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

A method of operating a dry powder inhaler having a first generally planar spiral travel path, wherein the first spiral travel path has a plurality of adjacent curvilinear channels forming lanes with respective laterally spaced apart upstanding sidewalls, including an inner lane and an outer lane, the method comprising:

• slidably advancing a plurality of discrete sealed microcartridges with substantially rigid bodies along the first travel path toward an inhalation chamber that merges into an inhalation output port, wherein the microcartridges are oriented in the channels so that outer walls thereof reside proximate respective laterally spaced apart channel sidewalls and bottoms thereof face a floor of the channel, and wherein outer walls of neighboring microcartridges are in abutting contact during the slidably advancing step.