Opiate analgesia: how central is a peripheral target?
Article Abstract:
Opiates are a class of drug administered to control pain. When given systemically, they are thought to affect the central nervous system, where they activate pathways that inhibit pain messages at the level of the spinal cord. Evidence presented in an article in the October 17, 1991 issue of The New England Journal of Medicine indicates that the opiate morphine exerts effects at peripheral sites as well. The opiate receptor, to which an opiate drug binds before exerting its pharmacological effect, is manufactured in cells (nociceptors) within the spinal cord (dorsal horn) and then transported toward the central nervous system and toward the periphery. Nociceptors can be activated by noxious stimuli or by innocuous stimuli that have become painful (sensitization). After surgery, much of the pain that is experienced results from sensitization. The peripheral actions of opiates are apparent only when tissue is injured or inflamed; physiological mechanisms possibly at work at these times are discussed. It is likely that opiates affect the levels of cyclic AMP in the nociceptor, a necessary part of the pathway that causes sensitization. This action could mean that these agents would provide more pain relief than nonsteroidal anti-inflammatory agents, which prevent prostaglandin synthesis. Peripheral administration of opioids would also prevent the side effects of gastrointestinal discomfort and renal complications associated with nonsteroidal anti-inflammatory drugs. Opiates may also decrease the peripheral manufacture of substances that cause pain during inflammation, such as substance P. While the endogenous ligand (chemical produced in the body that binds to the opiate receptor, activating it) for the peripheral opiate receptor has not been identified, evidence suggests it may be derived from lymphocytes (white blood cells). Therefore, treatments that reduce lymphocyte influx at an injured site may be effective. More research needs to be carried out concerning the role of peripheral opiates in pain control, as such treatments are likely to be important in clinical practice. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: The New England Journal of Medicine
Subject: Health
ISSN: 0028-4793
Year: 1991
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Analgesia for labor
Article Abstract:
Combined epidural and spinal analgesia controls the pain of labor during childbirth, but it is not yet clear how this technique affects the rate of cesarean section. A study comparing combined analgesia with epidural-only analgesia, techniques in which drugs are injected regionally around the spinal cord, found no difference in surgical deliveries. Researchers did not distinguish cesareans resulting from abnormal labor and those which might have related to early analgesia, nor did they include women who had no regional pain control during labor. The cesarean issue remains unresolved.
Publication Name: The New England Journal of Medicine
Subject: Health
ISSN: 0028-4793
Year: 1997
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Epidural analgesia compared with combined spinal-epidural analgesia during labor in nulliparous women
Article Abstract:
Combined spinal-epidural analgesia can provide effective pain control while permitting women to walk during labor. Epidural analgesia alone inhibits motor functions, confining most women to bed while they await delivery. Epidural and combined analgesia were compared in 761 women having their first baby. Both groups were satisfied with their pain relief and had similar rates of cesarean delivery. Spontaneous vaginal deliveries were more common in the combined analgesia group, as was increased itching and the use of supplemental pain medication.
Publication Name: The New England Journal of Medicine
Subject: Health
ISSN: 0028-4793
Year: 1997
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