A trial of nebulized magnesium sulfate to reverse bronchospasm in asthmatic patients

To test the hypothesis that nebulized magnesium sulfate reverses methacholine-induced bronchospasm in asthmatic patients.

Randomized, double-blind, crossover clinical trial.

Center for Asthma and Allergic Diseases, Children's Hospital of Pittsburgh.

Ten patients who were 21 to 37 years old and had stable asthma.

Patients withheld asthma medications for 24 hours before each study day. Patients with baseline forced expiratory volume in one second (FEV1) of less than 80% were excluded. All subjects underwent bronchial methacholine challenge to produce bronchospasm. They then received one of three different nebulized treatments: 2.5 mg albuterol in 3 mL saline, 3 mL magnesium sulfate (268 mmol/L, pH 6.4), or 3 mL normal saline. Patients repeated spirometry 15 minutes after completing the study drug and then received albuterol by metered-dose inhaler. Spirometry was repeated after the metered-dose inhaler. Each patient made three separate visits to receive each of the three medications.

Methacholine reduced each patient's FEV1 by at least 20% at each testing session. Post-methacholine treatment with nebulized albuterol improved FEV1 by a mean of 56% (SD, 19.6%). Nebulized normal saline led to a mean increase in FEV1 of 29% (SD, 26.5%). Nebulized magnesium sulfate improved FEV1 by a mean of 12% (SD, 12.0%) (P = .054 by paired t-test compared with normal saline).

Nebulized magnesium sulfate has a minimal bronchodilatory effect in asthmatic patients with methacholine-induced bronchoconstriction. Responsiveness to magnesium sulfate may be dependent on the mechanism of induction of bronchospasm, and there probably is no role for nebulized magnesium sulfate in the treatment of acute bronchospasm due to cholinergic stimulation.