Analgesic synergism between intrathecal morphine and cyclooxygenase-2 inhibitors in mice

Isobolographic Analysis of the Cytoprotective Effect of Dapsone and Cannabidiol Alone or Combination upon Oxygen-Glucose Deprivation/Reoxygenation Model in SH-SY5Y Cells

Oxidative stress and apoptosis cell death are critical secondary damage mechanisms that lead to losing neighboring healthy tissue after cerebral ischemia. This study aims to characterize the type of interaction between dapsone (DDS) and cannabidiol (CBD) and its cytoprotective effect in an in vitro model of oxygen and glucose deprivation for 6 h followed by 24 h of reoxygenation (OGD/R), using the SH-SY5Y cell line. For the combined concentrations, an isobolographic study was designed to determine the optimal concentration-response combinations. Cell viability was evaluated by measuring the lactate dehydrogenase (LDH) release and 3-[4, 5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assays. Also, the reactive oxygen species (ROS) and reduced glutathione (GSH) levels were analyzed as oxidative stress markers. Finally, caspase-3 activity was evaluated as a marker cell death by apoptosis. The results showed a decrease in cell viability, an increase in oxidant stress, and the activity of caspase-3 by the effect of OGD/R. Meanwhile, both DDS and CBD demonstrated antioxidant, antiapoptotic, and cytoprotective effects in a concentration-response manner. The isobolographic study indicated that the concentration of 2.5 µM of DDS plus 0.05 µM of CBD presented a synergistic effect so that in treatment, cell death due to OGD/R decreased. The findings indicate that DDS-CBD combined treatment may be a helpful therapy in cerebral ischemia with reperfusion.

The effect of adjuvant oral application of honey in the management of postoperative pain after tonsillectomy in adults: A pilot study

Objective

To analyze the effect of adjuvant oral application of honey for treating postoperative pain after tonsillectomy.

Design

Single centre prospective cohort study.

Setting

Two cohorts of patients after tonsillectomy.

Participants

56 patients treated with honey 8 times per day (honey group), 18 patients treated without honey (control group); baseline analgesia were non-steroidal anti-inflammatory drugs (NSAID) or coxibs; opioids were used as pro re nata (PRN) medication; mean age 34.4 ± 13.4 years; 36% women.

Main outcome measures

On first to fifth postoperative day, patients rated their pain using the validated questionnaire of the German-wide project Quality Improvement in Postoperative Pain Treatment (QUIPS) including a numeric rating scale (NRS, 0–10) for determination of patient's pain. QUIPS allows standardized assessment of patients' characteristics andpain-associated patient-reported outcomes (PROs). The influence of preoperative and postoperative parameters on patients' postoperative pain were estimated by univariate and multivariate statistical analysis.

Results

Average pain in activity in the control group was greater than 4 (NRS 4.4 ± 2.4) during the first five postoperative days, with a renewed increase in pain intensity on the fifth day (4.3 ± 2.5). In the honey group, the pain in activity decreased without any further pain increase and was only higher than 4 on the first three postoperative days (4.3 ± 2.1, all p>0.05). However; neither minimal nor maximal pain were significantly different between both groups on the first postoperative day (p = 0.217, p = 0.980). Over the five postoperative days, the minimal and maximal pain in the honey group decreased continuously and faster than in the control group. With regard to pain-related impairments on the first day, the honey group reported less pain-related sleep disturbance (p = 0.026), as well as significantly fewer episodes of postoperative oral bleeding (p = 0.028) than the control group. Patients without honey consumption had on the first and fifth postoperative day a higher risk of increased minimal pain (OR = -2.424, CI = -4.075 –-0.385). Gender was an independent factor for compliance of honey consumption on the second postoperative day (p = 0.037). Men had a lower probability for compliance of honey consumption (OR = -0.288, CI = -2.863 –-0.090).

Conclusion

There was a trend of reduced postoperative pain after oral honey application. Honey also seems to reduce pain-related impairments. The need for additional opioids on the first day could be reduced. A larger controlled trial is now needed to varify the effect of honey on pain after tonsillectomy.

Clinical trial registration number

German Clinical Trials Register DRKS00006153. The authors confirm that all ongoing and related trials for this drug/intervention are registered.

