Introduction & Objective: Magnesium is a NMDA receptor antagonist and a calcium channel blocker. The aim of the study is to evaluate the analgesic efficiency of preoperative magnesium sulfate infusion in patients undergoing elective cesarean surgery.

Materials & Methods: In a randomized double blind trial study approved by local ethics committee, 68 parturient who were admitted for elective cesarean section through spinal anesthesia were divided into two equal groups. Magnesium group (M) received IV magnesium sulfate 50 mg/kg as a bolus and then 10 mg/kg/h IV as continuous infusion at the time of surgery. The control group (S) received the same amount of isotonic saline. Both groups were completely monitored and the data about blood pressure, heart rate ,side effects and severity of pain (VAS) was recorded for 24 hours in the obstetric ward. The patients who had VAS = 4–6 received supp. Diclofenac Na (100 mg) and the patients who had VAS=7–10 received Diclofenac Na (75 mg) by intramuscular injection. The rate of diclofenac Na consumption was recorded for each patient.

Results: The pain scores in the magnesium group were significantly lower than the control group at 2 and 24 hours post operatively(P<0.05). Diclofenac dose consumption was also significantly lower in the magnesium group (137 ± 54 rather than 231± 67) and (P<0.005). Conclusion: IV magnesium sulfate administration during cesarean section in the parturients anesthetized intrathecally, decreases analgesic consumption after surgery and improves post-operative analgesia.