Methadone maintenance therapy is a commonly used substitution treatment. Substances that activate receptors in the brain are called ‘agonists’. Methadone is a synthetic opioid agonist that affects the brain in the same way as morphine and heroin. Methadone is typically swallowed as a liquid. Because it is swallowed, the risks associated with injecting drug use are removed. When stabilised on methadone, a person is able to undertake usual life activities, including driving. Since the methadone is prescribed by a doctor, problems associated with controlling dosage and using the illegal market are less than with heroin. 

Methadone can be injected, and overdose is still possible. The evidence suggests, however, that methadone maintenance treatment substantially reduces the risk of death. It can also reduce heroin use, other criminal activity associated with the illegal market, and obstetric and fetal complications, and improve physical and psychological health. 

Because methadone is not effective for all heroin users, other drug therapies have been developed, including buprenorphine.

For more information, see Heroin.