What is the risk of interaction between opioids and monoamine oxidase inhibitors (MAOIs)?

This article considers the risks of interaction between opioids and monoamine oxidase inhibitors.

  • The use of MAOIs with opioids is contraindicated or cautioned by manufacturers. There is conflicting information in the literature about the degree of risk of an interaction.
  • Some opioid analgesics are associated with a risk of serotonin syndrome in combination with MAOIs due to their serotonergic properties. Other combinations may result in opioid toxicity due to CYP450 enzyme inhibition by the MAOI.
  • Any trials conducted in this field are not recent and measured different outcomes from those now included in the definition of serotonin syndrome. This means almost all information is based on case reports.
  • Given the widespread availability of several suitable alternative drugs, the combination of dextromethorphan, methadone, pethidine, tramadol, fentanyl or tapentadol with an MAOI should usually be avoided, including in the 14 day period following the withdrawal of an irreversible MAOI.
  • Morphine, codeine, oxycodone and buprenorphine are alternative opioids for patients receiving MAOIs, though starting at a low dose and titrating cautiously against clinical response is advised. Blood pressure and the signs and symptoms of CNS and respiratory depression should be monitored closely.