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  • Long-Term Effects Of Methadone | Side Effects & Warnings

    side of methadone sad mad sitting on a couch

    Methadone is an opioid analgesic (pain relief medication) that can treat severe pain. It’s often prescribed under the brand names Methadose and Dolophine.

    The United States Food and Drug Administration (FDA) has approved it to treat opioid addiction, also known as opioid use disorder. Specifically, the drug can ease opioid withdrawal symptoms and cravings. This form of treatment is called methadone maintenance treatment

    However, because methadone is an opioid medication itself, it comes with its own side effects and health risks, especially with long-term use. 

    Side Effects Of Methadone

    The most common side effects of methadone include:

    • dry mouth
    • headache
    • stomach pain
    • trouble urinating
    • constipation 
    • weight gain
    • vision issues
    • mood changes
    • insomnia

    The drug can also cause more serious side effects, such as:

    • sweating
    • extreme drowsiness
    • nausea and/or vomiting
    • diarrhea
    • loss of appetite
    • fever
    • rash, hives, and/or itching
    • swollen face, eyes, mouth, tongue, or throat
    • irregular menstruation
    • decreased sexual desire or ability
    • confusion
    • hallucinations (seeing, hearing, or feeling things that aren’t there)
    • trouble breathing
    • increased heart rate

    If you experience these or other unusual side effects, contact your health care provider right away.

    To avoid or decrease side effects, always follow your doctor’s instructions for taking methadone. Never take it for a longer period of time than prescribed. 

    Also, before taking methadone, tell your doctor about any health concerns you’ve experienced. Issues such as head injuries, irregular heartbeats, or breathing problems may make you more likely to experience the drug’s serious side effects. 

    Methadone Warnings

    Along with unpleasant side effects, methadone can cause neonatal issues, addiction, withdrawal symptoms, and overdose as a result of long-term abuse. 

    Neonatal Issues

    If you use methadone while pregnant, your baby could experience potentially fatal withdrawal symptoms after birth. Seek medical advice immediately if your baby displays any of these symptoms:

    • high-pitched cry
    • vomiting
    • diarrhea
    • abnormal sleep
    • lack of weight gain
    • hyperactivity
    • irritability
    • uncontrollable shaking of a part of the body

    Similarly, if you use methadone while breastfeeding, the drug may pass into your breastmilk and cause your baby to experience the following side effects:

    • trouble breastfeeding
    • unusual sleepiness
    • limpness
    • trouble breathing

    Contact your baby’s doctor right away if you notice these or other unusual symptoms. Also, talk to your doctor before weaning your baby. You may need to wean slowly so your baby doesn’t experience withdrawal symptoms from the lack of methadone. 


    You may become addicted to methadone if you take it for a long time or abuse it. Abuse occurs when you don’t follow your doctor’s instructions for taking methadone. 

    For example, you might mix it with other drugs, take it without a prescription, or take higher doses than prescribed.

    Signs of methadone addiction include:

    • mood swings
    • withdrawing from family and friends
    • neglecting responsibilities at work or school 
    • feeling unable to stop using methadone despite wanting to
    • tolerance, which means you need increasingly higher doses of the drug to achieve the desired effects
    • physical dependence, which means your body relies on the drug to function normally

    Withdrawal Symptoms

    If you’re physically dependent on methadone and you try to stop using it, you may experience physical and mental withdrawal symptoms such as:

    • sweating
    • chills
    • larger pupils
    • anxiety
    • irritability
    • loss of appetite
    • watery eyes
    • runny nose
    • insomnia
    • nausea and/or vomiting
    • diarrhea 

    To avoid or decrease the severity of withdrawal symptoms, talk to your doctor before you stop taking methadone. In most cases, your doctor will recommend gradually lowering your dosage instead of quitting cold turkey. This strategy puts less stress on your body. 


    Overdose can occur if you take too much methadone. 

    You face a higher risk of overdose if you mix the medication with other drugs, especially central nervous system (CNS) depressants

    Common CNS depressants include benzodiazepines, such as Klonopin and Xanax; non-benzodiazepine sedative hypnotics, such as Ambien and Lunesta; and barbiturates, such as Luminal and Nembutal. 

    Common signs of methadone overdose include:

    • cool, clammy skin
    • respiratory depression (slow, shallow breathing) 
    • muscle limpness
    • smaller pupils
    • loss of consciousness 

    If you or someone you know experiences these symptoms, seek emergency medical attention immediately; a methadone overdose can be life-threatening. 

    To stay safe, people who use methadone and their loved ones should keep naloxone on hand. Naloxone is a medication that can rapidly reverse the effects of an opioid overdose.

    If you or someone you love struggles with methadone use, please contact an Ark Behavioral Health specialist to learn about our detoxification and drug addiction treatment programs.

    Written by Ark Behavioral Health Editorial Team
    ©2024 Ark National Holdings, LLC. | All Rights Reserved.
    This page does not provide medical advice.

    National Institute on Drug Abuse - Prescription CNS Depressants DrugFacts
    Substance Abuse and Mental Health Services Administration (SAMHSA) - Methadone
    U.S. National Library of Medicine: MedlinePlus - Methadone

    Medically Reviewed by
    Kimberly Langdon M.D.
    on March 23, 2022
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