Methadone Side Effects, Interactions, & Warnings

Manish Mishra, MBBS

Medically Reviewed By: Manish Mishra, MBBS

on March 11, 2023

In Ohio, methadone is effective for treating pain relief, opioid withdrawal, and opioid addiction. Nevertheless, methadone is still a potent opioid that can lead to severe side effects, physical dependence, and addiction when misused.

Methadone is an opioid analgesic prescription drug used to treat severe pain and opioid addiction. It eases opioid withdrawal symptoms that occur once you stop abusing opiates/opioids. Methadone is available under the brand name Methadose.

Methadone works by binding to opioid receptors in the central nervous system and changing how the brain responds to pain. As a long-acting opioid agonist, methadone also prevents severe withdrawal symptoms and reduces drug cravings.

Although methadone is FDA-approved for treating opioid use disorder, it’s still a relatively strong drug that can lead to opioid dependence and overdose when misused. 

Methadone Side Effects

Some methadone side effects are relatively mild, short-term, and common while others are severe, rare, and long-term.

Common side effects of methadone may include:

  • headache
  • stomach pain
  • dry mouth
  • difficulty urinating
  • mood changes
  • vision problems
  • difficulty falling asleep or staying asleep
  • lightheadedness
  • drowsiness
  • constipation
  • nausea
  • vomiting
  • hallucinations
  • loss of appetite

Severe Side Effects Of Methadone

Methadone can also lead to severe, long-term side effects. However, these serious side effects are rare and may include:

  • seizures
  • itching
  • hives
  • skin rash
  • swelling of the face, mouth, tongue, or throat
  • respiratory depression/trouble breathing
  • extreme drowsiness
  • severe muscle stiffness
  • chest pain
  • fainting
  • low blood pressure

Methadone Drug Interactions

Some medications do not mix well with methadone. When certain medications are combined, serious side effects and an increased risk of overdose may occur.

Some of the substances that shouldn’t be mixed with methadone include:

  • over-the-counter supplements
  • buprenorphine 
  • benzodiazepines
  • cyclobenzaprine 
  • certain medications for HIV including abacavir (Ziagen) and darunavir (Prezista)
  • lithium 
  • naloxone (Narcan)
  • naltrexone
  • rifampin (Rifadin)
  • selective serotonin-reuptake inhibitors such as citalopram (Celexa), escitalopram (Lexapro), and fluoxetine (Prozac)
  • serotonin and norepinephrine reuptake inhibitors such as desvenlafaxine (Pristiq) and venlafaxine (Effexor)
  • tramadol (Conzip and Ultram)
  • monoamine oxidase (MAO) inhibitors including linezolid and methylene blue,

Methadone Warnings

Methadone also comes with several warnings related to addiction, overdose, contraindications, and withdrawal.


Becoming addicted to methadone is a real concern. While the drug is used to treat opioid addiction, abusing it can increase the risk of opioid use disorder, which is defined by tolerance and physical dependence. 

Other signs and symptoms to look out for if you suspect a loved one is addicted to methadone include:

  • taking more of the drug than prescribed
  • taking methadone regularly, even if it’s unnecessary
  • continuing to use the drug despite negative consequences
  • ignoring responsibilities at work, school, and home
  • taking the drug secretly or lying about amount of use

Methadone Overdose

Overdosing on methadone is also a major risk especially if you’re abusing the drug or mixing it with other substances. Overdosing on methadone can be life-threatening. If you or a loved one are experiencing any of the following symptoms of opioid overdose, call 911 immediately:

  • pinpoint pupils 
  • slow or shallow breathing
  • cool, clammy, or blue skin
  • unable to respond or wake up
  • sedation
  • limp muscles
  • chest pain or discomfort
  • increased sweating
  • unusual drowsiness
  • slow or irregular heartbeat


There are also several medical conditions that methadone can actually make worse. If you have any of the following health issues, talk to your healthcare provider before you start taking methadone:

  • brain disorders like head injury, tumors, and seizures
  • breathing problems like asthma and sleep apnea
  • chronic obstructive pulmonary disease (COPD)
  • kidney disease
  • liver disease
  • mental health disorders like depression and anxiety
  • personal or family history of a substance use disorder
  • difficulty urinating 
  • pancreatitis
  • gallbladder disease
  • blockage in your intestine
  • paralytic ileus 
  • enlarged prostate 
  • Addison’s disease
  • seizures
  • thyroid disease

Methadone Withdrawal Symptoms

If you regularly abuse or take high doses of methadone, you’ll likely build up a physical dependence. When that happens and you stop using, methadone withdrawal symptoms are likely to occur and may include:

  • fever
  • anxiety
  • muscle aches 
  • nausea and vomiting
  • rapid heartbeat
  • irritability
  • paranoia
  • diarrhea
  • cravings
  • insomnia
  • hallucinations
  • depression
  • increased blood pressure
  • teary eyes
  • runny nose

If you or a loved one live with substance abuse or drug addiction and need treatment in Ohio, Ohio Recovery Center can help. We offer a variety of addiction treatment options, including medical detoxification, to ensure you get a treatment plan that fits your specific needs 

To learn more about our treatment programs, please contact us today.

  1. Food and Drug Administration (FDA) — METHADOSE Label
  2. National Library of Medicine: MedlinePlus — Methadone

Written by Ohio Recovery Center Editorial Team

© 2024 Ohio Recovery Center | All Rights Reserved

* This page does not provide medical advice.

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