Sex differences in innate immunity and its impact on opioid pharmacology

Morphine has been and continues to be one of the most potent and widely used drugs for the treatment of pain. Clinical and animal models investigating sex differences in pain and analgesia demonstrate that morphine is a more potent analgesic in males than in females. In addition to binding to the neuronal μ-opioid receptor, morphine binds to the innate immune receptor toll-like receptor 4 (TLR4), located on glial cells. Activation of glial TLR4 initiates a neuroinflammatory response that directly opposes morphine analgesia. Females of many species have a more active immune system than males; however, few studies have investigated glial cells as a potential mechanism driving sexually dimorphic responses to morphine. This Mini-Review illustrates the involvement of glial cells in key processes underlying observed sex differences in morphine analgesia and suggests that targeting glia may improve current treatment strategies for pain. © 2016 Wiley Periodicals, Inc.

Analgesic potential of standardized methanol stem bark extract of Ficus platyphylla in mice: Mechanisms of action

ETHNOPHARMACOLOGICAL RELEVANCE

Extracts of the stem bark of Ficus platyphylla (FP) have been used in traditional the Nigerian medicine to treat psychoses, depression, epilepsy, pain and inflammation. Previous studies have revealed the analgesic and anti-inflammatory effects of FP in different assays including acetic acid-induced writhing, formalin-induced nociception, and albumin-induced oedema.

PURPOSE/METHODS

In this study, we assessed the effects of the standardised extract of FP on hot plate nociceptive threshold and vocalisation threshold in response to electrical stimulation of the tail root in order to confirm its acclaimed analgesic properties. We also investigated the molecular mechanisms underlying these effects, with the focus on opiate receptor binding and the key enzymes of eicosanoid biosynthesis, namely cyclooxygenase (COX) and 5-lipoxygenase (5-LO).

RESULTS

FP (i) increased the hot plate nociceptive threshold and vocalisation threshold. The increase in hot plate nociceptive threshold was detectable over a period of 30min whereas the increase in vocalisation threshold persisted over a period of 90min. (ii) FP showed an affinity for µ opiate receptors but not for δ or κ opiate receptors, and (iii) FP inhibited the activities of COX-2 and 5-LO but not of COX-1.

CONCLUSIONS

We provided evidence supporting the use of FP in Nigerian folk medicine for the treatment of different types of pain, and identified opioid and non-opioid targets. It is interesting to note that the dual inhibition of COX-2 and 5-LO appears favourable in terms of both efficacy and side effect profile.

Environmentally oriented models and methods for the evaluation of drug × drug interaction effects

This detailed review compares known and widely used methods for drug interaction estimation, some of which now have historical significance. Pharmaceutical application has been noted as far back as several thousand years ago. Relatively late in the 20th century, however, researchers became aware that their fate and metabolism, which still remain a great challenge for environmental analysts and risk assessors. For the patient's well-being, treatment based on the mixing of drugs has to be effective and should not cause any side effects (or side effects should not have a significant impact on health and mortality). Therefore, it is important to carefully examine drugs both individually and in combinations. It should be also stated that application form/way of entering the living organism is of great importance as well as the age and the place in the trophic system of the organism in order to eliminate harmful dosages in the case of infants' accidental intoxication.

Ellagic acid enhances the antinociceptive action of carbamazepine in the acetic acid writhing test with mice

CONTEXT

Ellagic acid (EA) produced antinociceptive and anti-inflammatory effects through the central and peripheral sites of action.

OBJECTIVE

The objective of the current study was to examine the functional interaction between ellagic acid and carbamazepine (CBZ) on pain.

MATERIALS AND METHODS

Fourteen groups of mice (8-10 each) were used in this study. Pain was induced by intraperitoneal acetic acid in mice (writhing test) and the functional interaction was analyzed using the isobolographic method. EA at doses 0.3, 1, 3, and 10 mg/kg and carbamazepine at doses 3, 10, 20, and 30 mg/kg, alone and also in combination (1/2, 1/4, and 1/8 of the drug's ED50) were intraperitoneally administered 30 min before acetic acid (0.6% v/v). Then, the abdominal writhes were counted during a 25-min period.

RESULTS

EA (0.3-10 mg/kg, i.p.) and CBZ (3-30 mg/kg, i.p.) inhibited the writhing response evoked by acetic acid. Fifty percent effective dose (ED50) values against this tonic pain were 1.02 mg/kg and 6.40 mg/kg for EA and CBZ, respectively. The antinociception induced by EA showed higher potency than that of carbamazepine. Co-administration of increasing fractional increments of ED50 values of EA and CBZ produced additive interaction against writhing responses, as revealed by isobolographic analysis.

