Methods of operating dry powder inhalers having spiral travel paths with microcartridges of dry powder

Dry powder inhalers include: (a) a first generally planar spiral travel path in an inhaler body, wherein the first spiral travel path has a plurality of adjacent curvilinear channels forming lanes with upstanding sidewalls, including an inner lane and an outer lane; and (b) a plurality of discrete sealed microcartridges with substantially rigid bodies disposed in the first travel path, each comprising a pre-metered (typically dose) amount of dry powder, the microcartridges being configured to slidably advance along the first travel path toward an inhalation chamber that merges into an inhalation output port. In operation, at least one microcartridge is held in the inhalation chamber to release the dry powder therein during inhalation.