Methadone belongs to the class of medications called narcotic analgesics (pain relievers). These pain relievers are also known as opioid analgesics. Methadone is used to relieve chronic (long-term) severe pain when less potent pain relievers are not effective. It should never be used by someone who has not tried other pain relievers. Opioids decrease pain by working on the brain to increase pain tolerance. For pain relief, methadone works quickly and stays in the body for a much longer time than other opioid analgesics.

Methadone is also used in combination with medical and social services to help people break the habit of drug abuse, when the drug being used is another opioid, such as a heroin or morphine-like medication. Because it is active in the body for a long period of time, the withdrawal effects of methadone can be milder than those of heroin or other abused drugs.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The usual starting dose of methadone for adults is 2.5 mg to 10 mg taken by mouth every 4 hours for the first 3 to 5 days. After this, your doctor will determine the appropriate dose for you, to be taken every 8 to 12 hours. If you are over 65 years old, your doctor may recommend that you take your methadone once daily. Doses of methadone for pain relief vary widely and depend on individual circumstances. If you have not taken opioid pain relievers before, methadone is NOT appropriate. Discuss other alternatives with your doctor.

If you are taking methadone tablets, swallow the tablets whole with fluids. Cutting, breaking, chewing, crushing, or dissolving methadone tablets can result in dangerous adverse events, including overdose and death.

After a certain dose of methadone has been taken for a period of time, the body may get used to it and a higher dose of methadone is needed to relieve the pain. Generally, your doctor will try to find the dose of methadone that will give you acceptable pain relief without an unacceptable level of side effects. This helps to reduce the side effects of the medication and allows for the dose to be adjusted upwards if needed. Always check with your doctor if you feel your medication isn't working well anymore.

Over time, this medication may produce tolerance and physical dependence as your body becomes used to the drug. Tolerance occurs when a dose that used to provide acceptable pain relief is no longer effective, and higher doses are required to achieve the same level of pain relief. Physical dependence is a state where the body will go into withdrawal if the medication is stopped suddenly. If you have been taking methadone on a regular basis for a long period of time, talk to your doctor before stopping the drug, as withdrawal effects can occur.

Tolerance and physical dependence are not the same as addiction. Addiction is defined as a psychological need to use the medication for reasons other than pain relief. Although people may become addicted to this medication, it is most common for people who have had addictions to other substances in the past.

The starting dose of methadone for opioid detoxification is determined by the dose needed to suppress withdrawal symptoms from other opioid medications. This is almost always done in a hospital setting. Slowly, the dose of methadone will be reduced by your doctor, keeping in mind that the objective is often to totally withdraw the narcotic with minimal withdrawal symptoms.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor.

If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice. If you miss several doses in a row, contact your doctor for advice on how to restart the medication.

The liquid form of methadone will be provided to you in juice or another drink such as Tang or grape Kool-Aid. Store the medication in the refrigerator. If the medication is mixed in apple juice, return any unused medication to the pharmacy for disposal after 7 days. If it is mixed in another beverage, return the unused portion after 14 days. Use an oral syringe to measure each dose of the liquid, as it gives a more accurate measurement than household teaspoons.

Store the tablet form of this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Keep methadone in a safe place to protect it from being stolen. This medication can be fatal if it is taken by anyone other than the person for whom it was prescribed.

Cherry Flavour Concentrate
Each 1 mL of red, cherry-flavoured liquid concentrate, contains 10 mg of methadone. Nonmedicinal ingredients: natural and artificial cherry flavor, citric acid anhydrous, FD&C Red No. 40, D&C Red No. 33, methylparaben, poloxamer 407, propylene glycol, propylparaben, purified water, sodium citrate dihydrate, and sucrose.

Sugar-Free Concentrate
Each 1 mL of dye-free, sugar-free, unflavoured liquid concentrate, contains 10 mg of methadone. Nonmedicinal ingredients: citric acid anhydrous, purified water, sodium benzoate.

Do not take this medication if you:

• are allergic to methadone or any ingredients of the medication
• are experiencing acute alcoholism or delirium tremens
• are experiencing acute asthma, other obstructive airway disease, or cor pulmonale
• are experiencing acute respiratory depression
• are experiencing mild pain or pain that is expected to last only a short period of time
• have a blockage of the gastrointestinal tract, particularly paralytic ileus
• have a head injury, a brain tumour, or increased pressure inside the head or spinal cord
• have a medication regimen (current or completed in the last 14 days) that includes MAO inhibitors such as phenelzine or tranylcypromine
• have severe depression of the central nervous system (i.e., sedation)
• have severe diarrhea that is caused by antibiotics or poisoning
• have suspected abdominal conditions that may require surgery
• have not been taking opioids regularly
• are pregnant or breast-feeding, in labour, or delivering

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• constipation
• decreased ability or interest in sexual activity
• dizziness
• drowsiness
• dry mouth
• flushing
• headache
• itching
• lightheadedness
• nausea
• poor appetite
• sweating
• trouble sleeping
• vomiting
• weakness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• breathing difficulty
• decreased coordination
• fainting
• fast, slow, or irregular heartbeat
• low blood pressure (e.g., dizziness, lightheadedness or fainting, especially after standing up)
• symptoms of arrhythmia (e.g., rapid, pounding heartbeat; dizziness; lightheadedness; fainting)
• severe constipation with abdominal pain and nausea
• vision changes

