What is it?

Opioid Substitution Therapy (OST) is defined as the administration of a prescribed (daily) dosage of opioid medicines to patients with opioid dependence problems. Today, drugs used in substitution therapy in the UK are guided by NICE (National Institute for Care and Health Excellence), which endorses methadone and buprenorphine, with morphine and its derivatives and heroin being prescribed far less frequently. The ‘daily’ above is interesting and probably the single largest factor discouraging people from entering and remaining in treatment.

Some GPs already have agreements with local specialist agencies that they will not prescribe for users, or if they do, it will be in conjunction with specialist drug services. Consequently, the range of treatment options may be reduced in some areas to specific medications.

Opioid substitution therapy programmes are effective in substantially reducing illicit opiate use, HIV risk behaviours, death from overdose, poor health, criminal activity, and seek to lessen financial pressures and other stresses on drug users and their families.

How is it prescribed?
Methadone is usually prescribed once-daily, with the initial daily dose of 20–30 mg that is later increased.

Most methadone patients receive 60–120 mg of methadone per 24 hours, but some need higher doses (if a patient is a ‘quick metaboliser’). Methadone patients for the most part stabilize at a ‘ceiling’ dose and do not need the increases associated with other opioids.


Methadone’s advantages against other substitution drugs are its low cost, single-daily use and good oral bio-availability.

Recognised side effects include sweating, constipation and reduced libido. Some find its lack of euphoric effect frustrating and use ‘on top’.

Buprenorphine (as ‘Subutex’ and particularly as ‘Suboxone’) is an agonist-antagonist of opioid receptors that has been used in drug dependence treatment since 1978.

Buprenorphine use is also associated with much lower risks of deadly overdose, as increasing the daily dose above 24-32 mg seems to have little effect. It is administered sublingually. Its pharmacological characteristics make it possible to use it once a day or every other day.


Benefits of OST
Benefits for the patients of OST and entering treatment include the following:

  • Improved social functioning.
  • Increased possibilities for monitoring, testing and treatment of HIV, Hepatitis B and C.
  • Reduced overdose mortality.
  • Discontinued or reduced incidence of injecting.
  • Reduced risks of HIV and Hepatitis.
  • Improved physical and mental health (with competent treatment).