An inhaler for delivery of a powder-form inhalation formulation from a blister strip with a plurality of blister pockets containing the inhalation formulation in doses. The inhaler comprises a metallic piercing member with two piercing elements extending parallel to each other and inclined to the lid of a blister pocket to be punctured. To operate the inhaler, an air stream of ambient air can be sucked or delivered in order to discharge the respective dose from an opened blister pocket and to deliver the dose with the ambient air as an aerosol cloud.