Protective effect of drugs on bronchoconstriction induced by sulphur dioxide.

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Abstract
The response to inhaled SO2 in 8 normal, 7 atopic and 22 asthmatic subjects was studied by measuring thoracic gas volume and airway resistance in a whole body plethysmograph. The fall in specific airway conductance in relation to the concentration of SO2 inhaled (0-20 ppm) was determined in all 3 groups. The specific airway conductance fell significantly in the atopic and asthmatic subjects but not in the normal group. In a double-blind study, prior inhalation of disodium cromoglycate caused a significant reduction in the response to SO2 inhalation in atopic and asthmatic subjects. Prior treatment with inhaled ipratropium bromide blocked the response in the atopic subjects, but the effect was variable in the patients with asthma. Previous treatment with inhaled clemastine also reduced the response in patients with asthma, without causing a change in baseline specific conductance. Non-allergic bronchial hyperreactivity was increased in the atopic and the asthmatic subjects, and mediator release, in addition to a vagal reflex, has a role in such bronchoconstriction.