A cartridge assembly for delivering a quantity of medication to bone marrow of a bone comprising a fluid reservoir (132； 132a) having a first end and a second end； a hollow, bone penetrating needle (160) releasably engaged with the first end of the fluid reservoir (132； 132a), the needle (160) operable to penetrate into the bone and bone marrow； a plunger assembly (82) including a plunger shaft (142) and a piston (144) slidably disposed in the fluid reservoir (132； 132a)； a drive connector (150) attached to the second end of the fluid reservoir (132； 132a) opposite from the bone penetrating needle (160)； and a portion of the plunger shaft (140) extending from the second end of the fluid reservoir (132； 132a), where the needle (160) is operable to be disengaged from the fluid reservoir (132； 132a) when the needle (160) has penetrated into the bone and bone marrow.
