Magnesium for Migraine

23 Feb

Migraines are fun to treat. Not so fun for patients but at least we can fix most of them.

It’s always nice to have another tool or two in the armamentarium for treating migraine.

While hardly surprising given this noble element’s history, it turns out magnesium has been studied for migraine before with some equivocal results. This new paper was an interesting read and as I’m prepping for the FCEM critical appraisal exam I may have overthought the stats and methods here. Please let me know if I’m barking up the wrong tree, I’m sure Carley will 😉

The paper:

Comparison of Therapeutic Effects of Magnesium Sulfate vs. Dexamethasone/Metoclopramide on Alleviating Acute Migraine Headache. [pubmed]


  • Study type
    • RCT double blind
  • Population
    • ED patients who someone thought had migraine by ICHD criteria
  • randomisation was computer generated
  • Intervention
    • the drugs appear well blinded
    • 10mg metoclopramide/8mg dex v 1g mag
    • allowed rescue meds but don’t say what they were
  • Power calculation
    • This struck me as a bit funny. They don’t state it clearly but it looks like power was based on a primary outcome of a 2cm difference on pain scale at 2 hrs.
    • It’s also not clear if they’ve done the power calculation to compare one drug versus the other or just looking to see if there was a 2cm pain reduction from baseline at 2 hrs. If it was powered simply to show that either drug is effective at 2 hrs then it’s not really a comparative study.  Here’s the quote to see what you think:
      • With power set at 0.9 (b = 0.01) [Note this must be a simple typo: beta should = 0.1 not 0.01] and error level at 0.05 (a = 0.05), we estimated the minimum sample size for the study to be 31 subjects on each arm to detect a 2-cm difference in the pain intensity score (NRS at baseline vs. NRS at 2 h).


  • 70 patients
  • both interventions worked but mag worked quicker, there’s a nice graph to show the effect
  • as for primary outcome pain score at 2 hrs was 0.66 cm v 2.5 cm with a p value of <0.0001. This also smells a bit funny as if the trial was powered to find a difference of 2 cm between the two drugs and the actual difference they found was only 1.84 cm it’s hard to see how that gets them a p value with so many zeroes. However if the trial was powered to show that either drug can reduce headache from baseline then the p value makes sense.


  • the big issue here is what they were actually testing. from reading the conclusions the authors make it looks like a comparative trial but if it is then the stats look and power calculation don’t smell right.
  • setting aside the complicated machinations of the stats that I may be misinterpreting, it seems from simply looking at the numbers that this seems to have an effect. Whether or not it’s better is up for debate and it may well be the natural course for migraines to get better over time no matter what we do.
  • as always would be nice to see a bigger study in a setting more similar to ours.


Some other magnesium headache studies (from the reference list)

  • Cete Y, Dora B, Ertan C, Ozdemir C, Oktay C. A randomized pro- spective placebo-controlled study of intravenous magnesium sulphate vs. metoclopramide in the management of acute migraine attacks in the emergency department. Cephalalgia 2005;25: 199–204.
  • Corbo J, Esses D, Bijur PE, Iannaccone R, Gallagher EJ. Randomized clinical trial of intravenous magnesium sulfate as an adjunctive medication for emergency department treatment of migraine head- ache. Ann Emerg Med 2001;38:621–7.

Some #FOAMed

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