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Opioids ˈō-pē-ˌȯid

By Patrick G. O’Connor, MD, MPH, Professor of Medicine; Chief, Section of General Internal Medicine, Yale University School of Medicine

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  • 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 may involve stopping the drug abruptly, substituting another drug and gradually reducing its dose to nothing, or substituting another drug that is taken indefinitely.

  • Ongoing counseling and support are essential to controlling opioid addition.

Opioids have a legitimate medical use as powerful pain relievers (see Opioid Analgesics). 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, which is illegal in the United States but is used in very limited treatment applications in other countries, is one of the strongest opioids.

Opioids are common drugs of abuse because they are widely available and cause an exaggerated sense of well-being. People can become dependent on any opioid.

Although many people who use opioids to relieve pain for more than several days feel some symptoms of withdrawal when they stop, serious dependence and addiction rarely occur when opioid use is medically supervised.

Tolerance can develop after 2 to 3 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 of some effects than of others. People who have developed tolerance may show few signs of drug use and function normally in their usual activities as long as they have access to drugs.

Did You Know...

  • Taking opioids 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.


Immediate Effects

Opioids are strong sedating drugs, causing people to become drowsy and quiet. Opioids may also cause euphoria. They dull pain and may enhance sexual pleasure. Other effects, such as constipation, nausea, vomiting, and itching, are less desirable. Opioids may cause confusion, especially in older people. In larger doses, they cause lethargy or sleep and may slow the heart rate and breathing rate.

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. Breathing becomes dangerously slow and shallow, and the lungs may fill with fluid. Blood pressure, heart rate, and body temperature may decrease, and pupils constrict (becoming like pinpoints). People may become unconscious or die, usually because breathing stops.

Long-Term Effects

Opioids themselves do not cause many long-term complications other than dependence. However, many complications can result from sharing needles with another person and from unknowingly injecting other substances with the opioid (see Complications From Drug Injection).

Withdrawal Symptoms

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 increases. Other symptoms include gooseflesh, tremors, muscle twitching, fever and chills, aching muscles, loss of appetite, and diarrhea.

Opioid use during pregnancy is especially serious because heroin and methadone easily cross the placenta into the fetus. 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, and rapid breathing. If mothers take opioids immediately before labor and delivery, the baby’s breathing may be weak.


Doctors base the diagnosis on symptoms and urine tests to check for the drug. Other tests may be done to check for complications.


An opioid overdose requires emergency treatment. The ultimate and difficult goal of treatment is to help addicts control their addiction. Detoxification can help people get through the initial period of drug withdrawal, but further assistance is usually required to prevent people from returning to using drugs. Those who continually return to using opioids may require maintenance treatment.

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 intravenously as an antidote to the opioid, rapidly reversing all adverse effects. 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 clearly 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 two basic approaches:

  • 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

With detoxification, treatment is usually needed to lessen the symptoms of withdrawal. Clonidine usually provides some relief. However, clonidine may cause low blood pressure and drowsiness. Stopping clonidine may cause restlessness, insomnia, irritability, a fast heartbeat, and headaches. Sometimes drugs that block the effects of opioids, such as naltrexone, are needed to help people remain free of the opioid after they are fully detoxified.

Drugs that can be substituted, then stopped include methadone and buprenorphine. 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, usually at a clinic.

Buprenorphine is a partial opioid agonist. That means it has some of the effects of opioids but blocks some of the effects of opioids. 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.


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 that the user takes for a long time. Methadone, buprenorphine, or naltrexone may be used.

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

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

Buprenorphine is being used more and more because it can be prescribed by doctors in their office. Thus, addicts 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, some addicts do not want to use it. This drug is most useful for addicts 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 addiction (support groups).

The therapeutic community concept emerged nearly 25 years ago in response to the problems of heroin addiction. Daytop Village and Phoenix House pioneered this nondrug approach. Addicts live in a communal, residential center for an extended period of time. These programs help addicts 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.

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