FAST-MAG Published: A New Window for Stroke Therapy?

February 04, 2015

The FAST-MAG (Field Administration of Stroke Therapy–Magnesium) trial of prehospital magnesium therapy in stroke patients has been published in the February 5 issue of the New England Journal of Medicine.

The study, which was first presented last year at the American Stroke Association International Stroke Conference and reported by Medscape Medical News at that time, failed to show an effect of intravenous magnesium sulfate started in the ambulance on 90-day disability outcomes in patients with suspected stroke, but it did demonstrate that such prehospital treatment was safe and feasible.

The authors, led by Jeffrey L. Saver, MD, from the University of California Los Angeles, point out that although the primary finding of the efficacy of magnesium sulfate as a neuroprotectant was negative, the study has several positive messages.

In particular, the trial delivered the study agent to patients with a suspected stroke faster than any previous pivotal trial, with 74% of the patients treated in the first 60 minutes after the onset of stroke. Researchers also had a high success rate (96%) in identifying stroke patients in a prehospital setting.

"A New Time Window" for Stroke Treatment

"The FAST-MAG trial has opened up a new time window for stroke therapeutics," Dr Saver commented to Medscape Medical News. "The 'golden hour' — the first 60 minutes after onset when almost all brain tissue is still salvageable — is now a potential treatment window. The challenge now is to find agents that will be effective in this earliest epoch."

He added: "The FAST-MAG trial pioneered methods for paramedics to test promising agents in stroke in the first minutes after onset. Other studies worldwide are now using these methods to test drugs in the 'golden hour' in acute stroke patients, including studies of nitroglycerin for stroke in California and Great Britain and a study of the nitric oxide blocker NA-1 for stroke in Canada."

In the paper, the researchers note: "In addition to testing magnesium sulfate specifically, we performed the FAST-MAG trial with the broad central aim of developing and validating methods that can be used in pivotal trials of neuroprotective treatments in the prehospital setting."

To identify patients with a suspected stroke for enrollment in the study, they used a two-stage screening process. This involved paramedics performing the Los Angeles Prehospital Stroke Screen, an eight-item inventory taking 1 or 2 minutes, followed by physician review by phone with the paramedic and the patient or an on-scene legally authorized representative.

The study randomly assigned 1700 patients with suspected stroke to receive intravenous magnesium sulfate or placebo, beginning within 2 hours after symptom onset. Paramedics gave a loading dose before hospital arrival, and a 24-hour maintenance infusion was started at hospital arrival.

Final diagnosis showed that 73.3% of patients had an ischemic stroke, 22.8% had an intracranial hemorrhage, and 3.9% had a stroke-mimicking condition. Median time to treatment from symptom onsite was 45 minutes.

Results showed no significant shift in the distribution of 90-day disability outcomes on the global modified Rankin Scale (the primary outcome) between patients in the magnesium group and those in the placebo group, with mean scores of 2.7 in each group.

There was also no significant difference between the two groups in mortality (15.4% magnesium versus 15.5% placebo) or serious adverse events.

The FAST-MAG study was supported by the National Institute of Neurological Disorders and Stroke.

N Engl J Med. 2015;372:528-536. Abstract

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