Bronchial provocation testing is most commonly used for assessing the severity of bronchial responsiveness and its modulation by drugs.’ Traditionally, the pharmacologic agents histamine and methacholine have been used for bronchial provocation testing. These agents act directly on specific receptors causing bronchial smooth muscle to contract. Bronchial provocation using indirect stimuli such as exercise, cold air, hyperosmolar saline, distilled water, and sulphur dioxide have been less used in the routine lung function laboratory. Provocation testing with indirect stimuli has an advantage over pharmacologic stimuli in that indirect stimuli cause the endogenous release of mediators to which the subject is sensitive. Thus challenge with an indirect stimulus may be preferred to provoke airway narrowing when investigating the effects of drugs that act to reduce the availability of mediators of bronchoconstriction.
We have developed and standardized a bronchial provocation test using a hyperosmolar (4.5 percent) saline aerosol. Hyperosmolar saline aerosol causes the release of histamine and other mediators from human lung mast cells. In asthmatics, the airway response to hyperosmolarity is inhibited by antihistamines. Hyperosmolarity may also stimulate sensory nerves to release neuropeptides causing the airways to narrow. canadian neightbor pharmacy
Aerosol corticosteroids and sodium cromoglycate are widely used in the treatment of asthma. Chronic treatment with inhaled corticosteroids results in, among other things, a reduction in mast cell number and thus the availability of histamine and other mast cell mediators. The mechanism for sodium cromoglycate is not precisely known, but it does reduce human mast cell release of histamine in response to hyperosmolarity. It is also thought to have an action on sensory nerves. We have previously reported the acute inhibitory effect of sodium cromoglycate and nedocromil sodium on challenge with hyperosmolar saline aerosol compared with a placebo. We have also reported that chronic treatment with aerosol beclomethasone dipropionate reduces sensitivity to 4.5 percent saline aerosol. We noted that treatment with beclomethasone, while reducing airway sensitivity to hyperosmolar saline, did not prevent the airways from excessively narrowing when the duration of exposure to the same concentration of hyperosmolar saline aerosol was increased.
The aim of this study was to investigate the acute effect of sodium cromoglycate on airway responses to a hyperosmolar aerosol both before and during treatment with inhaled corticosteroids. The group of patients who had asthma came to the laboratory for assessment of their asthma severity and their response to treatment.