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.
