The present invention provides a medical aerosol suspension formulation of MDI administration, comprising: a) micronized pa-agonist； b) micronized corticosteroid； c) a sib-therapextric quantity of a moisture-scavenger excipient； and d) a HFA propellant； wherein (a), (b), and (c) and their respective relative amounts are selected such that they associate to form floccules having a density substantially the same as that of the HFA propellant.
