ABSTRACT
The use of opioids for the treatment of chronic non-cancer pain has become more widespread recently. Available data support the short-term use of opioids in clearly defined nociceptive and neuropathic pain states. Their use in ‘pathological’ pain states without a clear diagnosis, such as chronic low back pain, is more contentious. A decision to initiate opioid treatment in these conditions requires careful consideration of benefits and risks; the latter include not only commonly considered adverse effects such as constipation, but also opioid-induced hyperalgesia, abuse, addiction and diversion. Ideally, treatment goals should not only be relief of pain, but also improvement of function. Opioid treatment of chronic non-cancer pain requires informed consent by, and preferably a treatment contract with, the patient. Treatment should be initiated by a trial period with defined endpoints using slow-release or transdermal opioids. Ongoing management of the patient requires ideally a multi-disciplinary setting. Treatment should not be regarded as life-long and can be discontinued by tapering the dose.
The past half-century has seen a revolution in how we approach pain with the rethinking of the organisation of pain management. This began when John Bonica recognised the fragmentation of care that existed for many pain sufferers.1 He initiated the first interdisciplinary clinic for the assessment and treatment of patients with persistent pain. This was followed by Wall’s and Melzack’s description of the gate control theory of pain.2 Their theory linked the neurophysiological mechanisms of peripheral stimulation as well as the internal psychological activity. A surge of research followed which elucidated among others the mechanisms of opioid analgesia. Now it is understood that opioids such as morphine act by replacing a natural, endogenous substance (endorphins and enkephalins) in the descending pathways from brain to spinal cord that control the intensity of nociceptive tissue injury signals reaching the brain from the periphery.3
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