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Gerald F. O’Malley

, DO, Grand Strand Regional Medical Center;

Rika O’Malley

, MD, Albert Einstein Medical Center

Last full review/revision Jun 2020| Content last modified Jun 2020
Click here for the Professional Version
Topic Resources

Opioids are a class of drugs derived from the opium poppy (including synthetic variations) that are pain relievers with a high potential for misuse.

  • Opioids are used to relieve pain, but they also cause an exaggerated sense of well-being and, if used too much, dependence and addiction.

  • Taking too much of an opioid can be fatal, usually because breathing stops.

  • Urine tests can be done to check for opioids.

  • Treatment strategies include detoxification (stopping the drug), substitution (substituting another drug and gradually reducing its dose), and maintenance (substituting another drug that is taken indefinitely).

  • Ongoing counseling and support are essential in all treatment strategies.

"Opioid" is a term for a number of substances derived from the opium poppy and their synthetic and semisynthetic variations. Opioids have a legitimate medical use as powerful pain relievers. They include codeine (which has a low potential for dependence), oxycodone (alone and in various combinations, such as oxycodone plus acetaminophen), meperidine, morphine, pentazocine, and hydromorphone. Methadone taken by mouth and fentanyl taken by a skin patch are used for chronic severe pain. Heroin is a potent opioid that is illegal in the United States but is used in very limited treatment applications in other countries.

Abuse of opioids is relatively common, because these drugs are widely available and cause an exaggerated sense of well-being. People can become dependent on any opioid. (See also Drug Use and Abuse.)

Serious dependence and addiction rarely occur when people use opioids to treat a brief episode of severe pain (for example from a burn or broken bone). Although many people who use opioids to relieve pain for more than several days feel some mild symptoms of opioid withdrawal when they stop, people who take opioids for a long time to treat chronic pain are at increased risk of developing a substance use disorder.

Tolerance can develop after a few days of continued opioid use. That is, people need more and more of a drug to feel the effects originally produced by a smaller amount. People may become more tolerant to some effects than to others. Although people with a substance use disorder often have tolerance to a drug, having tolerance by itself does not mean that a person has a substance use disorder.

Did You Know...

  • Taking opioids for a brief time to relieve the pain of an immediate injury, if supervised by a doctor, rarely leads to addiction.

  • Taking opioids during pregnancy can cause addiction in the fetus and withdrawal symptoms in the newborn.


Opioids cause immediate and sometimes long-term symptoms.

Immediate effects

Opioids dull pain and are strong sedating drugs, causing people to become drowsy and quiet. Opioids may also cause euphoria.

Other, less desirable effects include

  • Constipation

  • Nausea and vomiting

  • Facial flushing

  • Itching

  • Confusion (especially in older people)

The products that result from the breakdown (metabolism) of the opioid meperidine can cause seizures.

When taken with certain other drugs, some opioids can cause a serious disorder called serotonin syndrome. This syndrome is characterized by confusion, tremors, involuntary muscle spasms or twitching, agitation, excessive sweating, and a high body temperature.


Taking too much of an opioid at once (overdose) is life threatening. In the United States in 2017, there were about 47,600 deaths from opioid overdose. Breathing becomes dangerously slow and shallow and may stop. The lungs may fill with fluid. Blood pressure, heart rate, and body temperature may decrease, and pupils constrict (becoming like pinpoints). Eventually, people become unconscious or die, usually because breathing stops. Combining opioids with alcohol or other sedatives is even more lethal.

Long-term effects

Opioids themselves do not cause many long-term complications other than dependence. Some people have minor side effects such as chronic constipation, excessive sweating, sleepiness, or decreased libido. However, many complications can result from sharing needles with another person and from unknowingly injecting other substances with the opioid.

Withdrawal symptoms

Opioid withdrawal is uncomfortable but not life threatening. Symptoms can appear as early as 4 hours after opioid use stops and generally peak within 48 to 72 hours. They usually subside after about a week, although the time frame can vary considerably depending on which opioid is used.

Each opioid is eliminated from the body at a different rate, which alters how quickly withdrawal progresses and stops. Withdrawal symptoms are worse in people who have used large doses for a long time:

  • At first, people feel anxious and crave the drug.

  • Breathing becomes rapid, usually accompanied by yawning, perspiration, watery eyes, a runny nose, dilated pupils, and stomach cramps.

  • Later, people may become hyperactive and agitated and have a heightened sense of alertness.

  • Heart rate and blood pressure increase.

Other withdrawal symptoms include

  • Gooseflesh

  • Tremors

  • Muscle twitching

  • Fever and chills

  • Aching muscles

  • Loss of appetite

  • Nausea and vomiting

  • Diarrhea

Opioid use during pregnancy is especially serious because heroin and methadone easily cross the placenta into the fetus (see Figure: How Drugs Cross the Placenta). Because babies born to addicted mothers have been exposed to the drugs their mothers have taken, they may quickly develop withdrawal symptoms, including

  • Tremors

  • High-pitched crying

  • Jitters

  • Seizures

  • Rapid breathing

If mothers take opioids immediately before labor and delivery, the baby’s breathing may be weak.


