Opioids in cancer and chronic non-cancer pain therapy - indications and controversies

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Abstract
Indications for strong opioids for cancer-related pain as well as for chronic non-cancer pain are that non-opioid drugs, and other less risky therapies, fail and that the pain is opioid-sensitive. The WHO analgesic ladder principle continues to serve as an excellent educational tool in the efforts by WHO in collaboration with the World Federation of Societies of Anaesthesiologists (WFSA) and The International Association for the Study of Pain (IASP) to increase knowledge of pharmacological pain therapy and increase availability of essential opioid analgesics worldwide. Opioids differ in pharmacodynamics and pharmacokinetics, and patients have different pharmacogenetics and pain mechanisms. Sequential trials of the increasing numbers of available opioid drugs are therefore appropriate when oral morphine fails. Controversies continue concerning diagnosis and handling of opioid-insensitive pain in cancer and chronic non-cancer pain, opioid-induced neurotoxicities, risks of tolerance, addiction, pseudo-addiction, and methods for improving effectiveness and decreasing adverse effects of long-term opioid therapy, treating breakthrough pain with immediate release oral and transmucosal opioids. Consensus guidelines have recently been developed in the Nordic countries concerning the ethical practice of palliative sedation when opioids and other pain-relieving therapies fail in patients soon to die. Guidelines for long-term treatment with strong opioids of chronic non-cancer-related pain are also being developed in the Nordic countries, where very diverging traditions for the usage of such therapy still exist.