Role of opioid analgesics in the treatment of chronic non-cancer pain

For more than 15 years opioids have been administered for chronic non-cancer pain. Refractory, chronic and extreme pain - even when associated with a non-cancerous disorder - should in many cases be considered 'malignant' on the basis of its quality and intensity. Clinical studies demonstrate that patients with pain of non-cancer origin may benefit from opioid therapy, if other therapeutic measures are ineffective. However, opioid therapy can fail to be effective and well tolerated if the choice of opioid is inappropriate, if dosages are inadequate or because of prescribing restrictions in many countries. Therefore, the lack of success of opioid therapy is largely due to factors other than pain unresponsiveness. Issues still to be resolved regarding long term opioid therapy concern whether non-cancer pain is an appropriate indication for opioids, long term effectiveness, the potential for physical dependence, abuse and addiction, and such adverse events as constipation and neuropsychiatric toxicity. For patients with chronic non-cancer pain it is important not only to reduce pain with opioid therapy, but also to improve performance. There is evidence showing both impaired and improved psychomotor performance during opioid therapy. The role of opioids in non-cancer pain will therefore remain controversial while there is a lack of controlled studies investigating their use in the long term treatment of this condition.