Methadone use in the postoperative setting – Clinical practice point

MAY 2025

Methadone is a synthetic long-acting opioid analgesic which has traditionally been used in management of opioid addiction and treatment of chronic pain. It appears to be increasingly administered for postoperative acute pain management in major surgery. Whilst there are almost invariably multiple factors of concern, methadone has been implicated in postoperative morbidity and mortality of inadequately monitored patients in the ward environment where opioid induced ventilatory impairment has been the most likely cause of an adverse outcome. Opioid naïve patients are particularly at risk.

Methadone has a long and unpredictable half-life (mean 22 hr; range 4 -190 hr). It is not titratable in a short time frame such as in the postoperative care unit where opioid requirements vary and titration is warranted (Acute Pain Management: Scientific Evidence, 5th edition pp127-128). 

It is recognised that admitting all patients who have been administered intravenous methadone to a critical care area (intensive care unit, high-dependency unit) is impractical unless the surgery or patient comorbidities justify admission. Portable and wearable monitoring technologies are evolving but financial constraints remain the major obstacle to widespread adoption at this time.

With these limitations and risks in mind, the use of methadone as a single intraoperative dose for acute postoperative pain management should take into account the following considerations: 

1. Patient selection. Avoid use in patients with known or suspected sleep disordered breathing/obstructive sleep apnoea.
2. The dose administered should take into account the patient’s previous opioid tolerance and the level of postoperative observation and monitoring available.
3. Avoid further administration of methadone in the postoperative care unit/recovery unless a low mg/kg dose has been administered intraoperatively and close observation can be extended.
4. Postoperative monitoring. Perioperative use of methadone should be communicated to nursing staff and if not in a critical care environment there should be heightened monitoring for at least the night after surgery. Consideration should be given to clinical monitoring over this time similar to that required for intrathecal morphine.
5. Extreme caution is required when using with concomitant sedative medications. Avoid other long acting or modified release opioids.

Caution is required with use of methadone in the presence of regional blocks or local anaesthetic infusions.