An inhalation-activated inhalator having a primary inhalation passage and a secondary inhalation passage disposed in communication with the primary inhalation passage and a source of medicament. The primary inhalation passage has airflow inhibiting mechanism connected to a blocking plate positioned to selectively block fluid flow in the secondary inhalation passage. As the user's inhalation reaches a defined rate, the flow inhibiting mechanism restricts flow through the primary inhalation passage and moves the blocking plate to enable airflow through the secondary passage. Thus, as the user achieves a desired inhalation rate, the medicament is provided through the secondary inhalation passage, thereby optimizing the delivery of medicament to the lungs.