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Methadone Side Effects

Medically reviewed by Philip Thornton, DipPharm. Last updated on May 18, 2023.

Applies to methadone: oral solution, oral tablet, oral tablet for suspension. Other dosage forms:

Warning

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 InteractionThe 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

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

For Healthcare Professionals

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

Nervous system

Common (1% to 10%): Sedation, drowsiness

Frequency not reported: Headache, seizures, confusion, disorientation, lightheadedness, agitation, confusion, disorientation, dysphoria, euphoria, insomnia, hallucinations, seizures[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]

Common (1% to 10%): Edema

Uncommon (0.1% to 1%): Syncope, flushing, hypotension

Rare (less than 0.1%): Bradycardia, palpitations, QT interval prolongation, Torsades de pointes

Frequency not reported: Arrhythmias, bigeminal rhythms, cardiomyopathy, ECG abnormalities, extrasystoles, heart failure, phlebitis, QT interval prolongation, syncope, T-wave inversion, tachycardia, ventricular fibrillation, ventricular tachycardia[Ref]

Gastrointestinal

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

Very common (10% or more): Nausea, vomiting

Common (1% to 10%): Constipation

Uncommon (0.1% to 1%): Dry mouth, glossitis

Frequency not reported: Abdominal pain, anorexia, biliary tract spasm[Ref]

Other

Common (1% to 10%): Vertigo, fatigue

Uncommon (0.1% to 1%): Asthenia, hypothermia[Ref]

Hypersensitivity

Frequency not reported: Anaphylaxis[Ref]

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

Psychiatric

Common (1% to 10%): Euphoria, hallucinations

Frequency not reported: Agitation, dysphoria, insomnia, mood changes[Ref]

Endocrine

Uncommon (0.1% to 1%): Galactorrhea, dysmenorrhea, amenorrhea

Frequency not reported: Hypogonadism, decreased serum testosterone, reduced libido and/or potency, reduced ejaculate volume, reduced seminal vesicle and prostate secretions, decreased sperm motility, abnormalities in sperm morphology, gynecomastia, adrenal insufficiency, increased prolactin concentrations[Ref]

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

Genitourinary

Uncommon (0.1% to 1%): Urinary retention

Frequency not reported: Urinary hesitancy, ureteric spasm[Ref]

Respiratory

Uncommon (0.1% to 1%): Pulmonary edema, exacerbation of asthma, dry nose, respiratory depression

Frequency not reported: Pulmonary edema[Ref]

Renal

Uncommon (0.1% to 1%): Antidiuretic effect[Ref]

Hematologic

Frequency not reported: Reversible thrombocytopenia, lymphocytosis[Ref]

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

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]

Metabolic

Common (1% to 10%): Weight gain

Frequency not reported: Hypokalemia, hypomagnesemia[Ref]

Ocular

Common (1% to 10%): Miosis, dry eyes

Frequency not reported: Visual disturbances, congenital oculomotor disorders (nystagmus, strabismus)[Ref]

Dermatologic

Sweating often persists during chronic administration.[Ref]

Common (1% to 10%): Transient rash, sweating

Uncommon (0.1% to 1%): Pruritus, urticaria, other skin rashes

Rare (less than 0.1%): Hemorrhagic urticaria[Ref]

Hepatic

Uncommon (0.1% to 1%): Bile duct dyskinesia[Ref]

Local

Frequency not reported: Local tissue reactions (pain, erythema, swelling) particularly with continuous subcutaneous infusion[Ref]

Frequently asked questions

References

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

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

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

4. Cerner Multum, Inc. Australian Product Information.

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

Further information

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.

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