Inhalation device

A breath-actuated aerosol dispenser comprising a housing defining a patient port and containing an aerosol container equipped with a metered dose dispensing valve, a primer movable between a rest position and a priming position in which it applies a force sufficient to actuate the dispensing valve, and a breath-actuated trigger mechanism which prevents actuation of the dispensing valve until a triggering air flow passes through the patient port, wherein the primer comprises a spring and a cage, the spring being positioned within the cage such that the spring is maintained in a partially compressed state when the primer is in its rest position and such that no substantial force is applied by the spring to the aerosol container, dispensing valve, or breath-actuated trigger mechanism in the rest position, the cage comprising a top element which engages a top end of the spring and a bottom element which engages a bottom end of the spring so as to hold the spring in said partially compressed state when the primer is in its rest position, said top element and said bottom element of the cage being movable within the housing.