Background:The present study was designed to evaluate the effectiveness of magnesium sulfate (MgSO4) in procedural sedation and analgesia (PSA) when combined with ketamine in patients with fractures in emergency departments and required short and painful emergency procedures.Materials and Methods:In this study, 100 patients with fractures and dislocations who were presented to the emergency departments and required PSA for short and painful emergency procedures were randomly allocated to groups of ketamine plus MgSO4 or ketamine alone. Train of four (TOF) stimulation pattern was assessed using nerve stimulator machine and compared between groups.Results:The mean age of studied patients was 46.9 ± 9.3 years old. 48% were male and 52% were female. No significant differences were noted between groups in demographic variables. The status of TOF, 2 min after the injection of ketamine (1.5 mg/kg), in both groups was similar. After the injection of the second dose of ketamine (1 mg/kg) the status of TOF in four patients in ketamine plus MgSO4 (0.45 mg/kg) group changed, it was three quarters but in ketamine group, the status of TOF in all patients was four quarters. The difference between groups was not statistically significant (P = 0.12).Conclusion:The findings revealed that for muscle relaxation during medical procedures in the emergency department, ketamine in combination with MgSO4 with this dose was not effective for muscle relaxation during procedures.