methadone

Last edited 05/2023 and last reviewed 05/2023

Methadone is a synthetic compound with pharmacologic action similar to that of morphine and heroin, almost equal in addiction liability.

The hydrochloride is used as an antitussive and analgesic and as a substitute narcotic in the management of opiate withdrawal, since it is longer acting than most opiates.

It is substituted for an abused opiate and then the dose is reduced.

• methadone is available as an oral solution (1 mg/ml), an oral concentrate (10 mg/ml), tablets or injectable ampoules
• methadone has a long elimination half-life (usually 20-37 hours), which allows for a once-daily dosing schedule
• methadone appears to have no serious long-term side effects associated with chronic administration (1)
• in the context of opioid dependence management, and using a methadone maintenance regimen, the drug does not have the pronounced narcotic effects seen with shorter-acting opioids such as illicit diamorphine
• interactions with other drugs
  • elimination of methadone is increased by some drugs including including rifampicin, phenytoin, phenobarbital and some antiviral drugs used in the treatment of HIV infection
  • rate of elimination is reduced by drugs such as fluvoxamine and fluoxetine

Conult the Summary of Product Characteristics before prescribing this drug.

Notes:

• methadone or buprenorphine should be offered as the first-line treatment in opioid detoxification. When deciding between these medications, healthcare professionals should take into account (2):
  • whether the service user is receiving maintenance treatment with methadone or buprenorphine; if so, opioid detoxification should normally be started with the same medication
  • the preference of the service user
• a review of 83 RCTs & 193 observational studies (total > 1 million participants) found, at timepoints beyond 1 month, retention in treatment was better for methadone vs buprenorphine (3)
  • also found evidence of reduced cocaine use, cravings, anxiety, and cardiac dysfunction, as well as increased treatment satisfaction among people receiving buprenorphine compared with methadone
  • evidence of reduced hospitalisation and alcohol use in people receiving methadone
  • note though that most comparisons were based on small numbers of studies

Reference:

1. NICE (January 2007).Methadone and buprenorphine for the management of opioid dependence
2. NICE (July 2007).Drug misuse - Opioid detoxification
3. Degenhardt L et al. Buprenorphine versus methadone for the treatment of opioid dependence: a systematic review and meta-analysis of randomised and observational studies. Lancet Psychiatry May 8th 2023.