A clinical comparison of the two main opioid substitution treatments available on the NHS — how each works, who they suit, the pros and cons, and how to access them in the UK.
Opioid substitution therapy (OST) — also called opioid replacement therapy (ORT) — is the use of a prescribed, longer-acting opioid to stabilise someone dependent on a shorter-acting opioid like heroin, fentanyl, or prescription opioids. It is the most evidence-based treatment for opioid use disorder, reducing illicit drug use, drug-related deaths, and criminal activity, and improving physical and mental health outcomes.
The two main medications used in the UK are methadone (a full opioid agonist) and buprenorphine — most commonly prescribed as Suboxone (buprenorphine/naloxone) or Subutex (buprenorphine alone).
| Feature | Methadone | Suboxone (Buprenorphine/Naloxone) |
|---|---|---|
| Type | Full opioid agonist | Partial opioid agonist + antagonist |
| NHS availability | Widely available | Widely available |
| Form | Oral liquid (usually) | Sublingual film or tablet |
| Daily clinic visits | Usually required early on | Often less frequent |
| Overdose risk | Higher (full agonist) | Lower (ceiling effect) |
| Misuse potential | Higher | Lower (naloxone deters injection) |
| Withdrawal coverage | Excellent (high dependency) | Good (moderate dependency) |
| Tapering off | Slower, longer process | Easier to reduce doses |
| Drug interactions | More significant | Fewer |
| Pregnancy | First-line recommended | Used but methadone preferred |
Methadone is typically the first-line treatment for people with severe opioid dependency, particularly those who have been using heroin or fentanyl heavily for a long period. As a full agonist, it completely satisfies opioid receptors, effectively eliminating withdrawal symptoms and cravings.
Buprenorphine is a partial agonist — it activates opioid receptors but has a “ceiling effect,” meaning higher doses do not produce proportionally greater effects. This makes it significantly safer in overdose than methadone. The naloxone component deters injection by triggering withdrawal if injected.
Both methadone and Suboxone are available free on the NHS. To access OST:
You will have a clinical assessment to determine which medication and starting dose are appropriate for your level of dependency.
Yes. Buprenorphine (the active ingredient in Suboxone) is available on the NHS as part of opioid substitution therapy (OST). It is prescribed by drug treatment services and some GPs with specialist training. The naloxone component in Suboxone is added specifically to deter injection misuse. Access varies by area — your local drug treatment team can advise on what is available.
Neither is universally "better" — the right choice depends on your situation. Methadone is typically preferred for people with severe dependency, as it is a full opioid agonist and better controls strong withdrawal symptoms. Suboxone (buprenorphine/naloxone) is often preferred for people who want to taper off OST more quickly, as it is easier to reduce doses from. Both are evidence-based and NICE-approved.
Yes, but the switch requires careful management. You must be in mild to moderate withdrawal (not on a full dose of methadone) before starting buprenorphine, as starting it too early can trigger precipitated withdrawal — a sudden, severe withdrawal syndrome. The switch should always be managed by a prescriber experienced in opioid substitution therapy.
Treatment duration varies significantly. NICE guidelines recommend that treatment duration should be individualised — there is no fixed minimum or maximum. Some people remain on maintenance doses long-term as an ongoing treatment for addiction (similar to how people take antidepressants indefinitely). Others choose to gradually taper off. Research shows that premature discontinuation significantly increases relapse rates.
In the early stages of treatment, daily supervised consumption is standard for methadone — you attend a pharmacy each day to take your dose in front of a pharmacist. As your treatment stabilises, most people are granted takeaway doses (usually starting with 1–2 days, eventually up to 14 days' supply). Buprenorphine prescriptions often move to takeaway doses more quickly.