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

Purpose: To evaluate the clinical benefits of switching from morphine to oral methadone in patients who experience poor analgesia or adverse effects from morphine. Patients and Methods: Fifty-two consecutive cancer patients receiving oral morphine but with uncontrolled pain and/or moderate to severe opioid adverse effects were switched to oral methadone administered every 8 hours using different dose ratios. Intensity of pain and adverse effects were assessed daily, and the symptom distress score (DS) was calculated before and after switching. Results: Data were analyzed for 50 patients. Switching was considered effective in 80% of the patients; results were achieved in an average of 3.65 days. In the 10 patients who switched to methadone because of uncontrolled pain, 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 average 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 and morphine-related adverse effects, significant improvement was found in pain intensity (P <.0005), nausea and vomiting (P <.03), constipation (P <.001), and drowsiness (P <.01), but a significant increase in the methadone dose of an average of 20% (P <.004) was required. Conclusion: In most patients with cancer pain referred for poor pain control and/or adverse effects, switching to oral methadone is a valid therapeutic option. In the clinical setting of poor pain control, higher doses of methadone are necessary with respect to the equianalgesic calculated dose ratios previously published.