Protective effect of prior administration of magnesium on delayed hyperalgesia induced by fentanyl in rats

Pharmacological Interventions for Opioid-Induced Hyperalgesia: A Scoping Review of Preclinical Trials

BACKGROUND

Opioid analgesics are the most effective pharmacological agents for moderate and severe pain. However, opioid use has several limitations such as opioid-induced hyperalgesia (OIH), which refers to the increased pain sensitivity that occurs once analgesia wears off after opioid administration. Several pharmacological interventions have been suggested for OIH, but the current literature does not provide guidelines on which interventions are the most effective and whether they differ depending on the opioid that induces hyperalgesia. This scoping review aimed to identify and describe all the preclinical trials investigating pharmacological interventions for OIH caused by remifentanil, fentanyl, or morphine as the first step towards evaluating whether the most effective OIH interventions are different for different opioids.

METHODS

Electronic database searches were carried out in Embase, PubMed, and Web of Science. Detailed data extraction was conducted on the eligible trials.

RESULTS

72 trials were eligible for the review. Of these, 27 trials investigated remifentanil, 14 trials investigated fentanyl, and 31 trials investigated morphine. A total of 82 interventions were identified. The most studied interventions were ketamine (eight trials) and gabapentin (four trials). The majority of the interventions were studied in only one trial. The most common mechanism suggested for the interventions was inhibition of N-methyl-D-aspartate (NMDA) receptors.

CONCLUSION

This scoping review identified plenty of preclinical trials investigating pharmacological interventions for OIH. Using the current literature, it is not possible to directly compare the effectiveness of the interventions. Hence, to identify the most effective interventions for each opioid, the interventions must be indirectly compared in a meta-analysis.

Intravenous Magnesium - Lidocaine - Ketorolac Cocktail for Postoperative Opioid Resistant Pain: A Case Series of Novel Rescue Therapy

BACKGROUND

Severe postoperative pain is principally managed by opioids. While effective, opioids do not provide adequate relief in many patients and cause many side effects, including antinociceptive tolerance and opioid-induced hyperalgesia. To evaluate if a combination of intravenous Magnesium, Lidocaine, Ketorolac (MLK cocktail) is a useful rescue therapy through synergistic pharmacological mechanisms for acute pain relief. We present the intravenous combination of magnesium, lidocaine, and ketorolac (MLK cocktail) as a possible rescue for opioid insensitive severe post-operative pain.

MATERIALS AND METHODS

The principal settings were the post-operative care unit (PACU) and the surgical ward. We retrospectively analyzed the electronic medical record and anesthesia documents of 14 patients experiencing severe postoperative pain, >7/10 visual-analogue pain score (VAS), despite receiving at least 8 mg of intravenous morphine milligram equivalents (MME) after arrival in the LAC+USC Medical Center PACU between September 2012 and January 2013. The data reviewed included patients' demographics, disease etiology, surgical procedure, opioids received perioperatively, and visual-analogue pain scores before and after each analgesic received, and after the MLK cocktail. The a priori primary outcome and a posteriori secondary outcome of this study are mean visual-analogue pain score and morphine milligram equivalent dose administered per hour, respectively. The main tool evaluated has been VAS score.

RESULTS

In patients who failed to respond to opioid analgesics, administration of the MLK cocktail improved the VAS pain scores immediately from 9.4 ± 1.0 to 3.6 ± 3.5. The MLK cocktail also decreased the MME doses/hour in the immediate 12 hours postoperative period from 12.4 ± 5.6 to 1.1 ± 0.9.

CONCLUSION

In patients experiencing opioid-resistant severe postoperative pain, the magnesium, lidocaine, and ketorolac combination may be an effective nonopioid rescue therapy. Additionally, magnesium, lidocaine, and ketorolac may be utilized in cases complicated by either antinociceptive tolerance or opioid-induced hyperalgesia and can restore opioid responsiveness.

Magnesium sulphate attenuate remifentanil-induced postoperative hyperalgesia via regulating tyrosine phosphorylation of the NR2B subunit of the NMDA receptor in the spinal cord

BACKGROUND

Remifentanil induced hyperalgesia (RIH) is characterized by stimulation evoked pain including allodynia and thermal hyperalgesia after remifentanil infusion. N-methyl-D-aspartate (NMDA) receptor was reported to be involved in the progress of RIH. We hypothesized that intrathecal MgSO₄ could relieve hyperalgesia after remifentanil infusion via regulating phosphorylation of NMDA receptor NR₂B subunit activity in this study.

METHODS

Thirty two rats were randomly allocated into control group, model of RIH group, RIH plus 100ug MgSO₄ group, RIH plus 300ug MgSO₄ group. Mechanical and thermal hyperalgesia were tested at -24^th h, 2^nd h, 6^th h, 24^th h, 48^th h after remifentanil infusion. Following sacrifice of rats after the last behavioral test, we performed the western blot to detect the expression of spinal phosphorylated NMDA receptor NR₂B subunit (pNR₂B) in the L₄-L₅ segments.

RESULTS

Intrathecal MgSO₄ (100, 300 μg) dose-dependently reduced thermal and mechanical hyperalgesia from 2 h to 48 h after remifentanil infusion. Remifentanil infusion remarkably stimulated the expression of pNR₂B. Nevertheless, the increased amount of pNR₂B by RIH was dose-dependently suppressed by intrathecal infusion of MgSO₄ in rats.

CONCLUSIONS

Remifentanil induced hyperalgesia/allodynia could be ameliorated by Mg-mediated blockade targeting the NR₂B subunit in NMDA receptors.

