The use of intravenous magnesium sulfate to treat acute nontraumatic headaches has potential benefits, despite concerns over the efficacy of this treatment, according to a review article published in Headache.

Intravenous magnesium sulfate is an alternative to opioid-based drug treatment for acute headaches in emergency department visits; however, questions exist about its efficacy and benefits as an analgesic in acute headaches. This study is a review of the effects of intravenous magnesium sulfate compared with placebo and alternative treatments.

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The authors of the review compared the effectiveness of intravenous magnesium sulfate as an analgesic in acute headaches to placebo, corticosteroids, dopamine antagonists, ergot alkaloids, nonsteroidal anti-inflammatory drugs, triptans, or usual care. They systematically examined prospective, randomized clinical trials to determine if these treatments lower the rate of headache recurrence after 24 hours. To be included in the review, patients had to be at least 18 years old and to have been treated in an emergency department or outpatient acute care treatment center; magnesium sulfate had to have been administered intravenously. Of 4018 potential references, 7 met the inclusion criteria. The 7 studies (with a total of 545 participants) were assessed for potential sources of bias and one study did show potential bias due to the small sample size. Pain levels were assessed at baseline and 15, 30, 60, 90, or 120 minutes after treatment.

Magnesium sulfate showed some improvement in pain 1 hour after treatment. Pain intensity was measured at 30 minutes in 5 studies, and all of them reported no difference in pain between magnesium sulfate and placebo. At 60 minutes, magnesium sulfate was superior to an ergot alkaloid, systemic corticosteroid plus dopamine antagonist, and placebo. Another study showed superior pain reduction with magnesium sulfate after 90 minutes when compared with an ergot alkaloid. An additional study showed improvement in pain reduction with magnesium sulfate after 120 minutes when compared with a systemic corticosteroid plus dopamine antagonist. One study reported 50% pain relief was improved with magnesium sulfate compared with placebo, and another study found that complete pain relief was improved with magnesium sulfate compared with a dopamine antagonist. No difference in the need for rescue analgesia was detected after 30 minutes compared with placebo, and the need for rescue analgesia at any point was improved for the migraine with aura subgroup in 1 study.

The major limitation of the review was the heterogeneous nature of the included studies, which precluded a formal meta-analysis. There was a risk for publication bias and selective reporting, as some randomized control trials were not included. Further, there is a lack of consensus regarding magnesium sulfate dosing for headaches, and researchers noted that possible genetic differences in drug metabolism could account for some of the observed variations in this study’s responses. 

The authors concluded that their review demonstrates the potential benefits of intravenous magnesium sulfate as an analgesic in acute nontraumatic headaches, saying: “While we cannot draw a firm conclusion on the efficacy or benefit of intravenous magnesium sulfate in the treatment of acute non-traumatic headaches, the existing evidence indicated potential benefits in pain control intensity beyond 1 hour, aura duration, and need for rescue analgesia.”

Reference

Miller AC, Pfeffer BK, Lawson MR, Sewell KA, King AR, Zehtabchi S. Intravenous magnesium sulfate to treat acute headaches in the emergency department: a systematic review [published online September 30, 2019]. Headache. doi: 10.1111/head.13648