A dry powder inhaler suitable for pulmonary or nasal delivery, comprising an inhaler body (201; 801) and a cartridge (203; 803); the inhaler comprising: (a) the inhaler body (201; 801) comprising a mouthpiece, a bottom channel inlet (210; 310; 410; 510; 610; 810), an inhalation channel (208, 808) for providing fluid communication between the patient's mouth when engaged with the mouthpiece and the bottom channel inlet (210; 310; 410; 510; 610; 810), at least one side inlet for allowing direct air admission from atmosphere into the inhalation channel (208, 808); an inhaler body opening (204; 804) formed therein and defined between opposing top (211; 811) and bottom walls and opposing side walls, said inhaler body opening (204; 804) having at least one open end by means of which the cartridge (203; 803) is insertable into the opening (204, 804) and having at least one air inlet opening (815, 816) for admitting air into the inhaler body opening (204; 804), means for guiding movement of the cartridge (203; 803) in the inhaler body opening (204, 804) relative to the body (201; 801) and control its travel from a storage position into an inhalation position; (b) the cartridge (203; 803) being shaped for engagement in the inhaler body opening (204; 804) and having at least one substantially cylindrical powder compartment (205; 305; 405; 505; 605; 705; 805) formed therein for carrying a powder-based medicament, and at least one air inlet vent (206, 209; 306, 309; 406, 409; 506, 509; 606, 609; 709; 806, 809); the powder compartment having an outlet (207; 807) which allows fluid communication with the body inhalation channel (208; 808) through the body bottom channel inlet (210; 310; 410; 510; 610; 810) and at least one pin for engaging with the body guiding movement means; wherein the cartridge (203; 803) is slidable within the body (201; 801) between a storage position in which the at least one air inlet vent (206, 209; 306, 309; 406, 409; 506, 509; 606, 609; 709; 806, 809) of the cartridge is substantially sealed by the inhaler body such that there is no fluid communication to the cartridge, to an inhalation position, in which the or each air inlet vent (206, 209; 306, 309; 406, 409; 506, 509; 606, 609; 709; 806, 809) of the cartridge is substantially aligned with an associated air inlet opening (815, 816) of the inhaler body such that there is fluid communication between the inlet opening (815, 816) of the inhaler body, the or each air inlet vent (206, 209; 306, 309; 406, 409; 506, 509; 606, 609; 709; 806, 809) of the cartridge, the cartridge top outlet (207; 807) and the mouthpiece channel (208; 808); characterized in that the cartridge (203; 803) includes at least two air inlet vents (206, 209; 306, 309; 406, 409; 506, 509; 606, 609; 709; 806, 809), at least one of which is a lateral air inlet vent (209; 309; 409; 509; 609; 709; 809) and the inhaler body (201; 801) has an air inlet opening (815, 816) associated with each of the air inlet vents (206, 209; 306, 309; 406, 409; 506, 509; 606, 609; 709; 806, 809) of the cartridge which allow admission of air from the atmosphere into the cartridge powder compartment (205; 305; 405; 505; 605; 705; 805) when the cartridge (203; 803) is in the inhalation position; and the inhaler body bottom channel inlet (210; 310; 410; 510; 610; 810) further comprising at least one orifice which forms a sharp constriction in the fluid flow path from the cartridge powder compartment outlet (207; 807) into the inhalation channel (208; 808) when the powder cartridge (203; 803) is moved into the inhalation position. (a) the inhaler body (201; 801) comprising a mouthpiece, a bottom channel inlet (210; 310; 410; 510; 610; 810), an inhalation channel (208, 808) for providing fluid communication between the patient's mouth when engaged with the mouthpiece and the bottom channel inlet (210; 310; 410; 510; 610; 810), at least one side inlet for allowing direct air admission from atmosphere into the inhalation channel (208, 808); an inhaler body opening (204; 804) formed therein and defined between opposing top (211; 811) and bottom walls and opposing side walls, said inhaler body opening (204; 804) having at least one open end by means of which the cartridge (203; 803) is insertable into the opening (204, 804) and having at least one air inlet opening (815, 816) for admitting air into the inhaler body opening (204; 804), means for guiding movement of the cartridge (203; 803) in the inhaler body opening (204, 804) relative to the body (201; 801) and control its travel from a storage position into an inhalation position; (b) the cartridge (203; 803) being shaped for engagement in the inhaler body opening (204; 804) and having at least one substantially cylindrical powder compartment (205; 305; 405; 505; 605; 705; 805) formed therein for carrying a powder-based medicament, and at least one air inlet vent (206, 209; 306, 309; 406, 409; 506, 509; 606, 609; 709; 806, 809); the powder compartment having an outlet (207; 807) which allows fluid communication with the body inhalation channel (208; 808) through the body bottom channel inlet (210; 310; 410; 510; 610; 810) and at least one pin for engaging with the body guiding movement means; wherein