Postoperative pain is a significant factor that impacts the surgical outcome and course of treatment. The major goal of postoperative pain management is to reduce the dose of medications and consequently the incidence of side effects, while ensuring sufficient pain relief. Postoperative pain relief leads to earlier mobilization, shortened hospital staying, reduced hospital costs, and increased patient satisfaction ^.

Opioids are the most frequently used analgesics for postoperative pain. However, they have their own limitations and adverse effects including constipation, pruritis, altered mental state and respiratory depression. Hence, there is need of certain adjuvant analgesics which reduce the requirement of opioids without compromising the post operative pain relief and recovery

Magnesium (Mg) is a positively charged divalent cation which has minimal side effects and has long been utilized in medical practice as an anticonvulsant or antiarrhythmic drug .  Being an NMDA receptor antagonist, magnesium has the potential to be employed as an adjuvant analgesic. Furthermore, it also disrupts the entry of calcium into the cell and produces central analgesic action.  At the peripheral level, it inhibits the release of catecholamine from the sympathetic neurons, resulting in a reduction of peripheral nociception and the stress reaction after surgery. 

There are studies which evaluate the role of magnesium as an adjuvant analgesic. Most of them were carried out in patients who were undergoing surgery under general anaesthesia. Relatively few studies have been conducted on the effects of magnesium sulphate administration during spinal anaesthesia ^{[1, 2,7]}. Furthermore, most of them evaluated the role of perioperative IV magnesium in reducing post operative pain. To the best of our knowledge, none of the studies evaluate the efficacy of IV MgSO4 in intraoperative and post operative period under spinal anaesthesia. Peng at el also confirmed in his metanalysis that there is need of future research that evaluates the effect of time of delivery of IV magnesium sulphate on analgesia  Hence, the current study is planned to evaluate and compare the efficacy and safety of preoperative, intraoperative and post operative IV magnesium sulphate under spinal anesthesia.