Introduction: In recent years, Magnesium sulfate was used for acute pain relief following several types of surgeries. In current study for the first time, we compared the effects of this drug on acute pain following open repair of inguinal hernia with that of bupivacaine.

Materials and methods: In current randomized clinical trial, there were 80 patients with unilateral inguinal hernia assigned to two equal groups: bupivacaine (B) and magnesium sulfate (M). Open repair was performed. Group B received tramadol 0.5% (5 cc) in 5 mL 0.9% normal saline and group M received 10 cc of magnesium sulfate 20, both as a local wound infiltration before the wound closure.  At first postoperative day, pain intensity, analgesic consumption, and incidence of side effects were measured and compared.

Results: The pain intensity was the same at hours 1 and 3; however, was significantly lower in group B in hours 6, 12 and 24 (p<0.05). The number of morphine requirements was significantly lower in group B (0.9±0.9 vs. 1.6±1; p=0.001). PONV was observed in 9 and 15 patients in group B and S, respectively, and the difference was not significant (p=0.143).

Conclusion: The local infiltration of bupivacaine provides better pain relief and is associated with lower analgesic consumption following open repair of unilateral inguinal hernia compared to magnesium sulfate.