The two main prescription medications used in the UK to replace opioids are methadone and buprenorphine. Methadone is very well known. It might pose an excess risk of death from overdose at the start of treatment if the initial doses are too high or if there is illicit opioid use alongside the methadone. Buprenorphine is more modern than methadone but may be less effective in keeping patients in treatment* but studies show it has lower risk of death from overdose than methadone (or illicit opioids). Buprenorphine Buprenorphine (‘Subutex’ or ‘Suboxone’) is from the opioid family but it has both opioid-like effects (“agonist”) but also opioid blocking effects (“antagonist”). It is therefore an “agonist-antagonist” of opioid receptors in the brain and has been used in opioid drug misuse treatment since the 1970s, usually for heroin. Because of this mixed “agonist-antagonist” effect, buprenorphine use is associated with significantly lower risks of fatal overdose. When prescribed, it is administered under the tongue. Some users find its lack of euphoric effect frustrating, just like methadone, and there is often use of heroin ‘on top’. Methadone Methadone is prescribed to people who are misusing opioids, usually heroin. It is usually a green liquid that is taken orally, sometimes under the supervision of a pharmacist. Methadone is a manufactured ‘synthetic’ opioid that is almost exclusively used in the UK to treat opioid misuse. It is used as a substitute for the opioid (most commonly heroin) and hence is called “opioid substitute therapy” or “OST”. It has similar effects on the brain as heroin and other strong opioids but doesn’t give the same high . Therefore it is seen as a safer alternative to heroin and can reduce some of the massive harms from heroin misuse such as risks to the patient’s mental and physical health, damage to the patient’s family, and damage to society such as crime. It can either be prescribed as a long-term substitute or as a planned long term detox to come off opioids where the dose of methadone is slowly reduced over weeks, months, or years.