DISCUSSION AND CONCLUSION

These results suggest that a combination of carbamazepine and ellagic acid may be a new strategy for the management of neuropathic pain such as what occurs in trigeminal neuralgia, since the use of carbamazepine is often limited by its adverse effects and by reduction of its analgesic effect through microsomal enzyme induction.

[Subarachnoid meloxicam does not inhibit the mechanical hypernociception on carrageenan test in rats]

BACKGROUND AND OBJECTIVE

Evaluate the antinociceptive effects of subarachnoid meloxicam on the mechanical hypernociception induced by carrageenan in rats.

METHODS

Randomized controlled trial. Eighteen adult male Wistar rats underwent a cannula implantation into the subarachnoid space and were randomly divided into two groups: Group I (GI) received saline solution 5μL, while Group II (GII) received meloxicam 30mg. The mechanical hypernociception was induced by intraplantar injection of carrageenan and evaluated using a digital analgesymeter every 30minutes during a 4 hour period. The results were recorded as the Δ withdrawal threshold (in g), calculated by subtracting the measurement value after

RESULTS

The Δ withdrawal threshold mean values were lower in the group of patients treated with meloxicam over all time points between 45 and 165minutes, however, there was no statistical significance, (p=0.835) for this difference.

CONCLUSION

Subarachnoid meloxicam at a dose of 30μg.animal(-1) did not suppress the mechanical hypernociception in a model of inflammatory pain induced by intraplantar administration of carrageenan in rats. The data suggest that other dosages should be investigated the drug effect is discarded.

Antinociceptive synergy between diclofenac and morphine after local injection into the inflamed site

BACKGROUND

Combinations of non-steroidal anti-inflammatory drugs with opioids are frequently used to reduce opioid doses required in the clinical management of acute pain. The present study was designed to evaluate the possible antinociceptive interaction between morphine and diclofenac at peripheral level in male rats.

METHODS

Drugs were chosen based on their efficacy in the treatment of this kind of pain and as representative drugs of their respective analgesic groups. For the formalin test, 50 μ of 1% formalin solution was injected subcutaneously into the right hind paw. The interaction between morphine and diclofenac was evaluated by using isobolographic analysis and interaction index. Drug interaction was examined by administering fixed-ratio combinations of morphine-diclofenac (1 : 1 and 3 : 1) of their respective ED30 fractions.

RESULTS

Diclofenac and morphine reduced flinching behavior in a dose-dependent manner during phase 2 but not phase 1 of the formalin test. Isobolographic analysis showed a synergistic interaction for the combination of morphine and diclofenac after local peripheral administration.

CONCLUSIONS

Data suggest that the combination of morphine with diclofenac at the site of injury is synergistic and could be useful in the treatment of wounds, bruises, rheumatisms and other painful peripheral conditions associated with an inflammatory process.

Parecoxib added to ropivacaine prolongs duration of axillary brachial plexus blockade and relieves postoperative pain

BACKGROUND

Cyclooxygenase (COX)-2 antagonist is widely used for intravenous postoperative pain relief. Recent studies reported COX-2 in the spinal dorsal horn could modulate spinal nociceptive processes. Epidural parecoxib in rats showed no neurotoxicity. These findings suggested applying a COX-2 antagonist directly to the central or peripheral nerve might provide better analgesia.

QUESTIONS/PURPOSES

We therefore determined: (1) whether the addition of parecoxib to ropivacaine injected locally on the nerve block affected the sensory and motor block times of the brachial plexus nerve block; and (2) whether parecoxib injected locally on the nerve or intravenously had a similar analgesic adjuvant effect.

METHODS

We conducted a randomized controlled trial from January 2009 to November 2010 with 150 patients scheduled for elective forearm surgery, using a multiple-nerve stimulation technique. Patients were randomly allocated into one of three groups: Group A (n = 50) received ropivacaine 0.25% alone on the brachial plexus nerve; Group B (n = 50) received ropivacaine together with 20 mg parecoxib locally on the nerve block; and Group C (n = 50) received 20 mg parecoxib intravenously. We recorded the duration of the sensory and motor blocks, and the most severe pain score during a 24-hour postoperative period.

RESULTS

Parecoxib added locally on the nerve block prolonged the motor and sensory block times compared with Group A. However, parecoxib injected intravenously had no such effect. Pain intensity scores in Group B were lower than those in Groups A and C.

