Introduction: Magnesium has been used as an adjuvant to local anesthetic via epidural route to 
augment the quality of block and prolong postoperative analgesia. Aim of the work: To assess and 
compare the effect of adding three different doses of magnesium sulfate to bupivacaine in epidural 
anesthesia in patients scheduled for lower abdominal surgeries on onset of sensory and motor block, 
duration of block, number of top up doses, duration of analgesia, early postoperative pain and to 
evaluate any possible side effects. Patients and Methods: This study was controlled, randomized, 
prospective and double blinded. A total of 120 patients, ASA grade I-II, aged between 18 and 64 were 
scheduled for lower abdominal surgery. All patients were assessed clinically after taking medical 
history and through physical examination and investigated for exclusion of any contraindications, 
complete blood picture (CBC), Prothrombin time and concentration, liver function, renal function and 
resting ECG was done. The patients were randomly allocated into four equal groups according to the 
dose of magnesium sulfate injected in the epidural space, 30 patients in each. Each group received 
total volume of 15 ml which may be (14 ml bupivacaine + 1 ml saline), (14 ml bupivacaine + 50 mg 
MgSO4 in 1 ml saline), (14 ml bupivacaine + 75 mg MgSO4 in 1 ml saline) or (14 ml bupivacaine + 
100 mg MgSO4 in 1 ml saline). The onset and duration of sensory and motor block, duration of 
postoperative analgesia, postoperative visual analogue scale and any side effect were noted. Results: 
Onset of sensory and motor block was faster in (100 mg group) than other groups. Duration of 
sensory and motor block and time to first analgesic request were longer in 100 mg group than others.
Discussion: Epidural magnesium sulfate (100mg) significantly prolonged postoperative analgesia 
compared to 50mg, 75mg and bupivacaine alone. we recommend: Usage of magnesium sulfate as 
adjuvant to epidural anesthesia in a dose of (100 mg) for earlier onset and prolonged postoperative 
analgesia.