Methadone hydrochloride

How it works

It is a full agonist at the mu-opioid receptor with a long half-life, providing sustained suppression of withdrawal and craving, and additionally has NMDA-receptor antagonist activity.

Prescribing in practice

• Methadone carries a high risk of fatal respiratory depression, particularly during initiation, dose titration and in opioid-naive individuals, and overdose risk is increased by concomitant alcohol, benzodiazepines or other CNS depressants.
• It prolongs the QT interval and can cause torsade de pointes, so an ECG and review of cardiac risk factors and interacting medicines is advised.
• Supervised consumption is commonly required at the start of treatment because of accumulation risk from its long half-life.

Monitoring

Monitor for sedation and respiratory depression during titration, assess QT interval where cardiac risk factors exist, and review treatment response regularly.

Counselling the patient

• Do not drink alcohol or take other sedating medicines with methadone, as the combination can be fatal.
• Keep this medicine locked away and out of reach of children, as even one dose can be fatal to a child.
• Do not take extra doses if you feel a dose is not holding you; contact your service instead.

Evidence & guidelines

Methadone maintenance is an established evidence-based treatment for opioid dependence supported by NICE guidance, and the MHRA has highlighted the risks of QT prolongation and respiratory depression.