Effects of two doses of cromolyn on allergen-induced late asthmatic response and increased responsiveness

We selected five atopic children with asthma with previously documented late asthmatic response (LAR) associated with increased hyperresponsiveness to methacholine after the inhalation of Dermatophagoides pteronyssinus. The children had four allergen inhalation tests on 4 different days, at least 14 days apart. On days 1 and 4, saline placebo was inhaled 1 hour before the expected onset of LAR, and FEV1 was measured hourly until FEV1 returned within 10% of baseline value; then methacholine challenge was performed. On days 2 and 3, 20 and 40 mg of cromolyn was inhaled double blind 1 hour before the expected onset of LAR. FEV1 and methacholine responsiveness were measured as on days 1 and 4. The two doses of cromolyn significantly delayed the LAR onset without altering the overall LAR magnitude and prevented the allergen-induced increase in methacholine responsiveness. Both these effects were greater at the maximal dose used. We conclude that cromolyn can prevent the allergen-induced increase in methacholine responsiveness and that this effect is not due to alteration in the magnitude of LAR. Our findings reveal a possible explanation of the effectiveness of this drug in the treatment of allergic asthma.