European journal of pain : EJP
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The use of opioid analgesics for long term management of chronic non-cancer pain is now an accepted, although still a controversial medical practice. In some well selected patients with long-lasting or recurrent pain, severe enough to markedly reduce their quality of life, and for whom no other more effective and less risky therapy is available, opioid analgesics may reduce intensity of pain, increase functioning and improve quality of life for prolonged periods. The type of pain and pain history of the patients do not predict reliably the chance of long term success or risk of complications from opioid therapy. ⋯ When a patient is managed by a multidisciplinary team, the compliance is better and risk of loss of control and complications are less than when a single doctor is managing the patient. The evidence base for this type of pain management is meagre because the needed randomized controlled trials, which ideally should last for several years, have not been performed. Therefore a number of national and international guidelines are being published, recommending experts' opinion on appropriate use and responsible follow-up of long term treatment with opioids for chronic non-cancer pain.
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Ligand-PET studies are attracting increasing interest in experimental and clinical research. As the most elaborated of PET techniques, ligand-PET allows the demonstration of receptor distributions, and thus, the delineation of neurochemical pathologies in the disease state. Recent developments are promising that ligand-PET will even allow to characterize dynamic and short-term changes in neurotransmission and will tremendously add to the understanding of neurophysiology on the receptor level. ⋯ One possible interpretation of these changes is that the PET-ligand might be displaced by endogenous opioidergic ligands. One major region, where this "ligand displacement" was observed, was the thalamus. These findings highlight the importance of the opioidergic system in pain processing and the power of ligand-PET to advance the understanding of pain.
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Opioids are powerful analgesics when used to treat acute pain and some forms of chronic pain. In addition, opioids can preempt some forms of central sensitization. Here we review evidence that opioids may also induce and perhaps reverse some forms of central sensitization.
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The human genome project has revealed data on genomic variation which may influence the pharmacological responses. In pain therapy, the genetic background influencing the efficacy of opioid therapy is of special interest. ⋯ Further candidate genes involved in pain perception, pain processing and pain management like opioid receptors, transporters and other targets of pharmacotherapy are under investigation. Aspects of genetic differences influencing efficacy, side effects and adverse outcome of pharmacotherapy will be of importance for future pain management.
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The clinical use of an intravenous opioid testing can help to predict whether opioids will be beneficial. The determination of individual opioid responsiveness justifies subsequent long-term opioid treatment and is generally recommended. An overview over current testing procedures is given with particular regard to choice of opioid, maximum dose, determination of endpoints and duration of testing and recovery. ⋯ Complete recovery after end of infusion was rapid with a reach of baseline conditions after 25 min in all patients. Thus the complete remifentanil testing procedure required at utmost 1 h. In conclusion, remifentanil testing offers a more rapid procedure allowing the routine use in an ambulatory setting.