Definition

Opioid-based medicines include morphine, oxycodone, and synthetic (man-made) opioid narcotics, such as fentanyl. They are often prescribed to treat pain after an injury, surgery, or a dental procedure. Sometimes, they are used to treat severe cough or diarrhea. The illegal drug heroin is also an opioid. When abused, opioids cause a person to feel relaxed and intensely happy (euphoria). In short, the medicines are used to get high.

Opioid intoxication is a condition in which you're not only high from using the medicine, but you may also have body-wide symptoms that can make you ill or impaired.

Alternative Names

Intoxication - opioids; Opioid abuse - intoxication; Opioid use - intoxication

Causes

Opioid intoxication may occur when a health care provider prescribes an opioid, but:

• The dose is too high for the person.
• The provider doesn't know the person is already taking another opioid at home.
• The provider prescribes a sleep medicine (sedative) in addition to the opioid.
• The provider doesn't know that another provider already prescribed an opioid or sedative.
• The person has a health problem, such as a liver or kidney problem, that may easily result in intoxication.

In people who use opioids to get high, intoxication may be caused by:

• Using too much of the medicine
• Using an opioid with certain other medicines, such as sleep medicine or alcohol
• Taking the opioid in ways not normally used, such as smoked or inhaled through the nose (snorted)

Symptoms

Symptoms depend on how much of the medicine is taken.

Symptoms of opioid intoxication can include:

• Altered mental status, such as confusion, delirium, or decreased awareness or responsiveness
• Breathing problems (breathing may slow and eventually stop)
• Extreme sleepiness or loss of alertness
• Nausea and vomiting
• Small pupils

Exams and Tests

Tests that are ordered depend on the provider's concern for additional medical problems. Tests may include:

• Blood tests
• CT scan of the brain, if the person is having seizures or might have a head injury
• Electrocardiogram (ECG) to measure electrical activity in the heart
• Chest x-ray to check for pneumonia
• Toxicology (poison) screening

Treatment

The provider will measure and monitor the person's vital signs, including temperature, pulse, breathing rate, and blood pressure. Symptoms will be treated as appropriate. The person may receive:

• Breathing support, including oxygen, or a tube that goes through the mouth into the lungs and attachment to a breathing machine (ventilator)
• Intravenous fluids (fluids given through a vein)
• Medicine called naloxone (Evzio, Narcan) to block the effect of the opioid on the central nervous system
• Other medicines as needed

Since the effect of the naloxone is often short, your health care team may monitor you for 4 to 6 hours in the emergency department. People with moderate to severe intoxication will often be admitted to the hospital for 24 to 48 hours.

A mental health evaluation is needed if the person is suicidal.

Outlook (Prognosis)

Many factors determine the short- and long-term outcome after opioid intoxication. Some of these are:

• The degree of poisoning, for example, if the person stopped breathing, and for how long
• How often the medicines are used
• Effect of impurities mixed in with illegal substances
• Injuries that occur as a result of the medicine use
• Underlying medical conditions

Possible Complications

Health problems that may occur include any of the following:

• Permanent lung damage
• Seizures, tremors
• Reduced ability to think clearly
• Unsteadiness and difficulty walking
• Infections or even permanent damage of the organs as a result of injection use of the drug

References

Aronson JK. Opioid receptor agonists. In: Aronson JK, ed. Meyler's Side Effects of Drugs. 16th ed. Waltham, MA: Elsevier; 2016:348-380.

Brust JCM. Effects of drug abuse on the nervous system. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 87.

National Institute on Drug Abuse website. Opioids. nida.nih.gov/research-topics/opioids. Updated November 2024. Accessed July 11, 2025.

National Institute on Drug Abuse website. Heroin research report: what are the medical complications of chronic heroin use? nida.nih.gov/publications/research-reports/heroin/what-are-medical-complications-chronic-heroin-use. Updated July 2011. Accessed April 16, 2025.

Nikolaides JK, Thompson TM. Opioids. In: Walls RM, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 151.