Methadone

Methadone

Definition

Methadone is classified as an opioid (an analgesic that is used for severe pain). In the United States, methadone is also known as dolophine, methenex and methadose.

Purpose

Methadone is used in the long-term maintenance treatment of narcotic addiction . Both heroin and methadone are opioids; as such, methadone and heroin bind to the same places in the brain . Methadone, however, is the opioid of choice for the treatment of narcotic addiction since it is longer lasting and patients don't experience the "high" associated with the drug of abuse. In opioid maintenance therapy, a person addicted to heroin receives methadone instead of heroin. Essentially, the person is switched from an opioid that gives a "high" to an opioid that does not. The dose of methadone may then be decreased over time so that the person can overcome his or her opioid addiction without experiencing withdrawal symptoms, or, after a person has received methadone for a period of time, he or she may choose to go through detoxification with clonidine . In the United States, methadone treatment is associated with a significant reduction in predatory crime, improvement in socially acceptable behavior, and psychological well-being.

Methadone may also be prescribed for pain relief, but in these cases, the physician must note this use on the prescription.

Description

Methadone has been used successfully to treat narcotic addiction for over twenty years in the United States. Methadone is the only FDA-approved agent in its class for the maintenance treatment of narcotic addiction.

Methadone for maintenance treatment is dispensed in methadone clinics. The program needs to be registered with the Drug Enforcement Agency. For admission to methadone treatment in clinical programs, federal standards mandate a minimum of one year of opiate addiction as well as current evidence of addiction. Pregnant, opiate-addicted females can be admitted with less than a one-year history and AIDS patients are routinely accepted. New patients must report daily, take medication under observation, and participate in recommended psychosocial treatments.

Some studies have shown that over 50% of patients in methadone clinics do not abuse drugs in the first month of treatment. After ten months, however, the success rate drops to approximately 20%. Moreover, major depression is a powerful predictor of relapse in methadone treatment. If the patient has dual addictions (alcoholism along with the heroin addiction, for example), management of the other addiction increases the success rate of the methadone therapy. Proper psychiatric and psychological treatment can considerably improve methadone treatment outcome.

In the cases of pregnant women who are addicted to heroin, detoxification (discontinuing the opioid altogether) is associated with a high rate of spontaneous abortions in the first trimester and premature delivery in the third trimester. Therefore, pregnant women can be in methadone maintenance programs if they are at risk of returning to drug dependence. These women should receive the lowest effective dose, receive appropriate prenatal care, and be warned about risks of returning to drug abuse, as well as the dangers associated with withdrawal effects of methadone. Methadone is associated with lower birth weights and smaller head circumference, but it has never been shown that this has any impact on the infants' further development.

Methadone is available in 5-, 10-, and 40-mg tablets and a solution.

Recommended dosage

The initial dose of methadone is 40 mg daily administered in single or divided doses. After achieving initial dosing of about 40 mg daily, the dose should be increased since there is evidence that the relapse rate is significantly lower in patients on 80-100 mg daily rather than 40-50 mg daily. The stabilization to maintenance dosing requires one to three months.

The minimum effective dose is 60 mg daily taken at once or in divided doses. Patients on lower maintenance doses have recently been studied and have shown shorter treatment retention and have continued heroin use. If patients are stable on methadone for six months or longer, their methadone dose should not be increased by 33% or over, as this sudden increase in dose is associated with an increase in craving for the drugs that were previously abused. Some heroin patients need to be on doses up to 180 mg daily to provide adequate maintenance and to prevent relapse.

Precautions

Methadone should not be used in patients who have had hypersensitivity to methadone. Patients who experience an allergic reaction to other opioids, which may include a generalized rash or shortness of breath, such as morphine, hydromorphone, oxymorphone, or codeine may try methadone. They are less likely to develop the same reaction since methadone has a different chemical structure. Methadone should be administered carefully in patients with pre-existing respiratory problems, history of bowel obstruction, glaucoma, renal problems, and hyperthyroidism.

As stated, pregnant women can be in methadone maintenance programs if they are at risk of returning to drug dependence. Methadone is associated with smaller birth weights and smaller head circumference.

Side effects

Most adverse effects of methadone are mild and seen only in the beginning of therapy. Initially, patients may develop sedation and analgesia. It takes about four to six weeks for tolerance to these effects to develop. Tolerance to constipation and sweating may take longer to develop.

A few patients who are on larger doses of methadone may experience respiratory problems. These patients also may experience unwanted cardiac effects.

A small number of patients report a decrease in libido, impotence, and premature, delayed, or failed ejaculation. There are a few reports of occasional menstrual irregularities in female patients on methadone.

Interactions

Life-threatening interactions with other drugs have not been identified. One of the initial side effects of methadone could include dizziness and sedation, and these effects are worsened if the patient is also taking other narcotics, benzodiazepines, or is consuming alcohol.

Monoamine oxidase inhibitors (MAOIs), such as Parnate (tranylcypromine ) and Nardil (phenelzine ), should be avoided by people taking methadone. Medications such as naltrexone and naloxone should never be used concurrently with methadone. People must stop taking methadone for seven to 10 days before starting naltrexone or naloxone.

See also Alcohol and related disorders; Disease concept of chemical dependency; Opioids and related disorders

Resources

BOOKS

Albers, Lawrence J., M.D., Rhoda K. Hahn, M.D., and Christopher Reist, M.D. Handbook of Psychiatric Drugs. 2001–2002. Laguna Hills, CA: Current Clinical Strategies Publishing, 2001.

Kay, Jerald. Psychiatry: Behavioral Science and Clinical Essentials. Philadelphia: W. B. Saunders Company, 2000.

PERIODICALS

Curran, Valarie H. "Additional Methadone Increases Craving for Heroin: A Double-Blind, Placebo-Controlled Study of Chronic Opiate Users Receiving Methadone Substitution Treatment." Addiction 94 (1999):665-74.

Strain, Eric. "Moderate-vs High-Dose Methadone in the Treatment of Opioid Dependence." Journal of the American Medical Association 281 (1999):1000-5.

Ajna Hamidovic, Pharm.D.