The present invention relates to a single-dose dry powder inhaler comprising a base assembly comprising a chamber (14) configured for receiving a medication； and a mouthpiece assembly comprising air intake passages (25) for supplying air to the inhaler, a rotation chamber (26) for generating an aerosol of a medication, wherein the rotation chamber (26) is in air communication with the air intake passages (25), a tube (21C) comprising an internal passage in air communication with the rotation chamber (26) for discharging an aerosol of a medication and for 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 (14) of the base assembly is provided for inserting therein a medication, and a closed configuration, in which the chamber (14) of the base assembly is in air communication with the rotation chamber (16) of the mouthpiece assembly for transferring a medication from the chamber (14) to the rotation chamber (16) for forming out of it an aerosol of the medication, and wherein at least one of the air intake passages (25) and the tube (21C) of the mouthpiece assembly is selectable, and in that the air intake passages (25) have a ratio of one of the transverse dimensions (H, W) to the other of the transverse dimensions (H, W) in the range from 1:1 to 1:0.10 and the tube (21C) comprises a constriction (27) arranged in the internal passage of the tube such that the coverage of the passage is in the range from 0% to 95%. The present invention relates also to a method for adjusting a single-dose dry powder inhaler for administering a specific medication.
