Clinical experience with the use of opioids for chronic, severe, non–malignant pain which is neuropathic in character suggests that there may be a sub–population of chronic severe pain patients who may clearly benefit from maintenance with opioid analgesics.
Many studies have shown that neuropathic pain is responsive to opioid treatments. It is suggested that fentanyl, e.g. Durogesic DTrans, may relieve intractable non–cancer neuropathic pain by its intrinsic analgesic effect. Most often, acute pain is nociceptive, whereas chronic severe pain can be nociceptive, neuropathic or mixed in origin. Opioids are the current standard of care for the treatment of severe nociceptive pain. The use of opioids to manage pain in patients with cancer is well accepted.
Figure of WHO analgesic ladder
The WHO stepwise algorithm for analgesic therapy based on pain severity reserves the use of opioid therapy for moderate and severe pain. The WHO algorithm has proven to be highly effective for the management of cancer pain. However, the use of opioids to treat patients with chronic non-cancer pain is controversial because of concerns about efficacy and safety, and the possibility of addiction or abuse. The oral route of drug administration is appropriate for patients receiving opioids, although the transdermal route is becoming more popular. For continuous chronic severe pain, opioids should be administered around-the-clock, and several long-acting formulations are available that require administration only once or twice daily.
Opioid doses should be titrated according to agent-specific schedules to maximise pain relief and maintain tolerability. Adverse effects include constipation, nausea and vomiting, sedation, cognitive impairment and respiratory depression. Tolerance to the analgesic and adverse effects, as well as physical dependence, which causes withdrawal symptoms upon discontinuance, may occur with opioid use. Estimates of addiction rates among patients with chronic non-cancer pain range from 3.2 to 18.9%. Successful pain treatment and symptom management is an attainable goal for the majority of patients with chronic severe pain.
Royal Pharmaceutical Society of Great Britain: News release regarding the prescribing of sustained release morphine preparations and opioid patches (Nov 2006)