Modulating pain in the periphery: gene-based therapies to enhance peripheral opioid analgesia: Bonica lecture, ASRA 2010.
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ABSTRACT:
SUBMITTER: Raja SN
PROVIDER: S-EPMC3288690 | biostudies-literature | 2012 Mar-Apr
REPOSITORIES: biostudies-literature
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Modulating pain in the periphery: gene-based therapies to enhance peripheral opioid analgesia: Bonica lecture, ASRA 2010.
Regional anesthesia and pain medicine 20120301 2
This article provides a brief overview of earlier work of our group on the peripheral signaling of pain, summarizes more recent studies on the role of opioids in chronic neuropathic pain, and speculates on the future of gene-based therapies as novel strategies to enhance the peripheral modulation of pain. Neurophysiologic and psychophysical studies have revealed features of primary afferent activity from somatic tissue that led to improved understanding of the physiology and pathophysiology of p ...[more]
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Project description:BACKGROUND:This is an updated version of the original Cochrane review published in Issue 4, 2006. Patients may control postoperative pain by self administration of intravenous opioids using devices designed for this purpose (patient controlled analgesia or PCA). A 1992 meta-analysis by Ballantyne et al found a strong patient preference for PCA over non-patient controlled analgesia, but disclosed no differences in analgesic consumption or length of postoperative hospital stay. Although Ballantyne's meta-analysis found that PCA did have a small but statistically significant benefit upon pain intensity, a 2001 review by Walder et al did not find statistically significant differences in pain intensity or pain relief between PCA and groups treated with non-patient controlled analgesia. OBJECTIVES:To evaluate the efficacy and safety of patient controlled intravenous opioid analgesia (termed PCA in this review) versus non-patient controlled opioid analgesia of as-needed opioid analgesia for postoperative pain relief. SEARCH METHODS:We ran the search for the previous review in November 2004. For this update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL 2014, Issue 12), MEDLINE (1966 to 28 January 2015), and EMBASE (1980 to 28 January 2015) for randomized controlled trials (RCTs) in any language, and reference lists of reviews and retrieved articles. SELECTION CRITERIA:We selected RCTs that assessed pain intensity as a primary or secondary outcome. These studies compared PCA without a continuous background infusion with non-patient controlled opioid analgesic regimens. We excluded studies that explicitly stated they involved patients with chronic pain. DATA COLLECTION AND ANALYSIS:Two review authors independently extracted data, which included demographic variables, type of surgery, interventions, efficacy, and adverse events. We graded each included study for methodological quality by assessing risk of bias and employed the GRADE approach to assess the overall quality of the evidence. We performed meta-analysis of outcomes that included pain intensity assessed by a 0 to 100 visual analog scale (VAS), opioid consumption, patient satisfaction, length of stay, and adverse events. MAIN RESULTS:Forty-nine studies with 1725 participants receiving PCA and 1687 participants assigned to a control group met the inclusion criteria. The original review included 55 studies with 2023 patients receiving PCA and 1838 patients assigned to a control group. There were fewer included studies in our updated review due to the revised exclusion criteria. For the primary outcome, participants receiving PCA had lower VAS pain intensity scores versus non-patient controlled analgesia over most time intervals, e.g., scores over 0 to 24 hours were nine points lower (95% confidence interval (CI) -13 to -5, moderate quality evidence) and over 0 to 48 hours were 10 points lower (95% CI -12 to -7, low quality evidence). Among the secondary outcomes, participants were more satisfied with PCA (81% versus 61%, P value = 0.002) and consumed higher amounts of opioids than controls (0 to 24 hours, 7 mg more of intravenous morphine equivalents, 95% CI 1 mg to 13 mg). Those receiving PCA had a higher incidence of pruritus (15% versus 8%, P value = 0.01) but had a similar incidence of other adverse events. There was no difference in the length of hospital stay. AUTHORS' CONCLUSIONS:Since the last version of this review, we have found new studies providing additional information. We reanalyzed the data but the results did not substantially alter any of our previously published conclusions. This review provides moderate to low quality evidence that PCA is an efficacious alternative to non-patient controlled systemic analgesia for postoperative pain control.
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Project description:PurposeAs previously reported, magnesium sulphate administered parenterally significantly increased an opioid antinociception in different kinds of pain. Since the typical form of magnesium salts are poorly and slowly absorbed from the gastrointestinal tract we examined whether their micronized form could increase opioids induced antinociception.MethodsIn behavioural studies on rats morphine, tramadol and oxycodone together with magnesium (lactate dihydrate, hydroaspartate, chloride) in micronized (particles of size D90 < 50 ?m) and conventional forms were used. Changes in pain thresholds were determined using mechanical stimuli. The intestinal absorption of two forms of magnesium lactate dihydrate (at the doses of 7.5 or 15 mg ions) in the porcine gut sac model were also compared.ResultsMicronized form of magnesium lactate dihydrate or hydroaspartate but not chloride (15 mg of magnesium ions kg-1) enhanced the analgesic activity of orally administered opioids, significantly faster and more effective in comparison to the conventional form of magnesium salts (about 40% for oxycodone administered together with a micronized form of magnesium hydroaspartate). Moreover, in vitro studies of transport across porcine intestines of magnesium ions showed that magnesium salts administered in micronized form were absorbed from the intestines to a greater extent than the normal form of magnesium salts.ConclusionsThe co-administration of micronized magnesium organic salts with opioids increased their synergetic analgesic effect. This may suggest an innovative approach to the treatment of pain in clinical practice.
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Project description:BACKGROUND:The current study used recombinant herpes simplex virus type I to increase expression of µ-opiate receptors and the opioid ligand preproenkephalin in peripheral nerve fibers in a mouse model of neuropathic pain. It was predicted that viral vector delivery of a combination of genes encoding the µ-opioid receptor and preproenkephalin would attenuate neuropathic pain and enhance opioid analgesia. The behavioral effects would be paralleled by changes in response properties of primary afferent neurons. METHODS:Recombinant herpes simplex virus type 1 containing cDNA sequences of the µ-opioid receptor, human preproenkephalin, a combination, or Escherichia coli lacZ gene marker (as a control) was used to investigate the role of peripheral opioids in neuropathic pain behaviors. RESULTS:Inoculation with the µ-opioid receptor viral vector (n = 13) reversed mechanical allodynia and thermal hyperalgesia and produced leftward shifts in loperamide (ED50 = 0.6?±?0.2?mg/kg vs. ED50 = 0.9?±?0.2?mg/kg for control group, n = 8, means ± SD) and morphine dose-response curves (ED50 = 0.3?±?0.5?mg/kg vs. ED50 = 1.1?±?0.1?mg/kg for control group). In µ-opioid receptor viral vector inoculated C-fibers, heat-evoked responses (n = 12) and ongoing spontaneous activity (n = 18) were decreased after morphine application. Inoculation with both µ-opioid receptor and preproenkephalin viral vectors did not alter mechanical and thermal responses. CONCLUSIONS:Increasing primary afferent expression of opioid receptors can decrease neuropathic pain-associated behaviors and increase systemic opioid analgesia through inhibition of peripheral afferent fiber activity.
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