Rotation to methadone after opioid dose escalation: How should individualization of dosing occur?

Methadone is a synthetic opioid agonist and N-methyl-D-aspartate (NMDA) receptor antagonist that is being increasingly used in pain management, particularly for pain that is resistant to conventional opioids. We describe two patients with neurotoxic side effects on escalating doses of parenteral hydromorphone with uncontrolled cancer pain who were successfully converted to oral methadone at a dose much smaller than predicted. The phenomenon of increasing pain despite opioid dose escalation is discussed and the rationale for the use of methadone in this situation is described. While methadone is useful for patients with unremitting pain on another opioid, existing conversion regimens do not specifically take into account the setting of dose escalation. Clinical guidelines for rotation to methadone after dose escalation of the previous opioid are needed to avoid toxicity including respiratory depression. A possible conversion method for rotation to methadone for patients with escalating pain and opioid use is suggested.