gms | German Medical Science

The analgesic ladder guideline proposed by the World Health Organization has been shown to be effective in controlling cancer pain in more than 80 percent of patients, but the remaining still experience pain. Several strategies have been used to manage refractory cancer pain and opioid toxicity. Switching opioids, alternative routes of opioid administration, optimizing adjuvants, and invasive procedures are proposed treatments. Methadone can be a useful alternative in treating patients intolerant or unresponsive to other strong opioids. Although its main use has been in the maintenance treatment of opioid addicts, methadone has excellent analgesic effects, greater potency than previously assumed and low cost. Methadone, a lipophilic synthetic opioid with a high oral bio-availability, is known as a strong m- opioid and possibly a d-opioid receptor agonist. The analgetic effect is increased by the ability to block the NMDA-receptor-channel and the presynaptic re-uptake of serotonin. At present, methadone is viewed as a second-line opioid for chronic cancer pain. The titration can be difficult because the plasma half-life varies from 8-80h and accumulation is a potential problem for most patients. The fact that the methadone/morphine ratio differs widely -according to the opioid dose used previously and to different pain syndromes (somatic pain or neuropathic pain) - should be taken into careful consideration in order to avoid severe side effects during switchover. Methadone may be an important alternative for those who have side effects related to the use of other opioids because it has no known active metabolites. A particular role in neuropathic pain has been suggested. In addition, switching to methadone is more complex than with other opioids because of its increased potency in those patients who are opioid tolerant, particularly those who have been on higher doses of other opioids. Several guidelines of administration have been established. The complex and highly individual pharmacokinetics of methadone require that experienced clinicians take responsibility for initiating, titrating and monitoring this drug and should have a fundamental understanding of methadone's unique properties.