A method and system for preventing delivery of less than a predetermined minimum dose of a medicament by providing a dose setting mechanism (104 204) having a spindle nut (128 228) and a sprung lock nut (130 230). The mechanism includes a housing (120 220) and a dose dial component (122) positioned in the housing. The dose dial component is rotatable during a dose setting step. The mechanism further includes a drive sleeve (124 224) positioned within the dose dial component (122). The drive sleeve is configured to drive a rotatable spindle (126 226) during a dose administration step. The spindle nut (128 228) is coupled to the spindle (126 226) and the sprung lock nut (130 230) is removably coupled to the drive sleeve (124 224) and rotationally fixed to the housing (120 220). In one arrangement when the dose dial component (122) is rotated to select a dose less than a preselected minimum dose the sprung lock nut (130 230) allows the spindle nut (128 228) to rotate thereby preventing the dose from being administered.
