What are the adverse effects of methadone?
• Adverse effects include the following [RCGP, 2005c]: • Many people report a ‘clouding’ effect in the mind. Some people value this effect, whilst others do not. • People commonly complain of sore leg muscles, particularly when starting treatment or if taking suboptimal maintenance doses, and this may be due to ‘breakthrough’ withdrawal effects. • Other effects are common to opioids (e.g. nausea, vomiting, drowsiness, and constipation). Dry mouth, sweating, headache, amenorrhoea, and decreased libido may also occur. • Methadone has been reported to cause QT-interval prolongation and torsades de pointes (particularly at high doses of more than 100 mg/day) [ABPI Medicines Compendium, 2008]. People at increased risk of QT-interval prolongation (e.g. those with heart or liver disease, electrolyte abnormalities, concomitant treatment with CYP 3A4 inhibitors or medicines with the potential to cause QT-interval prolongation) and people requiring more than 100 mg methadone per day should be cl
