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Fentanyl Side Effects

Peter Manza, PhD profile image
Reviewed By Peter Manza, PhD • Updated Aug 14, 2023 • 4 cited sources

Overdose is one of the most severe fentanyl side effects. More than 67,000 people died in 2021 due to an overdose of drugs like fentanyl.[1] Many of these deaths were accidental. 

Understanding the side effects of this dangerous drug is important. But it’s even more critical for those who misuse this drug to get help. Medication for Addiction Treatment (MAT) programs could save your life. 

What Are Fentanyl’s Common Side Effects?

Fentanyl is a prescription painkiller designed for short-term use to treat acute pain. Unfortunately, some people misuse this drug to get high. And many others buy drugs (like heroin) that contain fentanyl they didn’t know was included.

Like all opioids, fentanyl changes almost every part of your brain and body. While many people use fentanyl for euphoria or pain relief, other problems could quickly occur. These are fentanyl’s known side effects.[2]

Mental health side effects include the following:

  • Agitation
  • Anxiety
  • Depression
  • Hallucinations
  • Vivid dreams

Physical side effects include the following:

  • Back pain 
  • Chest pain 
  • Drowsiness
  • Dry mouth 
  • Facial flushing 
  • Gas
  • Heartburn
  • Insomnia 
  • Seizures
  • Sexual changes
  • Stomach pain
  • Swelling in the hands and feet 
  • Tremors 
  • Urinary retention
  • Vision changes
  • Weight loss

The Dangers of Fentanyl Overdose

Fentanyl is one of the most powerful opioids available, and that power comes with very real dangers. 

Opioids latch tightly to receptors within the central nervous system, slowing breathing rates and pulse. Those changes come with very real physical changes outsiders can see. 

Symptoms of an overdose include the following:[3]

  • Stupor
  • Small pupils
  • Clammy skin
  • Blue-tinged skin or fingernails
  • Respiratory failure 

Without prompt treatment, a fentanyl overdose can be life-threatening. A very slow breathing rate and a heart working much too slowly can lead to tissue death. Your cells need a regular infusion of oxygen delivered by your heartbeats, and without it, they can die. 

People in the middle of a fentanyl overdose can look like they’re sleeping or napping. But people who look closely may notice that they’re not breathing enough.

Naloxone is an opioid antagonist, capable of rendering fentanyl inside the body inactive. A quick spray of the medication into the nostrils can reverse an overdose in progress. Researchers say up to 100% of opioid overdoses can be reversed by bystanders delivering naloxone.[4]

An opioid overdose reversal isn’t a treatment for opioid use disorder (OUD). People with a history of OUD need long-term care through a Medication for Addiction Treatment program. Therapies like Suboxone can amend chemical imbalances caused by fentanyl, allowing you to live a healthy life in sobriety. And therapy can help you to build the foundation of a balanced life in recovery.

Reviewed By Peter Manza, PhD

Peter Manza, PhD received his BA in Psychology and Biology from the University of Rochester and his PhD in Integrative Neuroscience at Stony Brook University. He is currently working as a research scientist in Washington, DC. His research focuses on the role ... Read More

  1. Drug Overdoses. National Safety Council. Accessed March 2023.
  2. Fentanyl. U.S. National Library of Medicine. January 2021. Accessed March 2023.
  3. Fentanyl. United States Drug Enforcement Administration. Accessed March 2023.
  4. Naloxone Dosage for Opioid Reversal: Current Evidence and Clinical Implications. Therapeutic Advances in Drug Safety. January 2018. Accessed March 2023.

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