INHIBITION OF INHALED METABISULFITE-INDUCED BRONCHOCONSTRICTION BY INHALED FRUSEMIDE AND IPRATROPIUM BROMIDE

1 The effect of inhaled frusemide and high dose inhaled ipratropium bromide on bronchoconstriction induced by inhaled metabisulphite was studied in 10 atopic volunteers. 2 Frusemide (40 mg), ipratropium bromide (0.5 mg) or saline placebo were administered by nebuliser in a double-blind fashion, prior to construction of a dose-response curve to metabisulphite (2.5-100 mg ml-1). 3 Geometric mean of the provocative dose of metabisulphite that caused a 35% fall in specific airways resistance (sGaw) after placebo was 13 (95% confidence intervals CI 4-36-mu-mol) compared with 36 (16-78) mu-mol after ipratropium bromide and 45 (22-94) mu-mol after frusemide. 4 Mean maximum fall in sGaw was 49 (40-57)% after placebo, 11 (0-22)% after frusemide and -1 (-25-22)% after ipratropium bromide. 5 Frusemide significantly protected against metabisulphite induced bronchoconstriction (P < 0.005). The protection from high dose ipratropium bromide was also significant (P < 0.05), but the response was more variable between subjects.