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of overdose
• cold, clammy skin
• confusion
• convulsions (seizures)
• dizziness (severe)
• drowsiness (severe)
• hallucinations
• low blood pressure
• nervousness or restlessness (severe)
• pinpoint-sized pupils
• slow heartbeat
• slow or troubled breathing
• weakness (severe)
• signs of serotonin toxicity (e.g., agitation, confusion, diarrhea, fever, overactive reflexes, poor coordination, restlessness, shivering, sweating, talking or acting with excitement you cannot control, trembling or shaking, twitching)
• slow, shallow, or weak breathing
• withdrawal symptoms (e.g., nausea, vomiting, diarrhea, anxiety, shivering, cold and clammy skin, body aches)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Abdominal (stomach) conditions: As with other narcotic medications, methadone slows down bowel movement and it may make the diagnosis of abdominal conditions more difficult or it may worsen these conditions. If you have abdominal problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Abnormal heart rhythms: This medication can cause abnormal heart rhythms. Certain medications can increase the risk of a type of abnormal heart rhythm called QT prolongation, and should not be used in combination with methadone. If you have heart disease and abnormal heart rhythms, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Accidental use: When methadone is used by anyone other than the person for whom it was prescribed, the effects of the medication may be fatal. Children are especially at risk of a fatal overdose. Keep this medication out of sight and reach of children.

Adrenal gland problems: Adrenal glands produce chemical messengers that are responsible for the normal function of the body’s organs, including how your body responds to injury or stress. On rare occasions, methadone, like other opioid medications, may cause your adrenal gland to function improperly. This risk increases if you have been taking opioids for longer than a month. Your doctor may monitor your adrenal gland function.

Alcohol and other medications that cause drowsiness: Do not combine methadone with alcohol or other medications (e.g., antidepressants, sleeping pills, anxiety medications) that cause drowsiness. Additional drowsiness and suppressed breathing can occur and be dangerous and possibly fatal.

Asthma and other respiratory conditions: Methadone can cause severe and life-threatening breathing problems. It can also cause increased breathing difficulty for people having an acute asthma attack or those with chronic obstructive pulmonary disease (chronic bronchitis, emphysema) or other conditions that affect breathing. If you have asthma or any other breathing disorder, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Blood pressure: Methadone can cause severely decreased blood pressure, which is often made worse by other medications that are being taken at the same time. When first starting methadone, it is a good idea to slowly rise from lying or sitting positions, to give the blood pressure the time needed to adjust to the new posture. Standing up or sitting up quickly may cause severe dizziness and even fainting.

Dependence and withdrawal: This medication may be habit forming if taken for long periods of time. Drug abuse is not a problem for people who require this medication for pain relief. Physical dependence (a need to take regular doses to prevent physical symptoms) has been associated with other narcotic analgesics.

Although methadone is also used to help people withdrawing from other habit-forming medications, withdrawal symptoms may be experienced if the dose is significantly reduced or suddenly discontinued.

These symptoms include irritability, sleep problems, agitation, diarrhea, abdominal cramps, vomiting, muscle cramps, extreme anxiety, restlessness, tearing, runny nose, yawning, sweating and increased breathing or heart rate. Reducing the dose gradually under medical supervision can help prevent or decrease these withdrawal symptoms when this medication is no longer required for pain control.

Different methadone brands: There are several different manufacturers of methadone. It is important that you do not change brands of methadone. Recent reports have shown that some people using methadone for opioid replacement experience decreased effectiveness and withdrawal symptoms when the brand of methadone is switched.

Drowsiness/reduced alertness: Methadone may impair the mental or physical abilities you need for potentially hazardous tasks such as driving a car or operating machinery. You should avoid such activities until you are certain this medication does not have this effect on you.

Head injury: The side effects of methadone can make the effects of a head injury worse. If you have an acute head injury or other condition which increases intracranial pressure (pressure inside the head), discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking this medication.

Pain: It may become necessary to add pain relievers to methadone treatment if you are injured or have surgery. Do not increase your dose of methadone. Discuss with your doctor about temporary pain relief with another medication.

Prostate or urinary problems: Methadone can make symptoms of prostate or urinary tract problems worse. If you have prostate or urinary tract problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Serotonin toxicity: Severe reactions are possible when methadone is combined with other medications that act on serotonin, such as tricyclic antidepressants and serotonin reuptake inhibitors (medications used to treat depression). Symptoms of a reaction may include muscle rigidity and spasms, difficulty moving, or changes in mental state including delirium and agitation. Coma and death are possible.

If you are taking antidepressants, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Sleep apnea: Sleep apnea is a condition where you stop breathing for short periods while asleep. This can be caused or made worse by medications that slow breathing. Tell your doctor if you have a history of sleep apnea or if anyone notices that you periodically stop breathing while sleeping.

Thyroid function: This medication may make symptoms of an underactive thyroid gland worse. If you have thyroid disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pregnancy: Methadone crosses the placenta and may affect the unborn baby of a person who is taking methadone. Infants are often born smaller to people who have used methadone during pregnancy and they may also have long-term learning and behavioural difficulties. Infants born to people who have been taking methadone may experience life-threatening withdrawal symptoms after birth. This medication should not be used during pregnancy unless the benefits outweigh the risks to the unborn baby.

Breast-feeding: This medication passes into breast milk. If you are breast-feeding and are taking methadone, it may affect your baby. Babies exposed to methadone through breast milk are at risk of life-threatening breathing problems. If you have been breast-feeding and taking methadone, you should wean the baby slowly to prevent withdrawal effects in the infant. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children under 18 years old.

For a full list of interactions, use the Drug Interaction Checker available on the Drugs.com website.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.