IMPORTANT! Updated July 1, 2020
In Summary, for those who took the magnesium:

Benefits in NNT

  • 67% saw no benefit
  • 33.3% of severe asthmatics were helped by preventing hospital admission
  • 1 in 3 were helped (preventing hospital admission if patient is a "severe asthmatic")
  • None were helped (preventing hospital admission if patient is not a "severe asthmatic")

Harms in NNT

  • 0% of severe asthmatics were harmed by serious side effects
  • 100% of non-severe asthmatics were neither helped nor harmed
  • None were harmed (serious side effects, vital sign abnormalities)

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Source: Rowe BH et al. Magnesium sulfate for treating exacerbations of acute asthmain the emergency department. Cochrane Database Syst Rev. 2000;(2):CD001490.

Efficacy Endpoints: Hospital admission

Harm Endpoints: Tachycardia, tremor

Narrative: This review included 7 trials, (N = 665) of which 5 were adult and 2 pediatric. Magnesium sulfate was administered early in the study period, in the first 60 minutes in 5 of the studies. Administration was intravenous, given via bolus in 6 out of 7 studies, 1.2-2 grams over 20 minutes (in pediatrics, 25mg/kg or 100mg/kg). Overall, there was considerable heterogeneity in the pooled results when all trials were included. Accordingly, a pre-planned subgroup analysis was performed on patients labeled severe, defined variably by clinical findings or airflow measurements, within the individual studies. This analysis included 133 patients and had no heterogeneity. It was in this group that a profound effect of magnesium sulfate on the admission rate (NNT 2) was found.

Caveats: Magnesium sulfate would seem to have limited benefit in non-severe asthma exacerbations and dramatic effects in the severe subgroup; however, this analysis was rather small so caution should be used in the application of these numbers.

Author: Ashley Shreves, MD

Published/Updated: January 10, 2010

  1. The Title Bar

    The title bar is color-coded with our overall recommendation.

    • Green: Benefits outweigh risks.
    • Yellow: Unclear risk/benefit profile.
    • Red: Benefits do not outweigh risks.
    • Black: Obvious harms, no clear benefits.
  2. Tip content...