Seasonal increase of carbachol airway responsiveness in patients allergic to grass pollen. Reversal by corticosteroids.

By measuring airway resistance (Raw) as an index of response, dose-response curves to aerosolized carbachol were constructed in 10 patients suffering from grass pollen allergy. The subjects were first tested before the pollen season (March). During the pollen season (May and June), another control test was performed; the patients were then treated (double blind and at random) with placebo or methylprednisolone (16 mg/day given orally) for 7 days and then retested. After a 10-day interval devoid of treatment, the 2 treatments were crossed over and a fourth carbachol test was performed. Baseline function values were comparable for all 4 tests. In all but one subject (who was a smoker), carbachol increased Raw by more than 150% over baseline for each of the 4 tests. In these 9 patients, carbachol responsiveness significantly increased during the pollen season and returned to its preseason level after corticosteroid treatment. The data suggest that airway inflammation was responsible for the seasonal increase in airway reactivity.