The results of this study confirm that the acute administration of sodium cromoglycate is very effective in preventing airway narrowing induced by a hyperosmolar stimulus. The results show, for the first time, that sodium cromoglycate provides additional protection when given during treatment with aerosol steroids. Further, the reduction in bronchial responsiveness to hyperosmolarity occurred in some patients independently of any improvement in resting lung function and when lung function was within normal limits.
These findings have important clinical implications for patients being treated for asthma with aerosol corticosteroids. We have previously reported that 8 weeks treatment with beclomethasone dipropionate (600 to 1,500 |Hg/d) reduces airway sensitivity to 4.5 percent saline aerosol in patients with asthma. In that study, 12 of 13 patients studied however; remained responsive to saline aerosol, and the treatment with beclomethasone did not prevent the airways from excessively narrowing in 10 of 13 patients. Thus, with increased time of exposure to the same concentration of saline aerosol, the airways still narrowed after treatment with beclomethasone. www.canadian-familypharmacy.com
The findings in this study suggest that the majority of patients receiving 1,000 |ig of budesonide for 24 to 56 days also remain reactive to this stimulus, although their sensitivity was reduced. We have reported exercise-induced asthma in patients taking beclomethasone regularly over 2 to 3 months. Indeed, daily treatment with this steroid is not an exclusion criteria for studies of exercise-induced asthma. Our findings with 4.5 percent saline aerosol are consistent with these observations as exercise is thought to provoke airway narrowing by airway drying and an increase in osmolarity of the surface fluid.
We have shown that bronchial responsiveness can still remain during treatment with steroids and when lung function is within the normal predicted range. In such patients, the addition of sodium cromoglycate would seem to be warranted, particularly when given immediately before stimuli known to provoke airway narrowing indirectly; eg, cold air, exercise, allergens, sulphur dioxide, and fog. In fact, for all but two patients there was total inhibition of the response to 4.5 percent saline aerosol after sodium cromoglycate in the presence of steroids.
This study also shows the usefulness of bronchial provocation testing using an indirect stimulus for provoking airway narrowing and to assess drug effects. Sensitivity to hyperosmolarity reflects the presence of inflammatory mediators, and a decrease in this sensitivity with long-term treatment with corticosteroids is probably a result of a reduction in airway inflammation.