CONCLUSIONS

Parecoxib added to ropivacaine locally on the nerve block prolonged the duration of the axillary brachial plexus blockade and relieved postoperative pain for patients having forearm orthopaedic surgery.

LEVEL OF EVIDENCE

Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The role of cyclo-oxygenase inhibitors in attenuating opioid-induced tolerance, hyperalgesia, and dependence

There is no denying that opioids are the most important analgesic drugs which are widely used in clinical situations. Still, prolonged administration of these drugs can cause to reduce their analgesic efficacy due to the development of tolerance. These drugs can also cause induction of hyperalgesia. In addition, long-term administration of opioids through reinforcing- and rewarding pathways of limbic system can result in expression of opioid dependence with the unintended consequences of opioid abuse/misuse and finally opioid addiction. As studies show, over-activity in cyclo-oxygenase pathways and production of prostaglandins due to long-term exposures of opioid have a critical role in the development of tolerance to antinociceptive effect of opioid, hyperalgesia, and opioid dependence. The present study aims at suggesting the hypothesis that through blending a non-steroid anti-inflammatory drug with opioid actively causes reduction in unwanted effects of opioid i.e. by inhibition of opioid-induced cyclo-oxygenase overactivity whereas it is well-known that the combination therapy via reducing opioid dosage reduces the unwanted effects.

The neurological safety of epidural parecoxib in rats

Epidural injection of cyclooxygenase-2 inhibitors has been suggested as a useful therapeutic modality in pain management in animal studies and clinical settings. Direct epidural administration of parecoxib, a highly selective cyclooxygenase-2 inhibitor, may have advantages over its parenteral administration regarding required dose, side effects, and efficacy. However, no animal studies have been performed to investigate the possible neurotoxicity of epidurally injected parecoxib. Therefore, the present study was performed to assess the neurotoxicity of epidurally injected parecoxib in rats. Rats (n=45) were randomly divided into three groups: normal saline group (group N, n=15), ethanol group (group E, n=15), and parecoxib group (group P, n=15). 0.3 mL of epidural parecoxib (6 mg) and the same volume of epidural ethanol or normal saline were injected into the epidural space. Neurologic assessment was performed 3, 7 and 21 days after the injection by pinch toe testing. Histologic changes were evaluated for vacuolation of the dorsal funiculus, chromatolytic changes of the motor neurons, neuritis, and meningeal inflammation. All rats in groups N and P showed normal response to pinch-toe testing and had a normal gait at each observation point. Histological examination showed no evidence suggestive of neuronal body or axonal lesions, gliosis, or myelin sheet damage in group N or P at any time. However, all rats in group E showed sensory-motor dysfunction, behavioral change, or histopathological abnormalities. No neurotoxicity on the spinal cord or abnormalities in sensorimotor function or behavior was noted in rats that received epidural parecoxib.

Antihypernociceptive synergy between ibuprofen, paracetamol and codeine in rats

We investigated the effects of intraperitoneal injections of a combination of two cyclo-oxygenase inhibitors, ibuprofen and paracetamol, with a weak opiate, codeine, on nociception in Sprague Dawley rats. Administration of paracetamol (11, 44, and 88 mg/kg), ibuprofen (8.75, 35, and 140 mg/kg) or codeine (0.44, 1.75, and 3.5mg/kg) alone caused a dose-dependent inhibition of reperfusion hypernociception. Administration of a combination of 0.44 mg/kg codeine+8.75 mg/kg ibuprofen+11 mg/kg paracetamol, drug doses that did not significantly reduce reperfusion hypernociception when administered individually or in pairs, abolished reperfusion hypernociception, such that the antihypernociceptive efficacy of the combination was approximately 2.5-fold greater than that of the sum of the antihypernociceptive efficacy of the individual drugs. Coordinated motor function, tested using a rotarod, was not impaired at the doses we used. Thus, we have demonstrated that codeine, paracetamol and ibuprofen act synergistically to induce antihypernociception in rats at doses which do not affect motor function.

