The present invention relates to a medicament delivery device comprising a housing (16, 18), arranged to accommodate a medicament container (26)； a power unit (64) arranged inside said housing, said power unit comprising a plunger rod (118), a drive spring (120) operably arranged to act on the plunger rod (118) and, which is, upon activation, operably arranged to act on said medicament container (26), an actuator (90) comprising holding elements (94,100), capable of releasibly holding said plunger rod (118) with said drive spring (120) in a tensioned state, and an actuator sleeve (76) operably connected to said actuator (90) for releasibly locking said holding elements (94, 100) in a holding state； said medicament delivery device further comprising a medicament delivery member guard (34) slidably movable in said housing (16, 18) and arranged to act on said actuator sleeve (76) for setting said holding elements (94, 100) with said actuator sleeve (76) in a first activation state； an activator unit (130) arranged to be manually operated and which is operably connected to said plunger rod (118) for setting said holding elements (94, 100) with said actuator sleeve (76) in a second activation state, wherein said plunger rod (118) is released when both activation states are set. The invention is characterised in an adjuster element (150, 178) operably arranged between said plunger rod (118) and said activator unit (130), which adjuster element (150, 178) has a length dependent on the initial position of the stopper (28) in relation to the initial position of a proximal end of the plunger rod (118).本發明有關藥物輸送裝置，包含外殼(16、18)，被配置來容納藥物容器(26)；動力單元(64)，被配置在該外殼內側，該動力單元包含柱塞桿(118)、可操作地配置來作用在該柱塞桿(118)上且於啟動時係可操作地配置來作用在該藥物容器(26)上之驅動彈簧(120)、包含固持元件(94、100)而能夠以該驅動彈簧(120)於拉伸狀態中可釋放地固持該柱塞桿(118)的作動器(90)、及可操作地連接至該作動器(90)用於將該固持元件(94、100)可釋放地鎖定於固持狀態中之作動器套筒(76)；該藥物輸送裝置另包含藥物輸送構件防護件(34)，可於該外殼(16、18)中滑動地運動，且被配置來作用在該作動器套筒(76)上，用於以該作動器套筒(76)將該固持元件(94、100)設定於第一啟動狀態；啟動器單元(130)，被配置成可手動地操作，且其係可操作地連接至該柱塞桿(
