the drug and a dispensing system which pours the dose of the drug delivered into a collecting chamber a cavity of the nozzle communicates with the collecting chamber through a central channel designed to reduce air flow resistance as much as possible lateral holes provided in the body of the inhaler allow for the passage of air from the outside upon inhalation a negative pressure is created in the chamber in which the dose of powder delivered is collected drawing an air inflow from the outside the air flow is mixed with the medicinal substance particles and through the central channel enters the cavity of the nozzle from where it is directly inhaled application_number US 1178593 A description the inhaler the longitudinal section of which is illustrated in fig1 consists essentially of a nozzle 1 mounted on a main body designated in general by the reference numeral 2 the nozzle 1 has an aperture 3 communicating with an internal cavity 4 tapering towards a circular hole 5 in direct communication with a central channel 6 consisting of a tubular element 7 disposed axially relative to the body 2 and free to rotate relative to the latter with rotations through 180 u00b0 alternately in one direction and in the other this element 7 is integral with a crown 5 39 forming part of the nozzle 1 and defining the hole 5 the crown 5 39 may be similar to that shown in fig2 of applicants 39 british patent 2041763 the body 2 defines a storage chamber 8 for a powdered medicinal substance the volume of this chamber advantageously being such that it contains a sufficient quantity of the drug for a complete treatment.