Intravenous Magnesium Sulfate for Acute Nontraumatic Headache in the Emergency Department.

STUDY OBJECTIVE: The aim of this study was to determine whether intravenous MgSO4 offers additional analgesic benefit when administered simultaneously with paracetamol in emergency department patients presenting with acute nontraumatic headache.

METHODS: In this randomized, double-blind, placebo-controlled clinical trial, adults presenting with acute nontraumatic headache received 1 g of oral paracetamol prior to randomization, then were assigned to receive either 2 g intravenous MgSO4 in 150 mL saline solution or placebo 150 mL saline solution alone, infused more than 30 minutes. The primary outcome was the treatment success, defined as a ≥30% reduction in the numerical rating s̶cale score at 30 minutes. Secondary outcomes were the need for rescue analgesia, patient satisfaction, and adverse events.

RESULTS: We included 506 patients in MgSO4 group and 522 in placebo group. Success was more frequent in the MgSO4 (78.9 %) versus placebo group (65.1%) (difference 13.8%; 95% confidence interval [CI] 8 to 19); however, all timed numerical rating s̶cale differences were below the 1.3-point accepted threshold for clinical importance. In the MgSO4 group, rescue analgesia was required less frequently (7.1% versus 15.3%; difference -8.2%; 95% CI -12 to -4.3), patient satisfaction was greater (91.7% versus 85.1%; difference 6.6; 95% CI 2.7 to 10), and adverse events were more frequent (15.4% versus 11.1%; difference 4.3; 95% CI 0.1 to 8.4).

CONCLUSION: Adding intravenous MgSO4 to paracetamol achieved more frequent success in treating acute nontraumatic headache, but at levels below accepted thresholds for clinical importance. MgSO4 was associated with less frequent rescue analgesia and a modest increase in mild side effects.