Magnesium in Stroke: Does It Reduce Disability?

Mark J. Alberts, MD


February 28, 2014

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Hello, and welcome to this Medscape stroke update. I am Dr. Mark Alberts, Vice Chair of Neurology at UT Southwestern in Dallas, Texas. Today I want to update you about a new study,[1] the results of which were just reported at the International Stroke Conference held in February 2014 in San Diego, California. The long-awaited results of the FAST-MAG trial were reported by Dr. Jeff Saver, head of the stroke center at UCLA. This trial was unique for a number of reasons. Dr. Saver and his colleagues were able to treat over 1700 patients, the vast majority of whom received treatment within 1 hour of stroke onset.

How did he and his colleagues do this? The patients typically were treated in the ambulance that went to get the patient after 911 was called. Patients were diagnosed by the paramedics, and the randomization kits and magnesium were stored in the ambulance so that patients could be treated, often within 15 minutes of the arrival of the ambulance. This was remarkable. I am aware of no other stroke study in which patients were treated so rapidly after stroke onset. In fact, about three quarters of the patients were treated within 1 hour of stroke onset. The treatment was 4 grams of magnesium in the ambulance and then 16 grams of magnesium during the next 24 hours, after the patient was admitted to the hospital.

What were the results in terms of neurologic function after 3 months? Overall, these were disappointing. This double-blind trial found no evidence of efficacy for any neurologic or clinically meaningful endpoint in the magnesium group vs the placebo group. Why was that the case? Certainly it was not because the patients were not treated rapidly enough; these patients were treated as rapidly as is feasible for any acute stroke study. Perhaps magnesium is not a potent enough neuroprotective agent, despite studies in the past and animal studies showing that it should have some efficacy. But I believe one important factor is that, in FAST-MAG, about 40% of patients were also treated with IV tPA (tissue plasminogen activator).

Patients got into the EMS system and were transported to the hospital rapidly. It may be that the effects of IV tPA were so significant -- and we know that IV tPA is fairly efficacious -- that they neutralized any secondary effects that magnesium, as a neuroprotective agent, could have been shown to have in the study. That is just a hypothesis. We will have to delve into the study in more detail. Looking at the tPA- and non-tPA-treated patients, there did not seem to be much of a difference in terms of overall effects of magnesium, at least in the data Dr. Saver presented at the meeting; but again with so many patients receiving tPA, this may have diluted the effects of the neuroprotective agent.

Dr. Saver and his colleagues should be complimented on this extremely well-done study. They set the bar very high in terms of treating patients with acute stroke in as rapid a manner as is feasible.

Thank you very much for joining me for this Medscape stroke update. Have a good day.


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