10 Methadone Side Effects You Should Know About

Methadone (Methadose) is a prescription opioid medication that’s most commonly used to help treat opioid use disorder. It’s also used to treat moderate to severe chronic pain.

Like all opioid medications, methadone has risks to know about. While some methadone side effects are mild, others can be severe and even life-threatening. 

Taking methadone exactly as prescribed can help minimize some of these risks. Still, if side effects do occur, knowing when to manage them at home versus when to seek care can help keep you safe.

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Methadone side effects at a glance

If you’re prescribed methadone, some side effects are more common than others. The most common methadone side effects include:

• Nausea and vomiting

• Drowsiness

• Dizziness and lightheadedness

• Sweating

• Constipation

 Potentially serious, but more rare, side effects include:

• Mood changes, such as confusion and agitation

• Adrenal insufficiency (low cortisol levels)

• Serotonin syndrome when combined with medications that increase serotonin or if high methadone doses are used

• Severe gastrointestinal problems, such as bowel obstruction

• Increased risk of seizures in people with an existing seizure condition

• Opioid withdrawal symptoms if stopped abruptly

• Low blood pressure that may lead to falls or injuries

• Increased sensitivity to pain 

Methadone also has a few boxed warnings. This is the strictest warning the FDA can give a medication. While rare, the risks discussed below can be life-threatening:

• Dependence and misuse

• Slowed breathing

• Overdose, especially when combined with other medications and substances such as benzodiazepines and alcohol

• Long QT syndrome (a heart rhythm problem)

• Accidental ingestion leading to overdose, especially in children

• Drug interactions that can increase methadone levels and the risk of overdose

Below, we’ll take a closer look at 10 of the methadone side effects mentioned above.

1. Nausea and vomiting

Nausea is a common methadone side effect. In fact, it’s common for all opioids. For some people it can lead to vomiting.

Nausea and vomiting from opioids often gets better over time as your body adjusts to the medication. In the meantime, taking methadone with food may help ease nausea. Staying hydrated and eating smaller, more frequent meals throughout the day may also help.

If these tips don’t help, your prescriber may recommend an over-the-counter (OTC) or prescription nausea medication. They may also recommend decreasing your methadone dosage or switching to another medication altogether.

EXPERT PICKS: WHAT TO READ NEXT

• Methadone versus Suboxone: Methadone and suboxone are two first-choice options for treating opioid use disorder. Learn about their differences and ways to determine which medication option is best for you.

• Avoiding alcohol: It’s important to avoid alcohol if you take opioids like methadone. Learn about the risks of this combination, including an increased risk of slowed breathing and overdose.

• Chronic pain treatment options: Opioids like methadone are just one chronic pain treatment option. Learn about the various medication and non-medication options for chronic pain here.

2. Constipation

Constipation can happen with all opioids. In fact, your prescriber may recommend taking a laxative or stool softener when you first start methadone to prevent constipation from happening in the first place.

Other methods to prevent and manage constipation include drinking plenty of fluids, exercising regularly, and increasing the amount of fiber in your diet. If your constipation continues without relief, contact your prescriber. They may recommend a prescription laxative, or they may want to evaluate you more closely to see if a more serious issue is going on.

3. Drowsiness

Methadone can commonly cause daytime drowsiness and worsen sleep quality at night. While this side effect may improve as your body adapts to methadone, it’s best to avoid activities that require alertness, like driving, when you start methadone or after dosage changes. Work with your prescriber to determine when it’s safe to resume these activities.

To minimize drowsiness from methadone, it’s best to take the lowest effective dose possible. It’s also best to avoid taking other medications that cause drowsiness. This includes benzodiazepines and other sedatives, such as sleep medications.

You should also avoid drinking alcohol. Combining these medications or alcohol with methadone can lead to extreme drowsiness, and potentially slow your breathing. This can be life-threatening.

4. Dizziness and low blood pressure

Dizziness is another common methadone side effect. It can occur on its own, or it can be a sign of low blood pressure (hypotension).

Low blood pressure from methadone is most likely when changing positions (orthostatic hypotension). You can help manage this side effect by moving slowly and being careful when going from laying down or sitting to standing. 

Dizziness and low blood pressure can increase your risk for falls. Falls can be dangerous, especially in older adults. If you’re over 65 years old, it’s important to be particularly cautious when taking opioids. 

The risk for falls may be greater when you first start methadone — before your body has adjusted to the medication. Falls or injuries are also more likely at higher doses. This is another reason to take the lowest effective dose of methadone possible. 

If you notice you feel very dizzy with methadone, or you check your blood pressure at home and it’s too low (less than 90/60 mmHg for most people), let your prescriber know immediately. 

5. Increased sweating

Sweating is another possible methadone side effect. While it’s not typically dangerous, it can affect your quality of life.

