• Addiction & recovery

Side Effects of Methadone

David Schwartz, MD

October 22, 2021


Methadone has been approved by the U.S. Food and Drug Administration (FDA) to treat opioid use disorder (OUD) and pain management since the 1970s. And since then, methadone has been listed as an essential medication by the World Health Organization (WHO). Methadone maintenance treatment (MMT) is an essential and cost-effective treatment for individuals with opioid dependence to manage severe withdrawal symptoms while reducing the risk of relapse. Today, methadone continues to be one of the most widely used medications for opioid use disorder (MOUD) in the United States. 

Methadone is a schedule II medication available in tablets, powder, and liquid forms. Similar to most opioid medications, methadone comes with a list of potential side effects that can range from mild to severe.


How Does Methadone Work?

Methadone is a long-acting opioid that works by interacting with opioid receptors in the brain to reduce opioid withdrawal symptoms. Methadone also functions by blocking the effects of opioids such as heroin, codeine, and morphine to reduce the risk of relapse during recovery. 

Methadone’s effects are slower than those of other opioids. When administered as part of a MOUD treatment program, it does not generate a “high” in opioid-dependent individuals. Methadone takes effect within 30-45 minutes after administration, peaks around 2-4 hours, and gradually builds up in the body for as long as 1-3 days. 

Who Should Not Receive Methadone?

Certain health conditions can hinder the efficacy of methadone and generate negative reactions. Hence, individuals must inform their healthcare provider of the following health conditions to ensure safe treatment.

  • Liver or kidney disease
  • Severe asthma or difficulty breathing 
  • Head injuries, brain tumors, or seizures
  • Heart problems
  • Urination problems 
  • Allergic to methadone
  • Blockage in the stomach or intestines
  • Problems in the gallbladder, pancreas, or thyroid
  • Mental health conditions
  • Pregnant or breastfeeding


Common Side Effects of Methadone 

The milder, more common side effects of methadone tend to disappear within a few days or a couple of weeks and include symptoms such as:

  • Vomiting       
  • Nausea                
  • Profuse sweating   
  • Stomach pains              
  • Constipation         
  • Sexual problems         
  • Changes in appetite        
  • Slow breathing rates 
  • Changes in sleep patterns 
  • Itchy skin/ skin rashes         
  • Headache       
  • Dry mouth        
  • Weight gain 
  • Mood changes         
  • Vision problems
  • Flushing  
  • Restlessness
  • Dizziness 

If the symptoms persist or worsen with time, consult your healthcare provider before you discontinue the medication.

Side Effects of Methadone - Eleanor Health

Severe Side Effects of Methadone  

Methadone is administered based on strict protocols to mitigate the risk of misuse and severe side effects.

Severe side effects of methadone include:

  • Shallow breathing
  • Fast or irregular heartbeat
  • Light-headedness or fainting 
  • Severe drowsiness
  • Chest pain        
  • Confusion        
  • Hallucinations
  • Severe allergic reactions 
  • Seizures
  • Overdose        
  • Coma         
  • Death

Some of the severe side effects of methadone can indicate a medical emergency. Individuals are advised to stop taking the medication and contact a healthcare professional immediately if they experience severe side effects. 


Long-Term Effects of Methadone

The longer and more frequently a person uses methadone, the more likely they are to experience long-term side effects. Since methadone is an opioid medication, prolonged use can lead to physical dependence and increased tolerance. 

Prolonged use of methadone can also cause:

  • Mood changes
  • Cardiovascular problems
  • Respiratory problems such as reduced breathing rates
  • Brain, liver, and nerve damage
  • Changes in sexual function and menstruation (in women)
  • Increased participation in risky behaviors


Symptoms of Methadone Overdose

Methadone is a potent opioid that has the potential to cause an overdose if taken in large doses. A methadone overdose can also occur when the medication is combined with other central nervous system depressants such as benzodiazepines or alcohol. 

Symptoms of a methadone overdose include:

  • Pinpoint pupils         
  • Weak pulse
  • Cold, clammy skin
  • Dizziness
  • Hypertension
  • Discoloration of the nails and fingertips 
  • Low blood pressure
  • Blue lips and fingernails        
  • Loss of consciousness   
  • Shortness of breath   
  • Cardiac arrest 

Methadone overdose is a medical emergency. Not recognizing the signs and receiving medical treatment can result in fatal consequences. Make sure to contact your healthcare professional or poison control if you think you have consumed too much methadone. In the event of a methadone overdose, Narcan/naloxone should be administered to the person who has overdosed immediately. The next step would be to call 911 (even if the person appears to wake up or come out of it because the effects of naloxone could wear off) and wait with the person for an ambulance to arrive. A methadone overdose can be reversed with Evzio injectable or Narcan nasal spray. Consult your healthcare practitioner about keeping prescription naloxone on hand in case of an emergency.


