Atopic asthma is a chronic inflammatory disorder of the airways associated with airway hyperresponsiveness to various bronchoconstrictor stimuli. There are several pharmacologic agents, involved in the inflammatory process, that can produce acute bronchoconstriction, such as metacholine. Heparin possesses multiple noncoagulant properties, including anti-inflammatory actions.
Objectives: The purpose of the present study was to investigate the effect of inhaled heparin on the airway response to metacholine in children with asthma.
Methods: Fifteen children with mild atopic asthma participated in the study. It was randomized, double-blind, cross-over, placebo controlled study. There were three study visits. At the first visit patients were included into the study and beta-agonists were withheld for at least 12 hours before the next visit (second day). At the second visit provocation test with metacholine, inhalation with single dose of heparin or placebo followed by provocation test with metacholine were performed. After two weeks, tests were performed in the same manner except of that patients instead of heparin inhaled placebo or opposite.
Results: Fourteen children completed the study. Single dose of inhaled heparin significantly decreased bronchial hyperresponsiveness to metacholine when compared to placebo.
Conclusion: The exact mechanism of anti-inflammatory role of heparin is still under investigation and needs to be studied further. The possible anti-inflammatory effect of heparin can be through effect on the neuronal M2 receptors or on receptor-protein G binding or direct effect on the smooth muscles, and in such mechanisms, heparin can decrease bronchial hyperreactivity to metacholine.