The utility of methacholine airway responsiveness measurements in evaluating anti-asthma drugs
Abstract
Measurements of airway responsiveness are frequently used to evaluate anti-asthma drugs. This study investigated the utility of methacholine airway responsiveness measurements in evaluating anti-asthma medications, both in terms of a bronchoprotective effect and the ability to attenuate allergen-induced methacholine airway hyperresponsiveness. Methacholine airway responsiveness was measured as PC20 on two occasions (separated by 35+/-17 days, mean +/- SD) in 40 subjects with mild, stable asthma. Additional subjects had PC20 measurements made before and after administration of either inhaled salbutamol (200 microg) (n = 20) or allergen inhalation challenge (n = 31). The reproducibility of the methacholine PC20 with this method was high (intraclass correlation coefficient = 0.94). The average shift in PC20 after salbutamol was 4.11 doubling concentrations (SD = 1.08). On the basis of these results, a sample size of 12 subjects would be required to demonstrate a 1 doubling concentration difference in the bronchoprotective effect of two drugs with a 90% power. The average shift in PC20 after allergen was 1.29 doubling concentrations. On the basis of these results and an estimated SD of 0.96, a sample size of 24 subjects would be re...Continue Reading
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