Pitfalls of opioid rotation: substituting another opioid for methadone in patients with cancer pain.

The successful use of methadone in cancer pain has been supported by numerous case reports and clinical studies. Methadone is usually used as a second or third line opioid medication. As the use of methadone increases we are facing the challenge of converting methadone to other opioids as part of sequential opioid trials. Data on the equianalgesic ratios for the substitution of other opioids for methadone are lacking. We present prospective data on 13 consecutive rotations from methadone to a different opioid. The opioid rotation was followed by escalation of pain and/or severe dysphoria, not controlled by a rapid increase in the dose of the second opioid, in 12 of the 13 patients. Only one patient was successfully maintained on the second opioid after the discontinuation of methadone, while 12 patients required a switch back to methadone. We conclude that opioid rotation from methadone to another opioid is often complicated by worsening pain and dysphoria. These symptoms may not improve despite upward titration of the second opioid. A uniformly accepted conversion ratio for substituting methadone with another opioid is currently not available. More data on the rotation from methadone to other opioids are needed.