Magnesium Sulfate Potentiates Morphine Antinociception at the Spinal Level

Abstract

Magnesium sulfate potentiates morphine analgesia when coadministered intrathecally in normal rats, and in an animal model of mechanical allodynia after a surgical incision. These results suggest that intrathecal administration of magnesium sulfate may be a useful adjunct to spinal morphine analgesia.

A comparison of intra-articular magnesium and/or morphine with bupivacaine for postoperative analgesia after arthroscopic knee surgery

“…In another study, by McCarthy and colleagues [22], the addition of magnesium sulfate to morphine in an intrathecal infusion provided better analgesia than morphine alone in normal rats. Kroin et al [23] demonstrated that acute bolus dosing of intrathecal magnesium sulfate produced dose-dependent potentiation of the antinociceptive effect of morphine to noxious thermal stimulation in normal rats and mechanical stimulation at an incisional pain site; these investigators reported that magnesium could potentiate opioid analgesic effects by both central and peripheral mechanisms. In human investigations, Unlugene et al [24] reported that the addition of magnesium or ketamine to morphine for IV patientcontrolled analgesia led to a signifi cantly lower consumption of morphine.…”

Could adding magnesium as adjuvant to ropivacaine in caudal anaesthesia improve postoperative pain control?

“…Intravenous magnesium was used for posttonsillectomy pain in children and reported to have no effect on analgesia [18]. It was demonstrated that the ineffectiveness of magnesium in intravenous applications may be due to its inability to form effective cerebrospinal fluid concentrations because of inadequate penetration through the blood-brain barrier [13]. For this object, Buvanendran et al [20] used magnesium intrathecally and demonstrated that 50 mg intrathecal use of magnesium prolonged analgesia in adults.…”

“…However, i.v. magnesium, even high doses, is associated with limited passage across the blood-brain barrier [13].…”

Effects of adding magnesium to bupivacaine and fentanyl for spinal anesthesia in knee arthroscopy

“…administered Mg prolonged spinal opioid analgesia both in rats and humans [15,16]. The addition of i.t.…”