Methadone for opioid addiction
Until May 2018, practitioners needed exemption from Health Canada before they could prescribe, sell, provide or administer methadone.
Practitioners and pharmacists are still required to meet all other applicable provisions of the Narcotic Control Regulations, as well as the requirements established by their province or territory or the licensing authority These requirements may include additional courses or training.
How methadone works
Methadone is a potent full mu opioid agonist, as are morphine, oxycodone and other opioids. It has some unique pharmacological properties that make it useful in the treatment of opioid addiction:
- Because it has a slow onset and long duration of action, methadone does not cause intoxication or sedation in patients who are dependent on opioids if the dose is titrated carefully.
- Patients on an optimal dose of methadone have relief of withdrawal symptoms and cravings for 24 hours, and are able to think and function normally.
Methadone has a very long half-life (55 hours or longer in methadone-naive patients). This creates a gradual accumulation of methadone in the serum – after three days of dosing, the level is about 85 per cent of the final level. Clinically, this means that a methadone dose that is barely adequate on day 1 could cause a fatal overdose on day 5. Methadone physicians are trained to reduce overdose risk through strict dosing protocols.
Diverted methadone is likely the most important cause of methadone-related deaths (Madden & Shapiro, 2010). Methadone physicians attempt to reduce diversion by doing regular urine drug testing and gradually introducing take-home doses.
Candidates for methadone treatment
Methadone and buprenorphine-naloxone have very similar efficacy. Choosing between the two is a joint decision of the patient and the doctor.
Methadone may be preferred for patients who:
- have failed a course of buprenorphine or who are not eligible for public or private coverage and are not able to pay for buprenorphine
- are socially unstable
- use injection drugs
- have a long history of opioid addiction.
- Such patients can benefit from comprehensive methadone programs, which are highly structured and can offer counselling and medical services.
- Higher doses of methadone may be more effective than buprenorphine for treatment retention with patients who are addicted to heroin.