A dry powder inhaler for pulmonary or nasal use, comprising at least inhaler body (100) and a cartridge (110) with one or two compartments (121) each containing one dose of a drug. The compartment (121) has holes (123) to admit air and holes (120) to deliver powder, which, use, communicate with inhalation (102) channel the inhaler body (100). To prevent the powder from leaking through the compartment holes before use, the air admission holes (123) are of reduced dimension, thereby blocking or hindering powder exit under the force of gravity. When the cartridge 110 is inserted inside the inhaler body (100), all its holes (120, 123) are blocked. By sliding the cartridge (110) relation to the body (100) until the inhalation position is reached, the holes (120, 123) come into fluid communication with one another and with the inhalation channel (103), thereby allowing a flow of air to disperse and entrathe dose through the mouthpiece (103). Five embodiments of the invention are disclosed.