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.一種用以藉由提供有心軸螺帽(128；228)及彈簧鎖定螺帽(130；230)之劑量設定機構(104；204)來防止輸送少於藥物之預定最小劑量的方法及系統。該機構包含殼體(120；220)與位於該殼體中的劑量調撥組件(122)。該劑量調撥組件在劑量設定步驟期間可旋轉。該機構更包含位在該劑量調撥組件(122)內的驅動套筒(124；224)。該驅動套筒建構為在劑量施給步驟期間可驅動可旋轉心軸(126；226)。該心軸螺帽(128；228)耦合至該心軸(126；226)以及該彈簧鎖定螺帽(130；230)可移除地耦合至該驅動套筒(124；224)以及可旋轉地固定於該殼體(120；220)。在一配置中，在旋轉該劑量調撥組件(122)以選擇小於預定最小劑量的劑量時，該彈簧鎖定螺帽(130；230)允許該心軸螺帽(128；228)旋轉藉此防止該劑量被施給。
