Materials and Methods: The present single-blind randomized clinical trial was conducted on 160 C-section candidates. The participants were randomly divided into four groups. When the fascia healed, the first group received 20 mL of 0.25% bupivacaine and the second group received 20 mL of 0.25% bupivacaine combined with subcutaneous adrenaline. In addition, both groups received 50 mL of intravenous normal saline. Further, the third group received subcutaneous bupivacaine and 50 mg/kg of magnesium sulfate and the fourth group received subcutaneous and intravenous normal saline as a placebo. The pain intensity was assessed 2, 6, 12, 18, and 24 hours after spinal anesthesia using the visual analogue scale (VAS) for pain. The dose of pethidine (as a standard analgesic) and hemodynamic parameters (i.e., heart rate [HR] and blood pressure [BP]) was recorded as well. The obtained data were then analyzed utilizing ANOVA, Tukey's HSD, and repeated measures ANOVA tests.

Results: The intensity of pain and the dose of pethidine decreased significantly in the combination of bupivacaine with magnesium compared to the other groups at all times (P < 0.001). However, diastolic BP significantly increased in the bupivacaine + adrenaline group in comparison with the other groups (P = 0.02).

Conclusions: Overall, bupivacaine combination with magnesium sulfate is suitable for controlling post-cesarean section pain.