Methadone

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Target exams

Red flags

• The analgesic action of methadone lasts 4 to 8 hours but its plasma elimination half-life is 8 to 59 hours; its peak respiratory depressant effects occur later and persist longer than its peak analgesic effects.
• QT prolongation and torsades de pointes have occurred during methadone treatment, more commonly at doses above 200 mg/day.
• The potency of methadone relative to other opioids is non-linear and increases with increasing dose; deaths have occurred in opioid-tolerant patients during conversion.
• Methadone is a long-acting depressant (36 to 48 hours), whereas opioid reversal agents act for one to three hours: monitor until spontaneous respiration is reliably re-established.