  • A doctor's evaluation

  • Sometimes urine tests

Acute opioid intoxication is usually apparent based on what people or their friends tell the doctor and on results of the physical examination. If it is not clear why a person is acting abnormally, doctors may do tests to rule out other possible causes of symptoms, such as a low blood sugar level or a head injury. Doctors can also do urine tests to check for the drug. Other tests may be done to check for complications.


An opioid overdose requires emergency treatment, but the ultimate and difficult goal of treatment is to help people control their use of opioids. Treatment can include

  • Emergency treatment

  • Detoxification

  • Possible maintenance treatment (for people who are unable to quit)

  • Rehabilitation

Emergency treatment

An opioid overdose is a medical emergency that must be treated quickly to prevent death. Breathing may require support, sometimes with a ventilator, if the overdose has suppressed breathing.

A drug called naloxone is given as an antidote to the opioid, rapidly reversing all adverse effects. It is given by injection or by nasal spray. Because some people briefly become agitated and delirious before they become fully conscious, physical restraints may be applied for a short time. Because naloxone precipitates withdrawal symptoms in people who are dependent on opioids, it is used only when necessary (as when breathing is weak).

People recovering from an overdose should be observed for several hours until the effects of naloxone have worn off to be sure that no adverse effects of the opioid remain. If people took an opioid with long-lasting effects (such as methadone or slow-release forms of other opioids), they are usually observed for a longer time.

If symptoms redevelop, people may be given another dose of naloxone, be admitted to the hospital, or both.


There are several approaches to detoxification:

  • Stopping the opioid and allowing withdrawal to run its course (cold turkey detoxification)

  • Substituting a similar but less potent drug, then gradually decreasing the dose and stopping the drug

In both detoxification strategies, treatment is usually needed to lessen the symptoms of withdrawal. The drug clonidine usually provides some relief. However, clonidine may cause side effects, such as low blood pressure and drowsiness. Stopping clonidine may itself cause withdrawal symptoms such as restlessness, insomnia, irritability, a fast heartbeat, and headaches.

Substitution typically involves giving drugs such as methadone and buprenorphine, which are then slowly decreased and eventually stopped completely.

  • Methadone is an opioid that is taken by mouth. It blocks withdrawal symptoms and the craving for other opioids, especially heroin. Because methadone’s effects last much longer than those of other opioids, it can be taken less frequently, usually once a day. The dose can then be decreased slowly. Doctors can begin the substitution, but then the use of methadone must be supervised in a licensed methadone treatment program. Large doses of methadone sometimes cause abnormal heart rhythms. Therefore, people on this drug are monitored closely when it is started or if the dose is changed.

  • Buprenorphine is a mixed opioid agonist and antagonist. That means it has some of the effects of opioids (agonist) but also blocks some of the effects of opioids (antagonist). It does not require supervision in a special program, and thus doctors who are trained in its use can prescribe it in their office. In many countries, buprenorphine has replaced methadone in detoxification programs.

Detoxification must be followed by rehabilitation to prevent a return to opioid use. Ongoing treatment may include long-term counseling and support and drugs such as naltrexone.


For people who continually return to using opioids (called chronic, relapsing opioid addiction), another approach—called maintenance—is often preferred. It involves substituting a prescribed drug at a regular dose that the user takes for a long time (months or years) rather than decreasing the dose and eventually stopping the drug. Methadone, buprenorphine, or naltrexone may be used as substitutes for opioids.

Maintaining opioid users with regular doses of one of these drugs enables them to be socially productive because they do not have to spend time getting the illicit opioid and because the drugs used do not interfere with functioning the way that illicit drug use does. For some opioid users, the treatment works. For many, lifelong maintenance is necessary.

Methadone suppresses withdrawal symptoms and the craving for the opioid without making opioid users overly drowsy or elated. However, opioid users must appear once a day at a clinic where methadone is dispensed in the amount that prevents severe withdrawal symptoms, minimizes craving, and supports daily functioning.

Buprenorphine is being used more and more because it can be prescribed by doctors in their office. Thus, opioid users do not have to go to a special clinic.

Naltrexone is a drug that blocks the effects of opioids (opioid antagonist). Before starting naltrexone, people must be fully detoxified from opioids, or a severe withdrawal reaction can occur. Depending on the dose, naltrexone’s effects last from 24 to 72 hours. Thus, the drug can be taken once a day or as few as 3 times a week. Because this drug has no opioid effects, this drug is most useful for opioid users who are strongly motivated to remain free of opioids and who are not severely dependent on opioids.


Regardless of which approach is used, ongoing counseling and support is essential. Support may include specially trained doctors, nurses, counselors, opioid maintenance programs, family members, friends, and other people with the same substance use disorder (support groups).

The therapeutic community concept emerged nearly 25 years ago in response to the problems of heroin addiction. Samaritan Daytop Village and Phoenix House pioneered this nondrug approach. Opioid users live in a communal, residential center for an extended period of time. These programs help people build new lives through training, education, and redirection. The programs have helped many people, but initial dropout rates are high.

Questions about precisely how well these programs have worked and how widely they should be applied remain unanswered. Because these programs require a lot of resources to run, many people may be unable to afford them.

More Information about Opioids

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Plain X-Rays
X-rays are high-energy radiation waves that can penetrate most substances to varying degrees. Low-dose x-rays produce images that are used for diagnosing medical conditions; high-dose x-rays are used to treat certain cancers. Which of the following is the color of bone when it appears on a low dose x-ray image? 
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