Common opioids side effects:

• Constipation,

• Nausea, vomiting,

• Urinary retention (rarely at a distance from initiation),

• Myoclonus,

• Respiratory depression,

• Sedation,

• Cognitive impairment (including hallucinations, nightmares, agitation)

Methadone specific side effect:

QT prolongation with risk of torsade de pointes for high doses (>120mg/day). Caution for drug interaction with risk of QT allongement.