Trigger mechanism for an inhaler

A breath-responsive inhaler having a trigger mechanism and an air flow path through which the user inhales. The trigger mechanism including a medicament source, having a primed position in which the inhaler is primed for use and an actuated position in which the medicament source is actuated to dispense a dose of medicament. The trigger mechanism comprises a toggle mechanism 119 for selectively permitting movement of the source from its primed position to its actuated position. The toggle mechanism 119 comprises a vane 110 positioned in the air flow path, the vane 110 being pivoted about a vane pivot, wherein the trigger mechanism is triggered by movement of the vane 110 upon inhalation of the user to move the toggle mechanism 119 between a primed condition in which the medicament source is maintained in its primed position by cooperation with the toggle mechanism 119 and an actuated condition in which the toggle mechanism 119 is disengaged from cooperation with the medicament source.