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How Much Stronger Is Fentanyl vs. Heroin?

Elena Hill, MD, MPH profile image
Medically Reviewed By Elena Hill, MD, MPH • Updated Aug 14, 2023 • 7 cited sources

Fentanyl is a synthetic opioid. The potency of fentanyl varies greatly depending on the batch. However, some fentanyl can be 50 times stronger than heroin. It is one of the most potent opioids that exists. 

While it has some legitimate medical uses, fentanyl is one of the most dangerous substances contributing to the opioid epidemic. Synthetic opioids like fentanyl are causing a massive spike in opioid-related overdose deaths in the United States. 

How Much Stronger Is Fentanyl Compared to Heroin?

The potency of opioids is typically assessed by first determining their relative strength compared to morphine, often referred to as morphine maintenance equivalents (MME). Of the opioids commonly misused, fentanyl ranks one of the highest MME, with a relative potency of 100 to 1. [1] 

Depending on the quality of the fentanyl batch, it can be as high as 50 times stronger than heroin [2] While both drugs are dangerous and addictive, fentanyl is undeniably the more potent and dangerous. Fentanyl’s widespread availability is largely responsible for the spike in opioid-related deaths in recent years.

A Brief History of Fentanyl

Fentanyl was developed in 1959 as a legal intravenous anesthetic. It was (and still is) used during anesthesia for procedures requiring pain control and sedation. [3] It also comes in the form of a patch that is approved for severe chronic pain. 

Because it is comparatively very cheap to manufacture compared to natural opiates or heroin, it grew in popularity. Rather than import opiate products from other countries, synthetic opioids like fentanyl can be produced and distributed cheaply and more readily within the United States. These factors have led to the widespread proliferation of illicit Fentanyl in recent years. Fentanyl and its analogues are now considered some of the most serious problematic drugs in the opioid epidemic, in large part due to their significant overdose risk.[3]

Why Is Fentanyl Used So Often Today?

Fentanyl is easier and cheaper to produce than heroin. Therefore, it is favored by distributors because it is more profitable. It is also sometimes favored by opioid users because it is less expensive than opioid pills or even illicit heroin. 

On the other hand, distributors often market their fentanyl as “heroin” in order to sell it at a higher price. This means many people may believe they are purchasing heroin and are really getting fentanyl. Fentanyl is also  sometimes used to cut other drugs without a buyer’s knowledge to make a drug more potent and addictive. [4,5] 

Dangers of Fentanyl

Many more individuals are using fentanyl either knowingly or unknowingly. However, even those who do so knowingly may not realize how much more potent fentanyl is compared to the heroin they are accustomed to. This leads to a greatly increased risk of overdose and accidental death. 

This is in addition to various other problematic side effects of fentanyl, including vomiting, urinary retention, confusion, severe drowsiness, dizziness, constipation, cognitive decline and memory loss. 

Injecting fentanyl can lead to increased risk of blood borne disease transmission including HIV and Hepatitis B or C. It can also increase the risk of infection, chronic skin ulceration, necrosis, bone infections (osteomyelitis), bloodstream infections (bacteremia) and heart infection (endocarditis). 

Fentanyl use can also result in serious problems in a person’s personal and work life. The possession and use of illicit opioids (and especially the illegal sale of these opioids) can have severe legal repercussions.[6] 

Overdose Symptoms

Symptoms of a fentanyl overdose are similar to other opioids, and include the following:

  • Pupillary constriction
  • Cold and clammy skin
  • Confusion or stupor
  • Unconsciousness, leading to coma
  • Stopped or slowed breathing
  • Unresponsiveness 

Ultimately, opioid overdose leads to severe respiratory depression and even death [7] This is a medical emergency and warrants immediate professional medical attention. 

Call 911 and administer naloxone (Narcan) if available. Naloxone can reverse opioid overdoses. If you or someone you love engages in opioid misuse, you should have naloxone on hand to use in an emergency. Even if naloxone is used, professional medical help is still needed since the overdose could return once the naloxone wears off. When in doubt, it is always best to use Naloxone and to call 911 immediately if you suspect someone of overdose.

Medically Reviewed By Elena Hill, MD, MPH

Elena Hill, MD; MPH received her MD and Masters of Public Health degrees at Tufts Medical School and completed her family medicine residency at Boston Medical Center. She is currently an attending physician at Bronxcare Health Systems in the Bronx, NY where ... Read More

  1. WHO Guidelines for the Pharmacological and Radiotherapeutic Management of Cancer Pain in Adults and Adolescents. World Health Organization. 2018. Accessed March 2023.
  2. Fentanyl Facts. Centers for Disease Control and Prevention. February 2022. Accessed March 2023.
  3. Fentanyl. Drug Enforcement Administration. April 2020. Accessed March 2023.
  4. Heroin Uncertainties: Exploring Users’ Perceptions of Fentanyl-Adulterated and -Substituted ‘Heroin’. International Journal of Drug Policy. August 2018. Accessed March 2023.
  5. Why Would Anyone Cut Heroin With Fentanyl? It's Cheap, These Researchers Say. NBC News. December 2018. Accessed March 2023.
  6. Opioids. Johns Hopkins Medicine. Accessed March 2023.
  7. Opioid Overdose. StatPearls. September 2022. Accessed March 2023.

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