Peripheral N-methyl-D-aspartate receptors as possible targets for chronic pain treatment

The effect of oral magnesium supplementation on acute non-specific low back pain: Prospective randomized clinical trial

OBJECTIVE

We aimed to investigate the effect of oral magnesium supplementation for acute low back pain.

METHODS

This is a three-arm, prospective randomized open label clinical trial, which included two hundred and forty patients. We based our sample size calculation assumptions on a recently published clinical trial, thus we enrolled 80 patients for each group. NSAID alone group included (400 mg etodolac twice a day), NSAID + mg group included NSAID - magnesium combination treatment (400 mg etodolac twice a day with 365 mg oral magnesium supplementation) and NSAID + paracetamol group included NSAID - paracetamol combination treatment (400 mg etodolac twice a day with 500 mg paracetamol twice a day). Follow-up visits after initiation of relevant treatment were performed at 4th and 10th days and outcome measures included pain (Visual analogue scale - VAS), mobility of lumbar spine and functional outcome (RMDQ).

RESULTS

Thirty-one patients were considered lost to follow-up or excluded due to use of other medications and final analysis was performed with 209 participants in three groups (71 patients in NSAID alone group, 68 patients in NSAID + mg group and 70 patients in NSAID + paracetamol group). NSAID + mg showed a significantly higher improvement in RMDQ and VAS scores at acute stage (at 4th day visit) compared to two other study groups However, there was no significant difference between three groups in terms of mean improvement of RMDQ, VAS scores and lumbar mobility between initial visit and 10-day.

CONCLUSION

Results of this study suggest that addition of magnesium to acute low-back pain treatment does not significantly improve final clinical outcomes.

LEVEL OF EVIDENCE

Level I, prospective randomized controlled study.

MAGnesium-oral supplementation to reduce PAin in patients with severe PERipheral arterial occlusive disease: the MAG-PAPER randomised clinical trial protocol

INTRODUCTION

Magnesium exerts analgaesic effects in several animal pain models, as well as in patients affected by acute postoperative pain and neuropathic chronic pain. There is no evidence that magnesium can modulate pain in patients with peripheral arterial occlusive disease (PAOD). We describe the protocol of a single-centre randomised double-blind clinical trial aimed at assessing the efficacy of oral magnesium supplementation in controlling severe pain in patients with advanced PAOD.

METHODS AND ANALYSIS

Adult patients affected by PAOD at stages III and IV of Lèriche-Fontaine classification, who are opioid-naïve, and who have been admitted to our Acute Pain Service for intractable pain, will be eligible. Patients will be randomised to the control group, treated with standard therapy (oxycodone and pregabalin) plus placebo for 2 weeks, or to the experimental group (standard therapy plus magnesium oxide). Patients will be evaluated on days 0, 2, 4, 6, 8, 12 and 14; the following information will being collected: daily oxycodone dose; average and maximum pain (Numerical Rating Scale); pain relief (Pain Relief Scale); characteristics of the pain (Neuropathic Pain Scale); impact of pain on the patient's daily activities (Brief Pain Inventory). The primary outcome will be oxycodone dosage needed to achieve satisfactory analgaesia on day 14. Secondary outcomes will be pain relief on day 2, time needed to achieve satisfactory analgaesia and time needed to achieve a pain reduction of 50%. A sample size calculation was performed for the primary outcome, which estimated a required sample size of 150 patients (75 per group).

ETHICS AND DISSEMINATION

Ethical approval of the study protocol has been obtained from Comitato Etico Provinciale di Brescia, Brescia, Italy. Trial results will be disseminated through scientific journal manuscripts and scientific conference presentations.

TRIAL REGISTRATION NUMBER

NCT02455726.

Gene silencing of NR2B-containing NMDA receptor by intrathecal injection of short hairpin RNA reduces formalin-induced nociception in C57BL/6 mouse

Spinal NR2B-containing N-methyl-D-aspartate receptors (NR2B) play a critical role in the formation of central sensitization and persistent pain. Previous studies show that gene silencing of the spinal NR2B subunit by small interfering RNA (siRNA) could alleviate nociception in animals. The siRNA is a 19- to 23-nt RNA duplex, which can be synthesized in vitro or derived from short hairpin RNAs (shRNAs). In the present study, we investigated whether intrathecal injection of shRNAs targeting NR2B (GRIN2B shRNA) could affect nociception on formalin-induced pain in mice. Our results showed that intrathecal injection of GRIN2B shRNA could decrease NR2B mRNA and protein expression levels and hence effectively relieve formalin-induced nociception in mice, suggesting that intrathecal delivery of GRIN2B shRNA can be an efficient way to silence the target gene and provide new insights into the treatment of chronic pain.