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Methadone Side Effects

Medically reviewed by Philip Thornton, DipPharm. Last updated on Mar 19, 2024.

Applies to methadone: oral solution, oral tablet, oral tablet for suspension.

Other dosage forms:

Important warnings This medicine can cause some serious health issues

Oral route (tablet for suspension)

Deaths due to too-rapid titration, drug interactions, or cardiac and respiratory side effects have occurred with methadone use for opioid dependence.

Respiratory depression is the main hazard associated with methadone administration.

QT interval prolongation and serious arrhythmias (torsades de pointes) have been observed during treatment with methadone.

Only approved hospitals and pharmacies can dispense oral methadone for the treatment of narcotic addiction.

Oral route (tablet; solution)

ing: Addiction, Abuse And Misuse; Life-Threatening Respiratory Depression; Accidental Ingestion; Life-Threatening QT Prolongation; Neonatal Opioid Withdrawal Syndrome; Interactions With Drugs Affecting Cytochrome P450 Isoenzymes; Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants; And Treatment For Opioid Addiction

Addiction, Abuse, and Misuse

Methadone hydrochloride tablets expose patients and other users to the risks of opioid addiction, abuse, and misuse, which can lead to overdose and death.

Assess each patient’s risk prior to prescribing methadone hydrochloride tablets, and monitor all patients regularly for the development of these behaviors and conditions.

Life-Threatening Respiratory Depression

Serious, life-threatening, or fatal respiratory depression may occur with use of methadone hydrochloride tablets.

The peak respiratory depressant effect of methadone occurs later, and persists longer than the peak analgesic effect, especially during the initial dosing period or following a dose increase.

Monitor for respiratory depression, especially during initiation of methadone hydrochloride tablets or following a dose increase.

Proper dosing and titration are essential and methadone hydrochloride should only be prescribed by healthcare professionals who are knowledgeable in the use of methadone for toxification and maintenance treatment of opioid addiction.

Accidental Ingestion

Accidental ingestion of even one dose of methadone hydrochloride tablets, especially by children, can result in a fatal overdose of methadone.Life-Threatening QT Prolongation: QT interval prolongation and serious arrhythmia (torsades de pointes) have occurred during treatment with methadone.

Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.

Closely monitor patients with risk factors for development of prolonged QT interval, a history of cardiac conduction abnormalities, and those taking medications affecting cardiac conduction for changes in cardiac rhythm during initiation and titration of methadone hydrochloride tablets

Neonatal Opioid Withdrawal Syndrome

Neonatal opioid withdrawal syndrome (NOWS) is an expected and treatable outcome of use of methadone hydrochloride tablets during pregnancy.

NOWS may be life-threatening if not recognized and treated in the neonate.

The balance between the risks of NOWS and the benefits of maternal methadone hydrochloride use may differ based on the risks associated with the mother’s underlying condition, pain, or addiction.

Advise the patient of the risk of NOWS so that appropriate planning for management of the neonate can occur.Cytochrome P450 Interaction. The concomitant use of methadone hydrochloride tablets with all cytochrome P450 3A4, 2B6, 2C19, 2C9 or 2D6 inhibitors may result in an increase in methadone plasma concentrations, which could cause potentially fatal respiratory depression.

In addition, discontinuation of concomitantly used cytochrome P450 3A4, 2B6, 2C19, or 2C9 inducers may also result in an increase in methadone plasma concentration.

Follow patients closely for respiratory depression and sedation, and consider dosage reduction with any changes of concomitant medications that can result in an increase in methadone levels.

Risks from Concomitant Use with Benzodiazepines or Other CNS Depressants

Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death.Reserve concomitant prescribing of methadone and benzodiazepines or other CNS depressants for use in patients for whom alternative treatment options are inadequate.Limit dosages and durations to the minimum required.Follow patients for signs and symptoms of respiratory depression and sedation.

If the patient is visibly sedated, evaluate the cause of sedation, and consider delaying or omitting the daily methadone dose.Conditions For Distribution And Use Of Methadone Products For The Treatment Of Opioid Addiction:For detoxification and maintenance of opioid dependence, methadone should be administered in accordance with the treatment standards cited in 42 CFR Section 8, including limitations on unsupervised administration.

