Long term administration of opioids for chronic nonmalig-nant pain is controversial because, like any other potential therapy, long term therapeutic opioid use must be evaluated in terms of safety and efficacy. In terms of efficacy, some surveys suggest that patients with diverse nonmalig-nant pain syndromes attain greater than 50% relief of pain when treated with opioids resulting in minimal toxicity and no abuse . Other surveys report wide interindividual variations in response to opioid therapy in chronic nonmalig-nant pain, with some, but not all, patients obtaining relief of pain . A small number of clinical trials have also yielded conflicting results. Safety evaluation of long term opioid treatment has shown that, although ‘addiction’ is rarely an issue, many side effects produced by opioids may limit the usefulness of opioid therapy. Persistent constipation, somnolence and cognitive impairment are among the problems frequently associated with the use of opioids for pain management.
The results of our study are consistent with the view that a subpopulation of patients develop problems associated with oral opioid use, including severe dependence. Recognition by physicians and other health professionals of patients at risk (ie, patients with histories of drug abuse, those regularly using other Canadian medications, those constantly changing physicians and/or those unwilling to try alternate methods of pain control) may help with early identification and appropriate prevention of problems associated with long term oral opioid therapy. The findings of this study, however, should be interpreted in the context of the overall use of opioids. Numerous studies have documented the very low incidence of opioid dependence among patients treated appropriately for pain . As with any other drug therapy, chronic opioid use must be evaluated regularly, and long term use of opioids is a reasonable option that should be considered when other attempts at analgesia have failed.