A comparison of intrathecal magnesium and ketamine in attenuating remifentanil-induced hyperalgesia in rats

Background

Activation of NMDA receptors play an important role in the development of remifentanil-induced hyperalgesia. We hypothesized that in addition to ketamine, intrathecal MgSO₄ could also relieve thermal and mechanical hyperalgesia in rats.

Methods

Initially, 24 Sprague–Dawley rats were divided into control group, remifentanil group, surgical incision group and remifentanil combined with surgical incision group to create an experimental model. Subsequently, 40 rats were divided into control group, model group, model group plus 100 μg MgSO₄, 300 μg MgSO₄ and 10 μg ketamine respectively. Paw withdrawal mechanical thresholds and paw withdrawal thermal latency tests were performed at −24 h, 2 h, 6 h, 24 h, 48 h, 72 h and 7 day after the surgical procedure. After behavior assessment on the 7th day, remifentanil was given again to ascertain whether or not NMDA antagonists could suppress the re-exposure of remifentanil-induced hyperalgesia.

Results

Remifentanil administration plus surgical incision induced significant postoperative hyperalgesia, as indicated by decreased paw withdrawal mechanical thresholds and paw withdrawal thermal latency to mechanical and thermal stimulation. In addition to ketamine, intrathecal MgSO₄ (100, 300 μg) dose-dependently reduced remifentanil-induced mechanical and thermal hyperalgesia. Ketamine had less mechanical hyperalgesia in 6 h (p = 0.018), 24 h (p = 0.014) and 48 h (p = 0.011) than 300 μg MgSO₄. There was no difference in inhibiting thermal hyperalgesia between the group ketamine and group MgSO₄ (300 μg). The rats were given remifentanil again 7 days later after the first exposure of remifentanil. The hyperalgesic effect induced by re-exposure of remifentanil was not reversed in any groups of MgSO₄ or ketamine.

Conclusions

In addition to ketamine, intrathecal administration of MgSO₄ dose-dependently reduced remifentanil-induced hyperalgesia in a surgical incision mode. Re-exposure to remifentanil 1 week later again produced hyperalgesia, and this was not altered by the prior intrathecal treatments in any 4 groups treated with MgSO₄ or ketamine.

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-016-0235-9) contains supplementary material, which is available to authorized users.

Role of gabapentin in preventing fentanyl- and morphine-withdrawal-induced hyperalgesia in rats

PURPOSE

This study was undertaken to examine the effect of gabapentin for preventing hyperalgesia induced by morphine and fentanyl withdrawal in rats.

METHODS

To induce hyperalgesia, Sprague Dawley (SD) rats were subcutaneously injected with fentanyl four times at 15-min intervals (60 μg/kg per injection), resulting in total dose of 240 μg/kg over 1 h, and morphine 10 mg/kg twice daily for 7 days. The effect of gabapentin was detected with behavioral tail-flick and paw-withdrawal tests.

RESULTS

Drug termination produced significant decrease in antinociception thresholds (P < 0.05 vs. saline group), indicating that the rats became sensitive to thermal stimuli. In rats that received combined treatment with fentanyl/morphine and gabapentin (25/50 mg/kg), results demonstrated that there were no significant decreases in antinociception thresholds (vs. saline group) after opioid withdrawal. Gabapentin (50 mg/kg) could also prevent morphine tolerance. The 50% effective dose (ED50) value was 12.5 mg/kg in tail-flick and 13.6 mg/kg in paw-withdrawal tests.

CONCLUSIONS

The study showed that gabapentin can significantly prevented opioid-induced hyperalgesia (OIH) induced caused by fentanyl and morphine, suggesting a role for the addition of gabapentin in the perioperative period and during chronic pain treatment as an effective drug to prevent OIH.

The effects of intraoperative adenosine infusion on acute opioid tolerance and opioid induced hyperalgesia induced by remifentanil in adult patients undergoing tonsillectomy

Background

Adenosine has been shown to have a wide spectrum of unique pain-relieving effects in various clinical situations. The aim of this study was to investigate the effects of intraoperative adenosine infusion on acute opioid tolerance and opioid induced hyperalgesia induced by remifentanil in adult patients undergoing tonsillectomy.

Methods

For this study, ninety patients were randomly allocated into groups that receive either adenosine (adenosine group) or saline (remifentnail group) intravenously under remifentanil based anesthesia and saline (sevoflurane group) under sevoflurane anesthesia. The patients in adenosine group received adenosine at dose of 80 µg/kg/min, and those in remifentnail group and sevoflurane group received an equal volume of saline 10 minutes after the induction of anesthesia until the end of surgery. Intraoperative evaluation included time weighted mean remifentanil dose, and postoperative evaluations included degree of pain severity at 1, 6, 12, and 24 hours, time to first postoperative requirement, and analgesic dose required during 24 hours after operation.

Results

Time weighted mean remifentanil dose during intraoperative period in adenosine group was significantly lower than that of remifentnail group (P = 0.00). The first postoperative analgesic were required earlier in remifentanil group than sevoflurane group or adenosine group (P = 0.00). Pethidine requirement during 24 hours in sevoflurane group and adenosine group was significantly lower than that of remifentnail group (P = 0.00). The visual analog scale scores for pain in sevoflurane group and adenosine group were significantly lower than those of remifentnail group for 12 hours after operation (P = 0.00). Incidence of hypotension (P = 0.024) and number of ephedrine administered (P = 0.011) in adenosine group were significantly higher than those of sevoflurane group.

Conclusions

The above results suggest that intraoperative adenosine infusion prevent acute opioid tolerance and opioid induced hyperalgesia induced by remifentanil.