Inhaler

An inhaler comprising a housing which contains a blister strip having a plurality of blisters which contain powdered medicament for inhalation, a mouthpiece mounted on the housing through which the medicament is inhaled by a user, an outer cover which is mounted on the housing so that it pivots between a first, closed position in which the outer cover covers the mouthpiece, and a second, open position in which the mouthpiece is exposed, a blister piercing member, an indexing wheel for sequentially moving each blister into alignment with the blister piercing member, an actuator gear mounted for rotation about a first axis which is driven by the outer cover, and which comprises an actuator gear element, a drive gear for driving the indexing wheel, mounted for rotation about a second axis, which engages with the actuator gear element, wherein pivoting the outer cover from the closed position to the open position causes indexing and piercing of two blisters, characterized in that the gear ratio between the actuator gear element and the drive gear varies as they rotate during opening of the outer cover.