This medication is used to treat severe ongoing pain (such as due to cancer). Methadone belongs to a class of drugs known as opioid analgesics. It works in the brain to change how your body feels and responds to pain.

Do not use this medication to relieve pain that is mild or that will go away in a few days (such as pain from surgery). This medication is not for occasional ("as needed") use.

This medication is also used to treat opioid use disorder as part of an approved treatment program. It helps prevent withdrawal symptoms caused by stopping other opioids.

See also Warning section.

Some brands of this product come with a Medication Guide. If available, read the Medication Guide provided by your pharmacist before you start using methadone and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

Take this medication by mouth on a regular schedule as directed by your doctor, not as needed for sudden (breakthrough) pain. You may take this drug with or without food. If you have nausea, it may help to take this drug with food. Ask your doctor or pharmacist about other ways to decrease nausea (such as lying down for 1 to 2 hours with as little head movement as possible).

Carefully measure the dose using a special measuring device/spoon. Do not use a household spoon because you may not get the correct dose. If your medication comes in an oral dosing syringe, use the syringe to measure the dose. Do not inject the medication. Before taking, mix the dose in at least 1 ounce (30 milliliters) of water or other liquid as directed. Drink all of the mixture right away. Do not prepare a supply in advance.

The dosage is based on your medical condition and response to treatment.

Suddenly stopping this medication may cause withdrawal, especially if you have used it for a long time or in high doses. To prevent withdrawal, your doctor may lower your dose slowly. Tell your doctor or pharmacist right away if you have any withdrawal symptoms such as restlessness, mental/mood changes (including anxiety, trouble sleeping, thoughts of suicide), watering eyes, runny nose, nausea, diarrhea, sweating, muscle aches, or sudden changes in behavior.

When this medication is used for a long time, it may not work as well. Talk with your doctor if this medication stops working well.

Though it helps many people, this medication may sometimes cause addiction. This risk may be higher if you have a substance use disorder (such as overuse of or addiction to drugs/alcohol). Take this medication exactly as prescribed to lower the risk of addiction. Ask your doctor or pharmacist for more details.

Tell your doctor if your condition does not get better or if it gets worse, or if you have any new pain.

See also Warning section.

Nausea, vomiting, constipation, lightheadedness, dizziness, dry mouth, drowsiness, or sweating may occur. Some of these side effects may decrease after you have been using this medication for a while. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

To prevent constipation, eat dietary fiber, drink enough water, and exercise. You may also need to take a laxative. Ask your pharmacist which type of laxative is right for you.

To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• interrupted breathing during sleep (sleep apnea)
• mental/mood changes (such as agitation, confusion, hallucinations)
• stomach/abdominal pain
• difficulty urinating
• signs of your adrenal glands not working well (such as loss of appetite, unusual tiredness, weight loss)

Get medical help right away if you have any very serious side effects, including:

• seizure
• severe drowsiness/difficulty waking up

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking methadone, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• brain disorders (such as head injury, tumor, seizures)
• breathing problems (such as asthma, sleep apnea, chronic obstructive pulmonary disease-COPD)
• kidney disease
• liver disease
• mental/mood disorders (such as confusion, depression, thoughts of suicide)
• personal or family history of a substance use disorder (such as overuse of or addiction to drugs/alcohol)
• stomach/intestinal problems (such as blockage, constipation, diarrhea due to infection, paralytic ileus)
• difficulty urinating (such as due to enlarged prostate)
• disease of the pancreas (pancreatitis)
• gallbladder disease

This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Avoid alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Methadone may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can rarely cause serious (rarely fatal) fast/irregular heartbeat and other symptoms (such as severe dizziness, fainting) that need medical attention right away.

The risk of QT prolongation may be increased if you have certain medical conditions or are taking other drugs that may cause QT prolongation. Before using methadone, tell your doctor or pharmacist of all the drugs you take and if you have any of the following conditions:

• certain heart problems (heart failure, slow heartbeat, QT prolongation in the EKG)
• family history of certain heart problems (QT prolongation in the EKG, sudden cardiac death)

Low levels of potassium or magnesium in the blood may also increase your risk of QT prolongation. This risk may increase if you use certain drugs (such as diuretics/"water pills") or if you have conditions such as severe sweating, diarrhea, or vomiting. Talk to your doctor about using methadone safely.

Some products may contain sugar. Caution is advised if you have diabetes. Ask your doctor or pharmacist about using this product safely.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the side effects of this drug, especially confusion, dizziness, drowsiness, slow/shallow breathing, and QT prolongation (see above).

During pregnancy, this medication should be used only when clearly needed. It may harm an unborn baby. Discuss the risks and benefits with your doctor. (See also Warning section.)

This drug passes into breast milk and may have undesirable effects on a nursing infant. Tell the doctor right away if your baby develops unusual sleepiness, difficulty feeding, or trouble breathing. Consult your doctor before breastfeeding or if you plan to stop breastfeeding.

See also Warning section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include:

• certain pain medications (mixed opioid agonist-antagonists such as butorphanol, nalbuphine, pentazocine)
• naltrexone
• samidorphan

Taking MAO inhibitors with this medication may cause a serious (possibly fatal) drug interaction. Do not take any MAO inhibitors (isocarboxazid, linezolid, metaxalone, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, safinamide, selegiline, tranylcypromine) during treatment with this medication. Most MAO inhibitors should also not be taken for two weeks before and after treatment with this medication. Ask your doctor when to start or stop taking this medication.

Other medications can affect the removal of methadone from your body, which may affect how methadone works. Examples include St. John's wort, azole antifungals (such as itraconazole), macrolide antibiotics (such as erythromycin), rifamycins (such as rifampin), drugs used to treat seizures (such as carbamazepine), among others.

The risk of serious side effects (such as slow/shallow breathing, severe drowsiness/dizziness) may be increased if this medication is taken with other products that may also cause drowsiness or breathing problems. Tell your doctor or pharmacist if you are taking other products such as other opioid pain or cough relievers (such as codeine, hydrocodone), alcohol, marijuana (cannabis), drugs for sleep or anxiety (such as alprazolam, lorazepam, zolpidem), muscle relaxants (such as carisoprodol, cyclobenzaprine), or antihistamines (such as cetirizine, diphenhydramine).

Check the labels on all your medicines (such as allergy or cough-and-cold products) because they may contain ingredients that cause drowsiness. Ask your pharmacist about using those products safely.

This medication may interfere with certain lab tests (such as amylase/lipase levels), possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, give them naloxone if available, then call 911. If the person is awake and has no symptoms, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: slow/shallow breathing, slow heartbeat, coma.

Do not share this medication with others. Sharing it is against the law.

This medication has been prescribed for your current condition only. Do not use it later for another condition unless told to do so by your doctor. A different medication may be necessary in those cases.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets. See also Warning section.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. For more details, read the Medication Guide, or consult your pharmacist or local waste disposal company.