Risk-benefit assessment of opioids in chronic noncancer pain

Opioids have been accepted as appropriate treatment for acute and cancer pain, but their role in the management of chronic nonmalignant pain is the subject of much debate, mainly due to concerns about waning efficacy, the potential for neuropsychological impairment and the development of drug addiction. Controlled clinical trials demonstrated that opioids may be effective in both nociceptive and neuropathic noncancer pain, although the former responded more consistently than the latter. Gastrointestinal and CNS adverse effects were frequent in most studies. Observational studies have generated contradictory findings regarding efficacy and safety as well as the risk of drug addiction in patients with chronic noncancer pain receiving long term opioid therapy. However, they suggest that opioids may be effective in individual cases, whichever the pathophysiological mechanism of pain. Taken together, the available data indicate that the outcomes associated with opioid therapy vary markedly across patients experiencing chronic nonmalignant pain. The main consensus is that a subset of these patients may gain substantial benefit from opioid analgesics without requiring rapidly escalating doses or developing intolerable adverse effects or drug addiction. Prescribing guidelines have been developed to assist practitioners in selecting the appropriate patients and ensuring an acceptable risk : benefit ratio of opioid therapy. Finally, it must be emphasised that chronic pain is a complex entity wherein analgesics, including opioids, are only part of the treatment.