title: Effect of inhaled magnesium sulfate on sodium metabisulfite-induced bronchoconstriction in asthma.
abstract: BACKGROUND
  Inhaled magnesium (Mg) seemed to have a mild protective (nonbronchodilator) effect against histamine and methacholine. Inhaled sodium metabisulfite (MBS) causes bronchoconstriction in asthma through indirect mechanisms that involve sensory nerve stimulation, and it is extensively used to study airway hyperresponsiveness. We designed this double-blind, randomized, crossover, and placebo-controlled study to test the effect of nebulized Mg sulfate against indirect challenge with MBS.
  
  
  METHODS
  Ten asthmatic subjects (three male) aged 38.8 (3.29, SEM) years came on three occasions to perform MBS challenges 5 min after inhalation of either normal saline solution as placebo or Mg sulfate (4 mL; 286 mOsm). Doubling increasing concentrations of MBS were administered by continuous nebulization at tidal breathing during 1 min starting at 0.3 to 80 mg/mL until a >20% fall in FEV1 (PC20) from post saline solution baseline value was achieved. PC20 values were logarithmically transformed before analysis.
  
  
  RESULTS
  The mean baseline FEV1 at control day was 2.52 (0.14) L and 88.46 (4.28) percentage predicted, while the geometric mean MBS PC20 was 1.95 (1.38, geometric SEM) mg/mL. After placebo, the geometric mean PC20 was 2.26 (1.26) mg/mL. Inhaled Mg increased significantly the PC20 to 5.06 (1.52) mg/mL; p<0.05. Mg diminished the bronchoconstrictor response to MBS by 1.3 doubling doses (p=0.08).
  
  
  CONCLUSIONS
  Inhaled Mg attenuates MBS-induced bronchoconstriction in these asthmatic subjects. This new feature of Mg, even modest in magnitude, emphasizes the necessity of studying the potential role of this cation in modulating airway response.
authors.affiliation: Pulmonary section, Granadero Baigorria Hospital, Universidad Nacional de Rosario School of Medicine, Argentina.
authors.forename: L J
authors.initials: LJ
authors.lastname: Nannini
authors.forename: D
authors.initials: D
authors.lastname: Hofer
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D016084:Bronchoconstriction / Q000187:drug effects*; D016085:Bronchoconstrictor Agents / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008278:Magnesium Sulfate / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D009330:Nebulizers and Vaporizers; D013447:Sulfites / Q000494:pharmacology*
chemical_list: D016085:Bronchoconstrictor Agents; D013447:Sulfites; C005200:sodium metabisulfite; D008278:Magnesium Sulfate