A medicament delivery device, such as a dry powder inhaler (figure 1), locks after a predetermined number of doses have been dispensed. The locking mechanism comprises a resilient arm 51 which can engage with a formation (18, figure 2). A barrier member (20, figure 2) prevents this engagement until all the doses have been dispensed. Preferably, the barrier is transparent tape printed with incremental numbers corresponding to the number of doses. Towards the end of the tape is an aperture (21, figure 10) or series of slits (21, figure 11) which permit a protrusion 51a on the resilient arm to pass through the tape and engage with a window (18, figure 2) to lock the inhaler. The tape is dispensed to a collecting spool (40) having three protruding pegs (44) on an end plate (42). An actuator element 50 has arms 54 and 56 which engage with the pegs to rotate the spool when the actuator is depressed. The inhaler can lock with the actuator in the depressed position.