Serious side effects of methadone

Along with its needed effects, methadone may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking methadone:

Incidence not known

  • black, tarry stools
  • bleeding gums
  • blood in the urine or stools
  • blurred vision
  • bulging soft spot on the head of an infant
  • change in the ability to see colors, especially blue or yellow
  • changes in skin color
  • chest discomfort or pain
  • confusion
  • cough
  • coughing that sometimes produces a pink frothy sputum
  • darkening of the skin
  • decreased urine output
  • diarrhea
  • difficult, fast, noisy breathing
  • difficulty with swallowing
  • dilated neck veins
  • dizziness
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • dry mouth
  • extreme fatigue
  • fainting
  • fast, slow, or irregular heartbeat
  • headache
  • hives, itching, or skin rash
  • increased sweating
  • increased thirst
  • irregular heartbeat
  • irregular, fast or slow, or shallow breathing
  • loss of appetite
  • mental depression
  • muscle pain or cramps
  • nausea or vomiting
  • numbness or tingling in the hands, feet, or lips
  • pain
  • pale or blue lips, fingernails, or skin
  • pinpoint red spots on the skin
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • seizures
  • sweating
  • swelling of the face, fingers, feet, or lower legs
  • tenderness
  • trouble breathing
  • trouble sleeping
  • trouble urinating
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • weight gain

Get emergency help immediately if any of the following symptoms of overdose occur while taking methadone:

Symptoms of overdose

Other side effects of methadone

Some side effects of methadone may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Incidence not known

  • absent, missed, or irregular menstrual periods
  • anxiety
  • blurred or loss of vision
  • confusion about identity, place, and time
  • constipation
  • decreased interest in sexual intercourse
  • disturbed color perception
  • double vision
  • false or unusual sense of well-being
  • halos around lights
  • inability to have or keep an erection
  • irritability
  • lack or loss of strength
  • loss in sexual ability, desire, drive, or performance
  • night blindness
  • overbright appearance of lights
  • redness, swelling, or soreness of the tongue
  • restlessness
  • stopping of menstrual bleeding
  • tunnel vision
  • weight changes
  • welts

Managing side effects (general information)

For healthcare professionals

Applies to methadone: compounding powder, injectable solution, intravenous solution, oral concentrate, oral solution, oral tablet, oral tablet dispersible.

General

The major adverse reaction of this drug is respiratory depression; to a lesser degree, systemic hypotension, respiratory arrest, shock, cardiac arrest, and death have occurred. The most commonly observed adverse reactions include lightheadedness, dizziness, sedation, nausea, vomiting, and sweating.[Ref]

Cardiovascular

Cases of QT interval prolongation and Torsades de pointes have occurred during treatment; these cases appear to be more commonly associated with higher dose treatment (greater than 200 mg per day). There have been some cases in patients receiving lower doses and in these cases contributing factors such as concomitant medications and/or clinical conditions were present. In vivo studies have confirmed this drug effects the QT interval and in vitro studies have shown it inhibits cardiac potassium channels.[Ref]

Gastrointestinal

Constipation often persists during chronic administration; nausea, and vomiting appear to be more frequent after oral administration.[Ref]

Other

Hypersensitivity

Anaphylaxis has been reported with ingredients contained in methadone products.[Ref]

Psychiatric

Endocrine

Hypogonadism, decreased serum testosterone, and reproductive effects are thought to be related to chronic opioid use.[Ref]

Genitourinary

Respiratory

Renal

Hematologic

Reversible thrombocytopenia has been described in opioid addicts with chronic hepatitis.[Ref]

Nervous system

Metabolic

Ocular

Dermatologic

Sweating often persists during chronic administration.[Ref]

Hepatic

Local

References

1. (2002) "Product Information. Dolophine (methadone)." Lilly, Eli and Company

2. Cerner Multum, Inc. "UK Summary of Product Characteristics."

3. (2007) "Product Information. Diskets (methadone)." Cebert Pharmaceuticals Inc

4. Cerner Multum, Inc. "Australian Product Information."

5. (2021) "Product Information. Methadose (methadone)." Mallinckrodt Medical Inc

Frequently asked questions

Further information

Methadone side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

Medical Disclaimer