Background and Aim: Considering the side effects of high doses of opioids taken postoperatively for pain control, paracetamol and magnesium sulfate may be able to aid in pain control. This study assessed the effects of paracetamol and magnesium sulfate on the level of pain and opioid intake following orthognathic surgery.   
Materials and Methods: In this double-blind randomized clinical trial, patients scheduled for bimaxillary orthognathic surgery were randomly assigned to two groups of 25. Group 1 patients received 1 g infusion of intravenous acetaminophen (paracetamol) administered within 20 minutes while group 2 patients received 50 mg/kg magnesium sulfate infusion one hour prior to completion of surgery. The patients were asked to express their level of pain prior to discharge from the recovery, and every 4 hours for 12 hours using a visual analog scale (VAS). Patients with pain score > 5 at any time received 30 mg pethidine. The total received dosage of pethidine postoperatively was recorded and those that received pethidine were not included in pain score analysis. Data were analyzed by generalized estimating equation (GEE), and Mann-Whitney U, Chi-square, and t-tests.
Results: The pain score was not significantly different between the two groups at the time of recovery and 4 and 8 hours (P>0.05). The magnesium sulfate group had significantly lower pain score at 12 hours (P=0.009). The difference in pethidine dosage was not significant (P>0.05).
Conclusion: Both magnesium sulfate and paracetamol decreased postoperative pain and the need for opioid consumption, but magnesium sulfate was slightly more effective.