Abstract: An inhalation device is provided for use with an aerosol container having a body portion and a discharge stem movable with respect to the body portion from a rest position in which discharge is prevented to an operative position in which discharge takes place. The device has a housing for the inhalation device, and an outlet provided in the housing through which a patient can inhale. A restraining and pressure-sensing member is provided in the form of a resiliently flexible plate. The plate has a first position in which it prevents relative movement between the discharge stem and the body portion to the operative position and a second position in which it permits such movement. The plate senses when a reduced pressure is produced through inhalation by the patient and moves from the first position to the second position in response thereto.