severe acute or chronic pain conditions. However, it is also capable of causing considerable harm or death to people with opioid use disorders or people who are accidentally exposed to the drug.

Fentanyl key facts

  • What it is: Fentanyl is an opioid analgesic that is 100 times more potent than morphine.
  • How it is used: It is taken legally in prescription form to treat severe pain or illegally in synthetic form. People can also find it mixed with other illegal drugs. However, they may not always know that it is present.
  • How it feels: Fentanyl reduces pain and causes euphoria and relaxation.
  • What it causes: It carries a high risk of dependence and addiction, as well as risk overdose due to extreme potency.

Some patients and healthcare professionals may not be fully aware of the dangers of this very strong narcotic. All of society, including families, schools, the medical community, law enforcement, and government officials, should be aware of the potentially lethal outcomes of improper medical and illicit fentanyl use.