Switching from morphine to methadone to improve analgesia and tolerabilityin cancer patients: A prospective study

Purpose: To evaluate the clinical benefits of switching from morphine to or al methadone in patients who experience poor analgesia or adverse effects f rom morphine. Patients and Methods: Fifty-two consecutive cancer patients receiving oral morphine but with uncontrolled pain and/or moderate to severe avoid adverse effects were switched to oral methadone administered every 8 hours using d ifferent dose ratios. Intensity of pain and adverse effects were assessed d aily, and the symptom distress scare (DS) was calculated before and after s witching. Results: Data were analyzed for 50 patients. Switching was considered effec tive in 80% of the patients; results were achieved in an average of 3.65 da ys. In the 10 patients who switched to methadone because of uncontrolled pa in, a significant reduction in pain intensity (P < .005) and an average of a 33% increase in methadone doses necessary (P < .01) were found after an a verage of 3.5 days. DS significantly decreased from an average of 8.4 to 4. 5 (P < .0005), In the 32 patients switching because of uncontrolled pain an d morphine-related adverse effects, significant improvement was found in pa in intensity (P < .0005), nausea and vomiting (P < .03), constipation (P < .001), and drowsiness (P < .01), but a significant increase in the methadon e dose of an average of 20% (P < .004) was required. Conclusion: In most patients with cancer pain referred for poor pain contro l and/or adverse effects, switching to oral methadone is a valid therapeuti c option. In the clinical setting of poor pain control, higher doses of met hadone are necessary with respect to the equianalgesic calculated dose rati os previously published. (C) 2001 by American Society of Clinical Oncology.