CF patients are instructed to inhale dornase alpha 30 minutes before airway clearance techniques. This has always been based on lore and plausibility.
Dentice & Elkins publish their meta-analysis of 5 studies, including a total of 122 patients who were randomized and crossed-over to test the effect of the timing of dornase inhalation on outcomes. There was no difference in FEV1, FVC, quality of life or numerous secondary outcomes according to whether dornase was inhaled before or after airway clearance. Cochrane Database Sys Rev 2011;5:CD007923.