medication for opioid use disorder (MOUD), intervention used in the treatment of opioid use disorder (OUD), a condition characterized by addiction to opioid drugs. Medication for opioid use disorder (MOUD) can reduce opioid use and cravings, improve social functioning, and reduce the risk of death from opioid overdose. Drugs used as MOUD include buprenorphine, methadone, and naltrexone. More than 16 million people worldwide are estimated to be affected by OUD; however, only about 10 percent of that population receives MOUD.

Historical developments

In the 1960s, methadone was found to be an effective treatment for opioid dependence (later known as OUD). In 1966, the discovery of buprenorphine, which has a more favorable safety profile than methadone, opened the way to improving treatment of opioid dependence. In the early 1990s, clinical trials demonstrated the effectiveness of buprenorphine in reducing illicit opioid use. By 1997, the U.S. National Institutes of Health (NIH) was supporting methadone maintenance treatment for decreasing opioid use, improving social engagement, reducing the likelihood of crime, and decreasing the spread of AIDS, hepatitis, and other viral diseases. Thus, the NIH subsequently promoted increased access to methadone treatment for opioid users.

In the United States, barriers to methadone and other narcotic drugs were set by the Narcotic Addict Treatment Act of 1974. In 2000 the Drug Addiction Treatment Act reduced those barriers.

Effects and administration

MOUD exerts its effects by interacting with opioid receptors located on neurons in the brain. The receptors are the same as those used by opioid drugs, such as heroin, fentanyl, and oxycodone. At the receptors MOUD may act as either an agonist, a partial agonist, or an antagonist. Agonists, such as methadone, and partial agonists, such as buprenorphine, activate opioid receptors in a manner similar to that of opioids, but without eliciting the same level of euphoria. When agonist medications are properly dosed, intense opioid cravings and withdrawal symptoms subside. Both methadone and buprenorphine are taken daily.

Antagonist medications, such as naltrexone, work by interfering with or blocking opioid receptor activity. Since they do not activate opioid receptors, such medications are not addictive. They can, however, cause patients to become more sensitive to opioids than they were prior to treatment. In the event of relapse, antagonist-induced reductions in tolerance can significantly increase overdose risk from amounts of opioids that are equal to or lower than those taken in the past. Naltrexone for OUD is administered as a monthly injection.

Methadone is dispensed only by a federally certified and accredited opioid treatment program. By contrast, both buprenorphine and naltrexone can be delivered in other settings, such as residential and outpatient treatment programs.

Are you a student?
Get a special academic rate on Britannica Premium.
Frannie Comstock The Editors of Encyclopaedia Britannica

methadone, potent synthetic narcotic drug that is the most effective form of treatment for addiction to heroin and other narcotics. Methadone first became available at the end of World War II. Similar to morphine in its analgesic effect, it was originally used in medicine to alleviate severe pain. Methadone is used in the form of its hydrochloride salt, which is a white, crystalline powder with a bitter taste. It is soluble in water, in alcohol, and in chloroform.

Methadone’s usefulness in treating heroin addiction was discovered in the 1960s. It is now routinely used on a daily, long-term (maintenance) basis as a substitute drug given to persons who were formerly or who would otherwise be addicted to heroin. It is given orally once a day. Methadone’s usefulness as a heroin substitute stems from several important effects the drug has. First and foremost, when taken daily it prevents a former heroin addict from feeling withdrawal symptoms and it suppresses his drug hunger for heroin. Second, methadone itself causes no euphoric effects whatsoever, unlike heroin, so the person feels no disruptive psychological craving for it. Third, the human body does not develop a tolerance for methadone, unlike heroin, so methadone doses of the same (rather than increasing) size can be taken for long periods of time. Fourth, when used on a maintenance basis, methadone actually blocks the euphoric effects, or “high,” produced by heroin, thus robbing this drug of its psychological attractiveness to the former addict. Finally, methadone’s lack of euphoric effects and its 24-hour period of action enable persons maintained on it to lead relatively normal lives involving work, schooling, and normal family and social relations.

Methadone is an addictive drug, but one can more easily cease using it than heroin. Because of this, methadone is sometimes used to detoxify heroin addicts; the addict switches from heroin to a high daily dose of methadone, which is then gradually reduced over several weeks until the patient is drug-free. In this way the severe withdrawal symptoms encountered in abruptly quitting heroin are avoided.

Methadone-maintenance therapy is markedly successful in keeping addicts off the use of heroin or whatever other narcotic they were using, but there is considerably less success in enabling such people to stop using methadone as well and be drug-free.

The Editors of Encyclopaedia Britannica