If you’re experiencing increased sweating with methadone, make sure your deodorant has an antiperspirant in it (check for an aluminum-based ingredient on the label). Use it during the day and also try applying it nightly. You can also try wearing natural fabrics and athletic clothes that have moisture-wicking fabric. If these tips don’t help, talk to your prescriber. They may recommend a prescription antiperspirant.

6. Increased sensitivity to pain

Opioid use may lead to opioid-induced hyperalgesia (OIH). This is when a person becomes more sensitive to pain after taking opioids. The exact amount of time it takes for OIH to develop isn't clear, but some research shows it can happen in as little as 1 month. However, it is more often linked to long-term opioid use.

If you’re taking methadone for pain, OIH can make it feel like methadone isn’t working for you. So talk to your prescriber if your pain seems to be getting worse. There are certain strategies they may recommend to help with OIH.

7. Dependence and misuse

Although methadone is often used to treat opioid use disorder, it can also lead to dependence and misuse. This is a possibility with all opioids. The risk is significantly higher if you use methadone in a way it isn’t prescribed, such as taking more, or taking it more often, than prescribed.

To reduce your risk for misuse, take methadone only as prescribed. If you’re still experiencing pain, talk to your prescriber about what you can do. They may recommend adjusting your dose or the addition of non-opioid pain medications. For your safety, your methadone dose should only be adjusted under your prescriber’s supervision. 

If you’re using methadone for opioid use disorder and experiencing cravings for opioids or withdrawal symptoms, let your prescriber know. They can work with you to adjust your dose if it’s safe.

If you or someone you know struggles with substance use, help is available. Call SAMHSA’s National Helpline at 1-800-662-4357 to learn about resources in your area.

8. Slowed breathing and overdose

Methadone has a risk of respiratory depression (slowed breathing) that can be life-threatening. The highest risk of this is when starting methadone or increasing the dose. Breathing problems also happen in methadone overdose. 

An opioid overdose is life-threatening. Symptoms include slowed breathing, narrowed pupils, and falling unconscious.

To reduce your risk of overdose, consider the advice below:

• Only take methadone exactly as prescribed. If you have questions about your dose, reach out to your prescriber.

• Make sure your prescriber knows your full medical history. Some medical problems may increase your risk of overdose.

• Give your prescriber and pharmacist a list of the medications you take. They can check for interactions that could increase your risk of overdose.

• Ask your prescriber before starting new medications. They’ll check to make sure they’re safe with methadone. Specific medications, such as benzodiazepines, may increase your risk of overdose.

• Avoid alcohol. Taking opioids with alcohol increases your risk of respiratory depression and overdose.

• Keep naloxone (Narcan, Zimhi) on you at all times if you or a loved one takes methadone. Naloxone can reverse an opioid overdose, and is available OTC. You can also ask your prescriber for a prescription, which may help it get covered by insurance, or allow you to use a GoodRx discount to get naloxone at a lower cost.

If you witness someone having an overdose, call 911 and administer naloxone immediately if you have it. Keep in mind methadone lasts a long time in the body, so the effects of naloxone will wear off before methadone does. This means that even if you administer naloxone, the person will still need emergency medical care.

9. Withdrawal

Suddenly stopping methadone can cause opioid withdrawal. Symptoms may include nausea or vomiting, and diarrhea. You may also experience sweating, heart palpitations, and muscle twitching. Mood-related symptoms include feeling irritable, anxious, and depressed.

If you’re interested in stopping methadone, talk to your prescriber first. If you’re taking it for opioid use disorder, it’s typically recommended to take methadone for at least a year. When/if it is time to stop it, they’ll lower your dose slowly, often over several months.

10. Heart rhythm problems

Methadone can cause a heart condition called long QT syndrome. This is when the length of time it takes your heart to reset between beats is longer than usual. In severe cases, long QT syndrome can lead to Torsades de Pointes, a life-threatening irregular arrhythmia (abnormal heartbeat).

Long QT syndrome does not always cause noticeable symptoms. But you may experience fainting, palpitations (feeling like your heart is skipping a beat), or dizziness.

Taking methadone with other medications that also cause long QT syndrome increases your risk of Torsades de Pointes. This is another reason sharing a list of all your medications with your prescriber and pharmacist is important. Additionally, higher methadone doses and a history of heart problems may increase your risk for long QT syndrome. Talk to your prescriber before taking any new medications, including OTC medications and supplements.

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Written by:

Alex Evans, PharmD, MBA

Alex Evans, PharmD, MBA, has been a pharmacist for 12 years. His first job was floating in a community chain pharmacy.

Edited by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

Reviewed by:

Bailey E. Eason, PharmD, MS, BCPS

Bailey Eason has been licensed for 6 years and has held licenses in three states (North Carolina, Virginia, and Illinois). She has held positions as a health-system pharmacy administration resident, operating room pharmacy manager, pharmacy manager of clinical operations: surgery, neurology and controlled substances, and most recently as program director  of drug diversion for a large academic health system.

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