Health Centres - Methadone
How does it work?
Methadone is a type of medicine called an opioid.
Opioids are painkillers such as codeine, morphine and diamorphine (heroin) that work by mimicking the action of naturally occurring pain-reducing chemicals called endorphins. Endorphins are found in the brain and spinal cord and reduce pain by combining with opioid receptors. However, opioids also act in the brain to produce a 'high' (feelings of euphoria) and hallucinations. They can be both physically and phsychologically addictive and people taking them long-term can become dependent on them.
Methadone is an opioid that is used mainly to wean people off their addiction to stronger opioids such as diamorphine (heroin). It is prescribed as a substitute for such drugs. By acting on the same opioid receptors as other opioids, methadone prevents the physical withdrawal symptoms that occur when these drugs are stopped. This prevents physical cravings for the drug. Over time, the dose of methadone is gradually reduced until it can be stopped completely.
Methadone is itself physically addictive, but is less psychologically addictive than heroin because it does not produce the same 'high' or sense of euphoria. This makes it easier to gradually reduce the methadone dose until no physical dependence remains.
Methadone substitution therapy for opioid addiction must be used in combination with other medical, social and psychological treatment.
Methadone, being an opioid, is also sometimes prescribed for the relief of moderate to severe pain.
Methadone can also be used to suppress dry cough in people with terminal illnesses such as lung cancer. Coughing is a reflex response to irritation of the airways. Methadone may be used to block the cough reflex in situations where the cough serves no purpose (e.g. dry persistent cough due to lung irritation in lung cancer). It suppresses cough by decreasing nerve messages from the brain that cause cough.
What is it used for?
- Treatment of addiction to opioids such as heroin
- Relief of moderate to severe pain
- Cough in terminal disease, eg lung cancer.
Warning!
- Your doctor may want to monitor your heartbeat with an ECG before you start treatment with this medicine and after your dose has been stabilised. Anyone taking more than 100mg methadone per day should have their heartbeat monitored with an ECG.
Use with caution in
- Elderly people
- Weak, ill or debilitated people
- Breathing problems, eg asthma
-
Constipation
-
Underactive thyroid gland
-
Enlarged prostate gland
- Decreased kidney function
- Decreased liver function
- Liver disease
- Heart disease
- History of problems with the electrical signals in the heart or abnormal heart beats (arrhythmias)
- Family history of sudden death
- Disturbance in the levels of electrolytes in the blood (eg low potassium or magnesium levels)
- People taking medicines that could increase the risk of abnormal heartbeats (see end of factsheet for more details).
Not to be used in
- Children
- Slow, shallow breathing (respiratory depression)
-
Chronic obstructive airways disease
- People having an asthma attack
- People with a head injury or raised pressure inside the skull
- People dependent on non-opioid drugs
- People who have taken a monoamine-oxidase inhibitor antidepressant (MAOI) in the last 14 days
- Women in labour.
This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
Pregnancy and breastfeeding
Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.
- This medicine should be used with caution during pregnancy and only if the expected benefit to the mother outweighs any potential risk to the baby. If used during the third trimester it may cause withdrawal symptoms in the baby after birth. It should not be used during labour. Seek medical advice from your doctor.
- This medicine passes into breast milk. It is recommended that mothers who need to take this medicine do not breastfeed their infants during treatment, as the methadone in the breast milk may cause sedation and withdrawal symptoms in the baby. Seek medical advice from your doctor.
Label warnings
- This medication may cause drowsiness. If affected do not drive or operate machinery. Avoid alcoholic drink.
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