Articles: chronic.
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Hydromorphone is a micro receptor agonist opioid. According to WHO recommendations, hydromorphone is to be classified in step III of pain therapy. An oral formulation with a prolonged duration of action of 12 hours has been evaluated only recently. The controlled release capsule is especially suited for the regular twice a day administration in cases of severe and persistent pain. The oral formulation of hydromorphone increases the number of opioid analgesics available for pain therapy in step III. Hydromorphone is recommended when morphine fails to produce sufficient pain relief (despite increase of doses) or causes intolerable side effects (despite treatment of symptoms). In principle, no differences in efficacy of morphine and hydromorphone are to be expected. However, clinical experience shows that changing one opioid analgesic to another one can improve the treatment of patients so that hydromorphone may replace another opioid analgesic to which a patient fails to respond well or develops side effects. The dose of hydromorphone equivalent to 2 times 30 mg controlled release morphine is about 2 times 4 mg. The values for the absorption, bioavailability and maximum plasma concentration after the administration of controlled release hydromorphone every 12 hours -of three times the dose- are equivalent to those of an immediate release tablet given every 4 hours. In several open label and controlled studies, hydromorphone proved to be of good efficacy in the treatment of acute and persistent pain, especially in patients with severe cancer pain. With regard to the incidence of side effects, no significant differences between morphine and hydromorphone could be established. In general, the side effects of hydromorphone are typical for opioid analgesics. ⋯ In conclusion, controlled release hydromorphone seems to be well suited for the control of severe chronic pain when given twice daily.
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Disregarding pain resulting from vitamin deficiency, an analgesic effect seems to be exerted only by vitamin B1 (thiamine), vitamin B6 (pyridoxines), and vitamin B12 (cobalamine), particularly when the three are given in combination. The analgesic effect is attributed to an increased availability and/or effectiveness of noradrenaline and 5-hydroxytryptamine acting as inhibitory transmitters in the nociceptive system. In animal experiments, high doses of these vitamins administered alone or in combination inhibited nociceptive behavior and depressed the nociceptive activity evoked in single neurons of the dorsal horn of the spinal cord and in the thalamus. ⋯ The use of high doses of vitamin B6 may be limited by a neurotoxic effect. The effectiveness of B vitamins in depressing chronic pain has not been established. It would be interesting to know if the B vitamins are of use as adjuvants in the treatment of tumor pain.
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Peripheral nerve injury may lead to neuropathic pain that has been considered unresponsive to opioids. In animal models of neuropathic pain, there are previous data of both increased and decreased effect of opioids, but only limited information of the long-term effects of opioid treatment on the development of the symptoms of neuropathy. The possibility of preventing the development of signs of neuropathy with either a single pre-injury injection or chronic postinjury administration of morphine was studied in rats with unilateral peripheral neuropathy due to tight ligation of the L5 and L6 spinal nerves. ⋯ No autotomy, signs of distress, altered social behaviour or morphine withdrawal was seen in any of the rats. The fact that neuropathic pain-like symptoms were not attenuated by any of the treatments studied could indicate that neither premedication nor postoperative pain management with systemic morphine is effective in preventing postoperative neuropathic pain. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.
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Basic research indicates that systemic local-anaesthetic-type drugs that block sodium channels are effective in pain due to nerve damage. These drugs were first used as analgesics in the 1950s and they are still commonly used to try to relieve neuropathic pain and incident pain caused by cancer. As they are potentially toxic, these drugs should not be used without proven effectiveness. ⋯ Only minor dose-related adverse effects were reported in the 85 patients given mexiletine 225-750 mg. Local-anaesthetic-type drugs are effective in pain due to nerve damage, but there is little or no evidence to support their use in cancer-related pain. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.
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The transdermal therapeutic system (TTS) for fentanyl is a drug-delivery system for use in patients with chronic pain who require an opioid analgesic. A multicentre, randomized, double-blind, placebo-controlled study was performed to evaluate the efficacy and safety of TTS-fentanyl as an analgesic for chronic cancer pain. One hundred and thirty-eight patients entered a 15-day dose-titration period, followed by a 9-day double-blind period (95 patients) with TTS-fentanyl or placebo. ⋯ Due to an unexpectedly high placebo response it was not possible to demonstrate fentanyl to be statistically superior to placebo. This may reflect the practical difficulties of performing clinical trials in cancer patients with great inter-individual variability. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.