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Background: Intrathecal magnesium sulfate is now emerging as a safe and effective adjuvant for spinal anesthesia (SA). The aim of the present study was to compare the efficacy of two doses of intrathecal magnesium in parturients with pre-eclampsia. Methods: This prospective randomized double-blind study was conducted on 105 parturients undergoing elective cesarean section (CS) who were randomized into three groups of 35 each: Group C, M50, and M75. Group M50 and group M75 received 50 mg of 50% (0.1 ml) and 75 mg of 50% (0.15 ml) magnesium sulfate, respectively. All of the groups received 10 mg of 0.5% heavy bupivacaine with normal saline accordingly to make a total volume of 2.2 ml. The sensory and motor block characteristics, visual analogue scale (VAS) score, post-operative analgesic requirements, hemodynamic parameters, and adverse effects were compared. Results: The sensory and motor block characteristics were significantly delayed in group M75 compared to group M50 and the control group (P < 0.05). VAS scores were significantly high in the control group up to 6 h as compared to group M50 and group M75 (P < 0.05). The time to first rescue analgesia was significantly extended in group M75 (222.86 ± 12.502 min) as compared to group M50 (221.14 ± 13.671 min) and the control group (127.43 ± 11.464 min) ( P < 0.05) Conclusion: Intrathecal magnesium sulfate at doses of 50 mg and 75 mg in pre-eclamptic parturients undergoing elective CS results in prolonged duration of analgesia, decreased VAS scores and also delays the first rescue analgesic requirement with a favorable adverse effect profile in terms of decreased incidence of nausea and shivering.