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Magnesium Does Not Appear to Reduce Death, Disability from Stroke, May Be Beneficial in Lacunar Infarct: Presented at ISC

By Charlene Laino

SAN DIEGO, CA -- February 9, 2004 -- Magnesium sulfate administered within 12 hours of acute stroke does not significantly reduce chances of death or disability, although it may be of benefit in lacunar stroke, say investigators.

Kennedy R. Lees, MD, Professor of Cerebrovascular Medicine at the University of Glasgow, Gardiner Institute, in Glasgow, United Kingdom, presented results here on behalf of the Intravenous Magnesium Efficacy in Stroke Trial (IMAGES) study investigators, on February 6^th at the American Stroke Association's 29^th International Stroke Conference.

Dr. Lees said that animal models, which showed that magnesium to be neuroprotective, and pilot studies that suggested a potential benefit in small numbers of people provided the rationale for the trial.

The randomized, double-blind, placebo-controlled, multicenter collaborative trial - the largest acute neuroprotective trial undertaken to date, according to the investigators - was designed to test whether magnesium sulfate, given by intravenous infusion for 24 hours within 12 hours of onset of clinically diagnosed acute stroke, reduces death and disability at 90 days.

For the study, 2,589 patients were randomized within 12 hours of acute stroke to receive 16 mmol of magnesium sulfate, intravenously over 15 minutes, followed by 16 mmol of magnesium sulfate over 24 hours, or matching placebo. Treatment began within 6 hours of stroke onset in 37% of the patients; median time to treatment was 7 hours.

The average age of the patients, 53% of whom were male, was 70 years. Thirty-two percent of patients had a lacunar infarct.

The primary outcome, a global endpoint statistic expressed as the common odds ratio for death or disability at 90 days, was not improved by magnesium treatment, the study showed. Dr. Lees was the odds ratio was 0.95, which was not significant at the P = .59 level.

No difference was demonstrated between the magnesium-treated patients and placebo patients in any of the secondary endpoints of mortality and death or disability, as measured by a Barthel score of less than 95 and a modified Rankin scale of greater than 1. Patients in the magnesium arm were 18% more likely to die by day 90 than those in the placebo arm, Dr. Lees said, but this was not significant at the P = .098 level.

When looked at by subgroup, treatment did not affect outcome for those patients treated within 6-hours versus those treated outside the 6 hour window, nor for patients who suffered ischemic versus non-ischemic strokes.

However, patients who experienced lacunar strokes were 30% less likely to die or result in a disability compared with placebo-treated patients. This was significant at the P = .0045 level.

Since lacunar strokes are traditionally associated with a history of hypertension and the study also showed a benefit of magnesium treatment in patients with baseline mean arterial blood pressure above the median, some biological interaction may be at play that needs further analysis, he said.

Dr. Lees said the further follow-up studies of patients with lacunar strokes are clearly justified. "Magnesium costs only $1 or $2 a day and it could help 1 in 10 patients returned to normal."

Dr. Lees also suggested several hypotheses for why magnesium did not produce any overall benefit. First, the median time to treatment was 7 hours, with only 3% of patients treated within 3 hours. The longer the time from symptom onset, the smaller the volume of brain tissue available for salvage, he suggested.

Also, the sample size may have been too small to demonstrate a small but clinically relevant benefit, he said.


[Study title: Intravenous Magnesium Efficacy in Stroke Trial (IMAGES): Final Results. Abstract 34]

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