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Efficacy-Based Perspective to Overcome Reduced Opioid Analgesia of Advanced Painful Diabetic Neuropathy in Rats.

ABSTRACT: Reduction of the opioid analgesia in diabetic neuropathic pain (DNP) results from ?-opioid receptor (MOR) reserve reduction. Herein, we examined the antinociceptive and antiallodynic actions of a novel opioid agonist 14-O-methymorphine-6-O-sulfate (14-O-MeM6SU), fentanyl and morphine in rats with streptozocin-evoked DNP of 9-12 weeks following their systemic administration. The antinociceptive dose-response curve of morphine but not of 14-O-MeM6SU or fentanyl showed a significant right-shift in diabetic compared to non-diabetic rats. Only 14-O-MeM6SU produced antiallodynic effects in doses matching antinociceptive doses obtained in non-diabetic rats. Co-administered naloxone methiodide (NAL-M), a peripherally acting opioid receptor antagonist failed to alter the antiallodynic effect of test compounds, indicating the contribution of central opioid receptors. Reduction in spinal MOR binding sites and loss in MOR immunoreactivity of nerve terminals in the spinal cord and dorsal root ganglia in diabetic rats were observed. G-protein coupling assay revealed low efficacy character for morphine and high efficacy character for 14-O-MeM6SU or fentanyl at spinal or supraspinal levels (E _max values). Furthermore, at the spinal level only 14-O-MeM6SU showed equal efficacy in G-protein activation in tissues of diabetic- and non-diabetic animals. Altogether, the reduction of spinal opioid receptors concomitant with reduced analgesic effect of morphine may be circumvented by using high efficacy opioids, which provide superior analgesia over morphine. In conclusion, the reduction in the analgesic action of opioids in DNP might be a consequence of MOR reduction, particularly in the spinal cord. Therefore, developing opioids of high efficacy might provide analgesia exceeding that of currently available opioids.

SUBMITTER: Balogh M

PROVIDER: S-EPMC6465774 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Efficacy-Based Perspective to Overcome Reduced Opioid Analgesia of Advanced Painful Diabetic Neuropathy in Rats.

Balogh Mihály M Zádor Ferenc F Zádori Zoltán S ZS Shaqura Mohammed M Király Kornél K Mohammadzadeh Amir A Varga Bence B Lázár Bernadette B Mousa Shaaban A SA Hosztafi Sándor S Riba Pál P Benyhe Sándor S Gyires Klára K Schäfer Michael M Fürst Susanna S Al-Khrasani Mahmoud M

Frontiers in pharmacology 20190409

Reduction of the opioid analgesia in diabetic neuropathic pain (DNP) results from μ-opioid receptor (MOR) reserve reduction. Herein, we examined the antinociceptive and antiallodynic actions of a novel opioid agonist 14-O-methymorphine-6-O-sulfate (14-O-MeM6SU), fentanyl and morphine in rats with streptozocin-evoked DNP of 9-12 weeks following their systemic administration. The antinociceptive dose-response curve of morphine but not of 14-O-MeM6SU or fentanyl showed a ...[more]

PMID: 31024314

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Project description:BackgroundPainful diabetic peripheral neuropathy (PDPN) affects up to 26% of patients with diabetes mellitus, with major impacts on their general health and well-being. Most available drugs fail to deliver acceptable pain reduction in the majority of patients and are often poorly tolerated. NRD.E1 is a novel product that has shown anti-nociceptive preclinical effects and good tolerability in healthy volunteer studies.MethodsThis phase 2a, randomized, dose-finding, Proof of Concept study enrolled patients with PDPN of ≥3 months duration. After at least one treatment-free week (WO week), 88 patients entered a 1-week single-blind (SB)-placebo run-in period, followed by 3 weeks' double-blind (DB) treatment, during which they received NRD.E1 at 10, 40 or 150 mg/day or placebo.ResultsThe primary endpoint (change from SB-placebo run-in week to week 3 in weekly mean of daily average numerical rating scale [NRS] pain intensity) showed clinically relevant placebo-corrected treatment effect pain reductions at 40 mg and 150 mg/day of 0.82 (95% CI: 0.07, 1.58, p = 0.034) and 0.66 (95% CI: -0.03, 1.35; p = 0.061) NRS points, respectively, though did not meet the pre-specified value of p = 0.016 required due to multiplicity. An additional post hoc endpoint looking at the change from WO baseline to week 3 in weekly mean of daily average NRS showed the placebo-corrected treatment effect was 1.46 (95% CI: 0.26, 2.66), and 1.20 (95% CI: 0.10, 2.29) NRS points, respectively. Secondary and post hoc analyses of NRS pain data (including 30 & 50% responder rate and NNT), sleep interference, Short-form McGill pain questionnaire (especially pain intensity assessed on Visual Analogue Scale), Patient's and Clinician's Global Impression of Change showed effects consistent with the primary findings. NRD.E1 was well tolerated, with only headache reported in more than two patients and more frequently on NRD.E1 than placebo.ConclusionsThe data suggest that NRD.E1 potentially represents a novel non-opioid therapeutic option for patients with PDPN, with at least similar efficacy and better tolerability than available therapies, justifying its further evaluation in larger-scale confirmatory studies.SignificanceNRD.E1 is a novel non-opioid therapeutic which is being developed for the treatment of PDPN. In this randomized, controlled, dose-finding, Proof of Concept study, NRD.E1 induced a clinically relevant pain reduction and it was well tolerated. Available data suggest that NRD.E1 has at least similar efficacy and better tolerability than the currently available therapies, potentially offering a promising new therapeutic option to patients with PDPN and possibly other neuropathic pain indications.

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Efficacy-Based Perspective to Overcome Reduced Opioid Analgesia of Advanced Painful Diabetic Neuropathy in Rats.

Publications

Efficacy-Based Perspective to Overcome Reduced Opioid Analgesia of Advanced Painful Diabetic Neuropathy in Rats.

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