Inhalation device

A dry powder inhaler for dispensing powdered medicament, comprising a housing defining a chamber for receiving a dose of powdered medicament, one or more air inlets, and a patient port adapted for insertion into the mouth or nasal passage of the patient, said housing being constructed and arranged to provide an air passage extending from the air inlet(s) through the chamber to the patient port so that patient inhalation at the patient port generates an airstream through the inhaler which entrains particles of medicament from the chamber for inhalation by the patient, the air passage being provided with one or more deagglomeration channels between the chamber and patient port through which the airstream with entrained medicament must pass, each channel having a substantially constant cross-sectional profile with a cross-sectional area no greater than 40 mm.sup.2, a first opening communicating with the chamber, a second opening communicating with the patient port, and adjacent said first opening a first bend of 35.degree. to 200.degree. and adjacent said second opening a second bend of 35.degree. to 200.degree., wherein the minimum radius of curvature of the center of each of the first and second bends is no greater than 10 mm, said first and second bends being of opposite-handedness so as to form an S shape.