Background: The quality and duration of sensory and motor block and decrease postoperative pain is important in the caesarean section and patient's content satisfaction. Opioids, clonidine, neostigmine and magnesium sulfate were added to local anesthetics in spinal anesthesia in trials to improve anesthetics performance.

Aim of the study: The aim of this study was to investigate the effect of adding 75 mg of magnesium sulfate on the duration of sensory block and duration of motor block.

Patients and methods: In a double-blind randomized clinical trial, ASA I or II, 64 (32 control and 32 experimental groups) pregnant women (at term) who were candidate for cesarean section with spinal anesthesia, were recruited in this study. They were collected from “Medical City Teaching Hospital” (October 2018 – January 2018).

Each experimental woman received 12.5 mg (2.5 ml) of hyperbaric bupivacaine (0.5%) and 0.5 ml (75 mg) magnesium sulfate (15%), while controls received same does of hyperbaric bupivacaine and 0.5 ml of distilled water.

Response to treatment was assessed as onset of anesthesia, time of end of surgery, duration of sensory block and time of complete recovery.

Results: Results revealed that the duration of analgesia (sensory blockade) and the duration of motor blockade manifested a statistically significant increase in experimental as compared to their controls (control = 116.41 ± 12.47, experimental = 159.75 ± 10.56, control = 180.76 ± 11.83, experimental = 240 ± 9.46 minutes respectively).

Conclusion: The addition of 75 mg of magnesium sulfate to hyperbaric bupivacaine in spinal anesthesia for cesarean section had significantly increased the duration of postoperative analgesia and prolonged the sensory and motor blockade without significant apparent maternal or fetal side effects.