Symptoms of Methadone Withdrawal 

Individuals who abruptly stop taking methadone after prolonged use may experience withdrawal symptoms as a result of its potent properties. Hence, individuals will be gradually weaned off methadone to help mitigate withdrawal symptoms.

Symptoms of methadone withdrawal can include:

  • Vomiting         
  • Nausea      
  • Abdominal pain            
  • Fever        
  • Anxiety 
  • Sweating        
  • Runny nose 
  • Rapid heart rate
  • Muscle aches    
  • Irritability        
  • Paranoia        
  • Extreme fatigue       
  • Restlessness     
  • Watery eyes      
  • Weight loss       
  • Goosebumps       
  • Diarrhea    
  • Depression         
  • Hallucinations       

Symptoms of methadone withdrawal generally appear within 24-36 hours after the last dose. Certain individuals may not experience withdrawal symptoms until several days after the last dose due to its long-acting nature.


Methadone Interactions That Increase the Risk of Side Effects

Using methadone alongside benzodiazepines and other CNS depressants can increase the risk of side effects such as respiratory depression, profound sedation, coma, and death. 

Methadone can also negatively interact with the following medications:

  • Sedatives
  • Hypnotics
  • Tranquilizers
  • General anesthetics
  • Opioid medications
  • Other pain medications
  • Alcohol 

In 2017, the U.S Food and Drug Administration (FDA) advised that opioid maintenance medications such as methadone should not be withheld from individuals taking benzodiazepines or other CNS depressants. Although the combined use of these medications enhances the risk of side effects, the harm caused by untreated opioid use disorder can outweigh these risks. And careful medication management by health care professionals can significantly reduce the risk of negative interactions.


Alternatives to Methadone Treatment

While methadone has been used to treat opioid use disorder in the United States since the 1970s, other medications are just as effective in the battle against substance use disorders. The following are some FDA-approved medications that are used in substance use disorder treatments:

  • BuprenorphineBuprenorphine has many advantages for individuals with opioid use disorder and those looking for an alternative to methadone treatment. Buprenorphine has a ceiling effect as a partial opioid agonist, which reduces respiratory depression and its risk of an accidental overdose. In terms of medication retention and decreased opioid use, buprenorphine-assisted treatment is just as effective as methadone.
  • Naltrexone – Intramuscular extended-release Naltrexone is a medication utilized in the treatment of OUD and AUD. Naltrexone isn’t an opioid, nor is it addictive, nor does it cause any withdrawal effects during cessation. Naltrexone blocks the euphoric and sedative effects of opioids such as heroin, morphine, and codeine. And as a result, reduces or prevents opioid cravings with a minimum risk of misuse.
  • VivitrolVivitrol is a non-addictive opioid antagonist that suppresses the brain’s response to opioids by reducing cravings. Vivitrol treatment is only utilized after the successful completion of a detox program.
  • SuboxoneSuboxone is the newest methadone substitute that incorporates buprenorphine (a partial opioid agonist) with naloxone (an opioid antagonist). Suboxone, like methadone, reduces cravings and the risk of relapse. And since buprenorphine reaches a ceiling effect at higher doses, it reduces the risk of overdose.
  • Campral – Also known by its brand name Acamprosate, it’s designed to help decrease cravings during alcohol use disorder treatment. Campral helps restore the chemical balance in the brain during treatment. Individuals experiencing anxiety, insomnia, or restlessness during alcohol cessation can greatly benefit from this medication.  
  • Chantix – Chantix, also known as Varenicline, is a prescription medicine used to aid smoking cessation. Chantix may be used alone or as a combination with other medications. New studies have suggested its efficacy in treating alcohol use disorder and opioid use disorder.

The right medication can help you maintain a positive state of mind and get you through the difficult periods of your recovery with greater success. And the treatment programs at Eleanor Health are designed to meet the highest clinical safety and care levels. 

If you are seeking help with your loved one’s addiction, contact us today or complete our quick contact form below, to speak with an addiction treatment specialist.

If you need help with your substance use disorder, we are here to help you build your confidence and momentum towards the future you want. We provide treatment services for adults with alcohol, opioid, and other substance use disorders. We are currently located in LouisianaMassachusettsNew JerseyNorth CarolinaOhio, Texas, and Washington.

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