Addiction medicine
Opioid substitution therapy
Methadone and buprenorphine — Stabilising treatment for opioid dependence — reducing harm, illicit use and overdose deaths.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
What it is
Opioid substitution therapy provides a prescribed, longer-acting opioid medicine to people dependent on opioids, as the foundation of a treatment programme that includes psychological and social support. It reduces harm and supports recovery.
How it works
Methadone (a full opioid) and buprenorphine (a partial opioid) occupy opioid receptors steadily, preventing withdrawal and craving without the peaks and troughs of illicit use. Buprenorphine's partial action gives it a ceiling effect that makes overdose less likely, while methadone's long, smooth action provides stability.
In practice
In practice opioid substitution therapy with methadone or buprenorphine is one of the most effective harm-reduction treatments in medicine: it stabilises people dependent on opioids such as heroin, reduces illicit use, crime and the spread of blood-borne viruses, and lowers the risk of overdose death, especially when combined with psychosocial support. The highest-risk period is induction: starting methadone is dangerous because of its long action and accumulation, so doses are built up cautiously and often supervised, and the danger is greatest when tolerance is uncertain or when other sedatives or alcohol are involved. Buprenorphine is partially protective against overdose but must be started only once the person is in early withdrawal, or it will precipitate withdrawal. Methadone prolongs the QT interval, take-home naloxone is offered, and safe storage away from children is critical because even one dose can be fatal to an opioid-naïve person.
Examples
Practical use
How to take it & use it well
- Methadone and buprenorphine are used to treat opioid dependence as part of a supervised treatment programme with support and counselling.
- Treatment is usually started carefully and often supervised at a pharmacy at first, with doses adjusted to your response.
- Buprenorphine is taken as a tablet or film that dissolves under the tongue, and is usually started only once you are in mild withdrawal to avoid precipitating worse symptoms.
- Take your dose exactly as prescribed and do not top up with other opioids, alcohol or sedatives, as combining them can stop your breathing.
- Store your medicine locked away and out of reach of children, as even one dose can be fatal to a child or someone without tolerance.
- Carry and learn to use naloxone if provided, and make sure those around you know how to use it in an overdose.
Common uses
- Opioid (e.g. heroin) dependence — maintenance and harm reduction
- Supported, gradual detoxification
- Stabilisation alongside psychosocial treatment
Monitoring
- Stability, illicit use and engagement with support
- Supervised consumption during induction; QT/ECG where methadone risk factors exist
- Use of other sedatives/alcohol and overdose-risk review
Weighing it up
Advantages & disadvantages
Advantages
- Reduce illicit opioid use, cravings and withdrawal, and lower the risk of overdose and death.
- Help stabilise daily life, allowing engagement with work, family and treatment.
- Reduce harms linked to injecting, including infections such as hepatitis and HIV.
- Buprenorphine has a ceiling on its breathing effects, which can make it safer in overdose than full opioids.
Disadvantages
- Combining with alcohol, benzodiazepines or other opioids can dangerously suppress breathing.
- Methadone can affect the heart's rhythm, so the heart tracing may be checked.
- Buprenorphine can trigger withdrawal if started too soon after other opioids.
- Both are powerful opioids that must be stored securely to protect others, especially children.
- Treatment usually requires regular pharmacy visits, at least initially.
Key safety principles
What to watch for
- Induction is high-risk — methadone accumulates; build up cautiously, often supervised; danger rises with alcohol/sedatives.
- Start buprenorphine only in early withdrawal or it precipitates withdrawal; methadone prolongs the QT interval.
- Offer take-home naloxone; store extremely safely — a single dose can kill an opioid-naïve person, especially a child.
Key interactions
What to avoid or check alongside
- Benzodiazepines, alcohol and other sedatives combined with methadone or buprenorphine can cause fatal breathing suppression.
- Methadone with other medicines that prolong the heart's QT interval, such as some antibiotics, antipsychotics and antidepressants, raises the risk of a dangerous heart rhythm.
- Medicines that speed up the breakdown of methadone, such as some HIV medicines and rifampicin, can cause withdrawal, while inhibitors can raise levels.
- Other opioid painkillers on top of substitution therapy add overdose risk and should only be used under specialist advice.
Patient & carer advice
- Take it exactly as prescribed — never take extra or top up with other drugs or alcohol
- Store it locked away from children — one dose can be fatal to someone without tolerance
- Carry naloxone and know how to use it; engage with your support team
Use with
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Answers
Opioid substitution therapy: frequently asked questions
Why is buprenorphine started only when I am in withdrawal?
Buprenorphine attaches strongly to opioid receptors and can push off other opioids still in your body, causing sudden, severe withdrawal. Starting it once you are already in mild withdrawal avoids this.
Why must I store my medicine so carefully?
Methadone and buprenorphine are strong opioids. Even one dose can be fatal to a child or someone without opioid tolerance, so store it locked away, out of sight and reach, and never share it.
Is it dangerous to mix these with other drugs or alcohol?
Yes. Combining with alcohol, benzodiazepines or other opioids can seriously slow or stop your breathing and cause death. Always tell your prescriber about everything you take.
What is naloxone and why might I be given it?
Naloxone is an emergency medicine that can reverse an opioid overdose. People on substitution therapy and those around them may be supplied with it and trained to use it to save a life while waiting for help.
Why might methadone need a heart tracing?
Methadone can affect the heart's electrical rhythm, known as the QT interval. An ECG heart tracing may be done to check this is safe, especially at higher doses or with other medicines that affect the heart.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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