A single-dose dry powder inhaler, comprising a base assembly comprising a chamber configured to receive a medication; and a mouthpiece assembly comprising air intake passages for supplying air into the inhaler, a rotation chamber for generating an aerosol of the medication, wherein the rotation chamber is in air communication with the air intake passages, a tube comprising an internal passage in air communication with the rotation chamber for discharging the aerosol of the medication and administering said aerosol to a patient; wherein the base assembly and the mouthpiece assembly are configured such that the inhaler is capable of assuming an open configuration, in which access to the chamber of the base assembly is provided for inserting therein the medication, and a closed configuration, in which the chamber of the base assembly is in air communication with the rotation chamber of the mouthpiece assembly for transferring the medication from the chamber to the rotation chamber for forming out of it the aerosol of the medication, characterized in that at least one of the air intake passages and the tube of the mouthpiece assembly is selectable, and in that the air intake passages have a ratio of one of the transverse dimensions (H, W) to the other of the transverse dimensions (H, W), measured in a cross-section of said air intake passage, is in the range from 1:1 to 1:0.10 and the tube comprises a constriction arranged in the internal passage of the tube such that the coverage of the passage is in the range from 0% to 95%. a base assembly comprising a chamber configured to receive a medication; and a mouthpiece assembly comprising air intake passages for supplying air into the inhaler, a rotation chamber for generating an aerosol of the medication, wherein the rotation chamber is in air communication with the air intake passages, a tube comprising an internal passage in air communication with the rotation chamber for discharging the aerosol of the medication and administering said aerosol to a patient; air intake passages for supplying air into the inhaler, a rotation chamber for generating an aerosol of the medication, wherein the rotation chamber is in air communication with the air intake passages, a tube comprising an internal passage in air communication with the rotation chamber for discharging the aerosol of the medication and administering said aerosol to a patient; wherein the base assembly and the mouthpiece assembly are configured such that the inhaler is capable of assuming an open configuration, in which access to the chamber of the base assembly is provided for inserting therein the medication, and a closed configuration, in which the chamber of the base assembly is in air communication with the rotation chamber of the mouthpiece assembly for transferring the medication from the chamber to the rotation chamber for forming out of it the aerosol of the medication, characterized in that at least one of the air intake passages and the tube of the mouthpiece assembly is selectable, and in that the air intake passages have a ratio of one of the transverse dimensions (H, W) to the other of the transverse dimensions (H, W), measured in a cross-section of said air intake passage, is in the range from 1:1 to 1:0.10 and the tube comprises a constriction arranged in the internal passage of the tube such that the coverage of the passage is in the range from 0% to 95%.