Medication Information Leaflet

There are certain restrictions in the supply of Methadone, as it is not available in community/retail pharmacies and is only available in selected healthcare institutions via prescription from in-house doctors. Please check with your healthcare provider if they are able to supply it.

What is this medication for?

Methadone is used under medical supervision and counselling to treat opium addiction in elderly people and opioid addiction in pregnant women. It helps to reduce withdrawal symptoms in patients being treated for heroin or opioid addiction.

Methadone may also be used for reducing severe pain.

Methadone may be used for other conditions. Check with your healthcare professional if you are unsure why you are given this medication.

Methadone is a controlled drug in Singapore.

How should I take/use this medication?

If you think you or someone else may have taken an overdose of Methadone, call 995 at once for emergency help.

  • Methadone may be taken with or without food.
  • Take your medication according to the instructions stated on the medication label.
  • Do not stop taking or adjust the dose of this medication without checking with your doctor.
  • Do check with your doctor on how long you will have to be on this medication.
  • You may experience unpleasant effects if you suddenly stop taking methadone on your own, such as:
    • Sweating and chills (shivers)
    • Muscle pain
    • Dilated (wide open) pupils
    • Irritability
    • Difficulty sleeping
  • To reduce the chances of developing such effects, your doctor may gradually reduce the dose of methadone before stopping it completely.

What should I do if I forget to take/use this medication?

  • If you forget to take a dose, take it as soon as you remember. However, if more than half of the time to the next dose has passed, skip the missed dose and take the next dose at your usual timing.
  • For example, for a medication to be taken two times daily at 8am and 8pm, and you missed your first dose at 8am, skip the first dose if it is after 2pm, and take your second dose at the usual timing at 8pm. Do not take two doses to make up for the missed dose.
  • Inform your doctor if you miss 3 days or more of your regular prescribed dose as it may reduce the effectiveness of your treatment or put you at an increased risk of side-effects when restarting the medication.

What precautions should I take?

Inform your healthcare professional if:

  • You are allergic to this medication or any of the other ingredients of this medication
  • You are taking methadone for any other medical reasons
  • You are pregnant, planning to become pregnant, or breastfeeding. If you are pregnant and/or breastfeeding, your doctor would have discussed the potential benefits and side-effects with you and should you have further questions or concerns, do consult your doctor.
  • You are taking any other medications (including those that can be bought without a prescription), supplements, traditional Chinese medicine and herbal products. Some of them may affect how this medication works or cause serious drug interactions.
  • You are taking or have taken medication for depression or Parkinson’s disease within the past 2 weeks
  • You have or have ever had:
    • Other drug allergies
    • Kidney, liver, bowel, prostrate, gallbladder or thyroid disease
    • Medical conditions such as seizures (fits), brain disease, head injury or breathing problems

What are some common side-effects of this medication?

The mentioned side effects generally affect up to 10% of patients.

  • Drowsiness or feeling tired
    • Avoid driving or taking part in activities that require concentration
    • Discuss with your doctor if you can take your medication at a different time of the day
  • Nausea, vomiting or loss of appetite
    • Take the medication with or after food
    • Take small but more frequent meals, and avoid fatty or spicy food
  • Constipation
    • Drink more water (if you do not have any fluid restriction), eat more high-fibre foods, and exercise regularly
    • Speak to your doctor or pharmacist if you need medication to help with your constipation
  • Dizziness
    • Get up slowly from a sitting or lying down position

Most of the side effects listed here will improve with time. Speak with your doctor if any of them continues, worsens or affects your daily life.

What are some rare but serious side-effects that I need to seek medical advice immediately?

The symptoms of a drug allergy include one or more of the following:

  • Swollen face/eyes/lips/tongue
  • Difficulty in breathing
  • Itchy skin rashes over your whole body

Rarely this medication may cause:

  • Severe dizziness or passing out
  • Fast heartbeat (tachycardia) or chest pain
  • Fast or irregular heartbeat, fainting episodes (signs and symptoms of an abnormal heart beating rhythm (prolonged QTc interval))
  • Big changes in ability to think clearly and logically
  • Feeling extremely tired or weak
  • Seizures (fits)
  • Very hard stools
  • Shortness of breath, huge weight gain, swelling in the arms or legs

If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.

What food or medication should I avoid when I take this medication?

Avoid drinking alcohol while taking methadone as it can cause excessive sleepiness.

Avoid grapefruit juice/products while taking Methadone, as the amount of Methadone in the body may be increased.

How should I store this medication?

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children.

How should I throw away this medication safely?

Proper disposal of controlled drugs is essential to prevent misuse, abuse and accidental consumption. Pack this medication into a bag and return it to the pharmacy for disposal.


Please take note that the above is not a complete list of all possible side effects. If you have any concerns about your medication or if you have other side effects that you think are caused by this medication, please consult your doctor or pharmacist.

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

Last updated on Mar 2023

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