Analgesic Effect Evaluation of Methadone Associated With Morphine for Cancer Pain: Prospective Randomized Study

Opioids are the most important analgesics for the relief of cancer pain. In addition tolerance and hyperalgesia may ocurr as a consequence of treatment with these drugs. Medications for pain relief may also cause increased pain. NMDA receptor blockers may prevent or reduce the development of hyperalgesia. Methadone is a weak NMDA receptor antagonist and therefore its association could prevent hyperalgesia. The primary endpoint of the study was whether the administration of low dose methadone associated with morphine promotes better analgesic effect in patients with cancer pain, And secondarily to assess whether there is a reduction in the total dose of opioid needed for pain relief, and whether reduction of the opioid-related adverse effects occurs.