The objective was to investigate the effect of dry coating of salbutamol sulphate (SS) with magnesium stearate (MgSt) on the kinetics of powder de-agglomeration. The relative de-agglomeration of the MgSt coated SS powders was higher than uncoated SS at all air flow rates; the SS coated with 2 MgSt showed the highest extent of de-agglomeration (> 5 MgSt coated SS > 1 MgSt coated SS). Rate of de-agglomeration was described by a cumulative de-agglomerated versus time profile. Profiles fitted a mono-exponential model and the deagglomeration rate constant (kd) was estimated. No significant differences existed between any of the uncoated and coated powders. The significance of this study relates to the improved aerosolization and de-agglomeration performance of the MgSt coated SS powders with optimum performance of 2 MgSt coated SS. More significant is the finding that no change existed in de-agglomeration rate constants between the coated and uncoated powders, with the potential implications that their aerosol plume concentration and deposition patterns were similar.