The airways effects of inhaled chlorbutol in asthmatic subjects

Chlorbutol is an antibacterial and antifungal agent incorporated in terbutaline (Bricanyl) nebulizer solution. Ten stable atopic asthmatic subjects undertook bronchial challenge testing, according to a double-blind protocol. Patients inhaled doubling concentrations of either methacholine (0.13-4.0 mg.ml-1) or chlorbutol (0.16-5.0 mg.ml-1) for 2 min until the forced expiratory volume in one second (FEV1) had fallen by 20% from baseline. If this had not occurred following the administration of the final concentration, then this highest concentration was repeated for 4 min. The nine subjects completing the study had a geometric mean provocation concentration producing a 20% fall from baseline FEV1 (PC20) methacholine of 0.16 mg.ml-1 (range less than 0.125-0.475 mg.ml-1). After inhalation of 2.5 mg.ml-1 chlorbutol one subject experienced a fall in FEV1 greater than 20%. In the remaining eight subjects, inhalation of chlorbutol did not affect airway calibre. We conclude that chlorbutol, in the concentration present in Bricanyl nebulizer solution, has no clinically significant effect on airway calibre.