The purpose of this study was to compare the effectiveness of an eight day treatment with clinically relevant doses of a fixed combination of the β2 mimetic reproterol hydrochloride and disodium cromoglycate with each agent given alone against antigen-induced early (EAR) and late airway responses (LAR) as well as post-antigen-induced airway hyperresponsiveness (AHR) in allergic sheep. Animals were treated in a randomized fashion with either the inhaled combination (n = 6), reproterol hydrochloride alone (n = 6), disodium cromoglycate alone (n = 6), or placebo (n = 8). Treatments (two puffs from a metered dose inhaler) were given three times a day for 7 days and once on the 8th day 1 h before airway challenge with Ascaris suum antigen. In the placebo trial, antigen challenge resulted in EAR and LAR as measured by increases in specific lung resistance. these changes were followed 24 h later by AHR to inhaled carbachol hydrochloride reduced the EAR (P < 0.05) and blocked the LAR (P < 0.05), but had no effect on the post-challenge AHR. Treatment with disodium cromoglycate also reduced the EAR (P < 0.05), blocked the LAR (P < 0.05), and blocked the post-antigen-induced AHR (P < 0.05). Treatment with the fixed combination reduced the EAR (P < 0.05), blocked the LAR (P < 0.05), and blocked the post-antigen-induced AHR (P < 0.05). Comparison of the different agents indicated that the fixed combination gave significantly increased protection against the EAR than either agent alone, gave slightly better (P < 0.05) protection against the late response than cromolyn sodium and gave better protection against post-antigen-induced AHR than reproterol hydrochloride alone. These results suggest that a fixed combination of a β2-mimetic and disodium cromoglycate provides some increased protection against antigen-induced airway responses when compared to either agent alone in a controlled laboratory setting.
- Airway hyperresponsiveness
- Allergen challenge
- Late phase response
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine