Evaluation of different anti-asthmatic drugs on cooling-induced bronchoconstriction

Abstract

Inhalation of cold air is a well-recognized cause of bronchoconstriction in asthmatics. Sudden changes in weather temperature outdoors and indoors due to the extensive use of air conditioning in Kuwait is an important existing problem. The aim of this study was to determine the most effective anti-asthmatic drugs for preventing or reversing cooling-induced contraction (CIC). We recorded isometric tension from tracheal strips, and bronchiolar rings were prepared from male Merino sheep in organ baths during stepwise cooling. CIC was tested before and after addition of various standard agents. Disodium cromoglycate (DSG), methyl prednisolone, atropine, aminophylline, isoprenaline and adrenaline were examined in two cases. The first was before cooling and the second was after cooling induced the maximum bronchoconstriction. Cooling to 20°C induced a rapid and reproducible contraction in ovine tracheal and bronchial preparations. On readjustment to 37°C, the tone returned rapidly to basal level. DSG, methyl prednisolone and atropine did not prevent or reverse the CIC. Aminophylline prevented CIC by 70%. It inhibited the peak of cooling response by 70%. β-agonists (isoprenaline and adrenaline) abolished the CIC, and they also rapidly and totally reversed the cooling effect when added at the peak of bronchoconstriction. These results proved that β-agonists are the drugs of choice in preventing the bronchoconstriction before exposure to cold environment and also completely reversing the bronchoconstriction induced after cooling exposure.