Actuator for an inhaler for delivering medicament by inhalation. The actuator includes a main body having a tubular member for receiving a canister containing medicament and having a valve stem extending therefrom, and an outlet assembly, as a part formed separately of the main body, having a mouthpiece for guiding medicament to the mouth of a user and a nozzle block for receiving the valve stem of the canister and delivering medicament from the canister into the mouthpiece. At least a part of the outlet assembly is configured so as to deform and optionally break on withdrawal of the outlet assembly from the main body so as to prevent re-use of the outlet assembly.