Assuming an intra-subject coefficient of variation (CV) of 33% (based on the variability of AUC0-12 for budesonide and AUC0-12 and Cmax for formoterol observed in a similarly designed crossover study in healthy adults), 44 evaluable subjects will give at least 80% power to show that the 90% CI for the treatment effects lies entirely within the range 0.8 to 1.25, i.e., would rule out a 20% change (on a log scale) in exposure to budesonide and formoterol.