Effect of inhaled heparin on water-induced bronchoconstriction in allergic asthmatics.

ABSTRACT

OBJECTIVE: The aim of this study was to investigate the effect of inhaled heparin on bronchoconstriction induced by ultrasonically nebulised distilled water (UNDW) in allergic asthmatics. METHODS: Eight atopic asthmatics, hyperresponsive to UNDW, were selected for this randomised, placebo-controlled, crossover double-blind study. On two consecutive days, these subjects underwent a UNDW challenge 45 min after inhaling aerosolised heparin (1000 U/kg) or placebo. RESULTS: Neither heparin nor placebo had a significant effect on base-line forced expiratory volume in 1 s (FEV1), but heparin significantly attenuated UNDW-induced bronchoconstriction, as shown by its efficacy in preventing the decreases in FEV1 produced by all doses of water (in comparison with placebo P < 0.05 after 2 ml water; P < 0.01 after 4, 8 and 16 ml water). CONCLUSION: Inhaled heparin is able to exert a protective effect against the bronchoconstrictive response to UNDW in allergic asthmatics, and this action is likely due to inhibition of mast cell degranulation.