Co-administration of ultra-low dose naloxone attenuates morphine tolerance in rats via attenuation of NMDA receptor neurotransmission and suppression of neuroinflammation in the spinal cords

Although mechanisms underlying ultra-low dose naloxone-induced analgesia have been proposed, possible interactions with glutamatergic transmission and glial cell activation have not been addressed. In the present study, we examined the effect of ultra-low dose naloxone on spinal glutamatergic transmission and glial cell activity in rats chronically infused with morphine. In male Wistar rats, intrathecal morphine infusion (15microg/h) for 5days induced (1) antinociceptive tolerance, (2) downregulation of glutamate transporters (GTs) GLT-1, GLAST, and EAAC1, (3) increasing of NMDA receptor (NMDAR) NR1 subunit expression and phosphorylation, (4) upregulation of protein kinase C gamma (PKCgamma) expression, and (5) glial cell activation. On day 5, morphine challenge (15microg/10microl) caused a significant increase in the concentration of the excitatory amino acids (EAAs) aspartate and glutamate in the spinal CSF dialysates of morphine-tolerant rats. Intrathecal co-infusion of ultra-low dose naloxone (15pg/h) with morphine attenuated tolerance development, reversed GTs expression, inhibited the NMDAR NR1 subunit expression and phosphorylation, and PKCgamma expression, inhibited glial cell activation, and suppressed the morphine-evoked EAAs release. These effects may result in preservation of the antinociceptive effect of acute morphine challenge in chronic morphine-infused rats. Ultra-low dose naloxone infusion alone did not produce an antinociceptive effect. These findings demonstrated that attenuation of glutamatergic transmission and neuroinflammation by ultra-low dose naloxone co-infusion preserves the lasting antinociceptive effect of morphine in rats chronically infused with morphine.

Synthesis and investigations of double-pharmacophore ligands for treatment of chronic and neuropathic pain

Acids 9a-f as possible bivalent ligands designed as a structural combination of opioid mu-agonist (Fentanyl) and NSAID (Indomethacin) activities and produced compounds which were tested as analgesics. The obtained series of compounds exhibits low affinity and activity both at opioid receptors and as cyclooxygenase (COX) inhibitors. One explanation of the weak opioid activity could be stereochemical peculiarities of these bivalent compounds which differ significantly from the fentanyl skeleton. The absence of significant COX inhibitory properties could be explained by the required substitution of an acyl fragment in the indomethacin structure for 4-piperidyl.

Lack of effect of naltrexone on the spinal synergism between morphine and non steroidal anti-inflammatory drugs

To enhance analgesia, the combinatorial use of analgesic drugs with proven efficacies is a widely-used strategy to reduce adverse side effects. The present study characterizes the antinociceptive interaction of intrathecal morphine co-administered with different NSAIDs using isobolographic analysis.Antinoceptive activity was evaluated using a model for acute visceral pain, the writhing test of mice. The possible involvement of opioid receptors in the mechanism of action of the intrathecal co-administration of morphine and NSAIDs was investigated using the non-selective receptor antagonist naltrexone. The study demonstrated a synergistic antinociception of intrathecal administered combinations of morphine with the following NSAIDs: diclofenac, ketoprofen, meloxicam, metamizol, naproxen, nimesulide, parecoxib and piroxicam. The supra additive effect was obtained with very low doses of each drug and it appeared to be independent of the COX-1 or COX-2 inhibition selectivity of each NSAID and was not significantly modified by intrathecal naltrexone. The findings of the present work suggest that the combination of opioids and NSAIDs has a direct action on spinal nociceptive processing, which may be achieved via mechanisms that are independent of the activation of opioid receptors. The ineffectiveness of naltrexone to reverse the analgesic activity of opioids + NSAIDs combinations indicates that other complex pain regulatory systems are involved in this effect.

Lipopolysaccharide and a social stressor influence behaviour, corticosterone and cytokine levels: divergent actions in cyclooxygenase-2 deficient mice and wild type controls

Administration of the endotoxin, lipopolysaccharide (LPS) diminished motor activity and increased plasma corticosterone as well as circulating levels of interleukin-1beta (IL-1beta), IL-6, tumor necrosis-factor-alpha (TNF-alpha) and IL-10. Among cyclooxygenase-2 (COX-2) knockout mice the behavioural, corticosterone and cytokine variations promoted by LPS were moderately (home cage activity, corticosterone, TNF-alpha) or largely (IL-6) reduced. However, if mice were exposed to a psychosocial stressor (social disruption associated with grouping mice with novel cage-mates after a period of isolation) coupled with LPS treatment, then the effects of the COX-2 deletion were absent, or there was a synergistic or additive elevation apparent (e.g., in the case of TNF-alpha, IL-6 and corticosterone). Evidently, COX-2 deletion may have either pro- or anti-inflammatory actions, depending upon the psychosocial context in which immune activation occurs.

Endogenous opiates and behavior: 2005

This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2005 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).